20051206 Ver 1_Complete File_20050630

0 ?6
WA.Ts Michael F. Easley, Governor
?
?? G William G. Ross Jr., Secretary
C r North Carolina Department of Environment and Natural Resources
© -? Alan W. Klimek, P.E. Director
Division of Water Quality
August 24, 2005
Mr. Carl R. Dawson, Jr., PE, Public Works Director
City of Raleigh Public Works Department
P.O. Box 590
Raleigh, NC 27602-0590
Re: City of Raleigh Northshore and Brentwood Today Dam and Lake Rehabilitation, Wake County
DWQ #05-1206; USACE Action ID. No. 200421569
APPROVAL of 401 Water Quality Certification and Neuse River Buffer Rules
Dear Mr. Dawson:
Attached hereto is a copy of Certification No. 3529 issued to Carl R. Dawson, Jr. of City of Raleigh
Public Works Department, dated August 24, 2005. In addition, you should get any other federal, state or
local permits before you go ahead with your project including (but not limited to) Solid Waste, Sediment
and Erosion Control, Stormwater, Dam Safety, Non-discharge and Water Supply Watershed regulations.
If we can be of further assistance, do not hesitate to contact us.
Sincerely,
AWK/cbk
Klimek, P.E.
Attachments: Certificate of Completion
cc: U.S. Army Corps of Engineers, Raleigh Regulatory Field Office
Wilmington District, USACOE
Mike Horan, DWQ, Raleigh Regional Office
DLR Raleigh Regional Office
File Copy
Central Files
Jim Leumas, Senior Project Engineer, City of Raleigh, P.O. Box 590, Raleigh, NC 27602
Filename: 051206CORNorthshoreBrentwoodDamLakeRehab(Wa ke)401_IC
401 Oversight/Express Review Permits Unit
1650 Mail Service Center, Raleigh, North Carolina 27699-1650
2321 Crabtree Boulevard, Suite 250, Raleigh, North Carolina 27604
Phone: [phone]/ FAX [phone]/ Internet: htto://h2o.enr.state.nc.us/ncwetiands
None Caro na
aturaA
An Equal Opportunity/Affirmative Action Employer - 50% Recycled/l0% Post Consumer Paper
City of Raleigh Public Works Department
Page 2 of 4
August 24, 2005
i
NORTH CAROLINA 401 WATER QUALITY CERTIFICATION AND NEUSE RIVER BUFFER
RULES
THIS CERTIFICATION is issued in conformity with the requirements of Section 401 Public Laws 92-
500 and 95-217 of the United States and subject to the North Carolina Division of Water Quality (DWQ)
Regulations in 15 NCAC 21-1, Section .0500 and 15A NCAC 2N.0233 to Mr. Carl R. Dawson, Jr. of City of
Raleigh Public Works Department to fill or otherwise impact 0.56 acres of jurisdictional wetlands, 0.63
acres of open waters, 390 linear feet of stream and 84,942 square feet of buffers in the Neilse River Basin,
associated with the reconstruction of the dams and spillways, and excavation and reshaping of lake beds for
the Northshore and Brentwood Today Lakes in Wake County, North Carolina, pursuant to an application
filed on the 28t" day of June of 2005, and in additional correspondence received July 20, 2005.
The application and supporting documentation provides adequate assurance that the proposed work will
not result in a violation of applicable Water Quality Standards and discharge guidelines. Therefore, the
State of North Carolina certifies that this activity will not violate the applicable portions of Sections 301,
302, 303, 306, 307 of PL 92-500 and PL 95-217 if conducted in accordance with the application, the
supporting documentation, and conditions hereinafter set forth.
This approval is only valid for the purpose and design submitted in the application materials and as
described in the Public Notice. If the project is changed, prior to notification a new application for a new
Certification is required. If the property is sold, the new owner must be given a copy of the Certification
and approval letter and is thereby responsible for complying with all conditions of this Certification. Any
new owner must notify the Division and request the Certification be issued in their name. Should wetland
or stream fill be requested in the future, additional compensatory mitigation may be required as described
in 15A NCAC 21-1.0506 (h) (6) and (7). If any plan revisions from the approved site plan result in a
change in stream or wetland impact or an increase in impervious surfaces, the DWQ shall be notified in
writing and a new application for 401 Certification may be required. For this approval to be valid,
compliance with the conditions listed below is required.
Conditions of Certification:
1. Impacts Approved
The following impacts are hereby approved as long as all of the other specific and general
conditions of this Certification (or Isolated Wetland Permit) are met. No other impacts are
approved including incidental impacts:
Amount A roved Units Plan Location or Reference
Stream 390 feet Permit Narrative, page 4
404/CAMA Wetlands 0.56 acres Permit Narrative, page 4
Waters 0.63 acres Permit Narrative, page 4
Buffers 84,942 (square ft. Permit Narrative, page 11
Sediment and Erosion Control:
2. Erosion and sediment control practices must be in full compliance with all specifications
governing the proper design, installation and operation and maintenance of such Best
Management Practices in order to protect surface waters standards:
..
City of Raleigh Public Works Department
Page 3 of 4
August 24, 2005
a. The erosion and sediment control measures for the project must be designed, installed,
operated, and maintained in accordance with the most recent version of the North Carolina
Sediment and Erosion Control Planning and Design Manual.
b. The design, installation, operation, and maintenance of the sediment and erosion control
measures must be such that they equal, or exceed, the requirements specified in the most
recent version of the North Carolina Sediment and Erosion Control Manual. The devices
shall be maintained on all construction sites, borrow sites, and waste pile (spoil) projects,
including contractor-owned or leased borrow pits associated with the project.
c. For borrow pit sites, the erosion and sediment control measures must be designed, installed,
operated, and maintained in accordance with the most recent version of the North Carolina
Surface Mining Manual.
d. The reclamation measures and implementation must comply with the reclamation in
accordance with the requirements of the Sedimentation Pollution Control Act.
3. No waste, spoil, solids, or fill of any kind shall occur in wetlands, waters, or riparian areas beyond
the footprint of the impacts depicted in the 404/401 Permit Application. All construction activities,
including the design, installation, operation, and maintenance of sediment and erosion control Best
Management Practices, shall be performed so that no violations of state water quality standards,
statutes, or rules occur;
4. Sediment and erosion control measures shall not be placed in wetlands or waters to the maximum
extent practicable. If placement of sediment and erosion control devices in wetlands and waters is
unavoidable, they shall be removed and the natural grade restored within six months of the date that
the Division of Land Resources has released the project;
5. The NC Wildlife Resources Commission (Ms. Shari Bryant) must be contacted before any lowering
of the water level occurs to get their concurrence with respect to impacts on fishery resources.
6. All spoil must be disposed on in upland sites and outside the protected riparian buffer zones.
Continuing Compliance:
Mr. Carl R. Dawson, Jr. and City of Raleigh Public Works Department, shall conduct construction
activities in a manner consistent with State water quality standards (including any requirements resulting
from compliance with section 303(d) of the Clean Water Act) and any other appropriate requirements of
State law and federal law. If the Division determines that such standards or laws are not being met
(including the failure to sustain a designated or achieved use) or that State or federal law is being violated,
or that further conditions are necessary to assure compliance, the Division may reevaluate and modify this
Certification to include conditions appropriate to assure compliance with such standards and requirements
in accordance with 15A NCAC 2H.0507(d). Before modifying the Certification, the Division shall notify
Mr. Carl R. Dawson, Jr. and/or City of Raleigh Public Works Department and the US Army Corps of
Engineers, provide public notice in accordance with 15A NCAC 2H.0503 and provide opportunity for
public hearing in accordance with 15A NCAC 2H.0504. Any new or revised conditions shall be provided
to Mr. Carl R. Dawson, Jr. and/or City of Raleigh Public Works Department in writing, shall be provided
to the United States Army Corps of Engineers for reference in any Permit issued pursuant to Section 404 of
the Clean Water Act, and shall also become conditions of the 404 Permit for the project;
8. Certificate of Completion
Upon completion of all work approved within the 401 Water Quality Certification or applicable
Buffer Rules, and any subsequent modifications, the applicant is required to return the attached
certificate of completion to the 401/Wetlands Unit, North Carolina Division of Water Quality,
1650 Mail Service Center, Raleigh, NC, 27699-1650.
City of Raleigh Public Works Department ...
Page 4 of 4
August 24, 2005
9. Live or fresh concrete shall not be allowed to contact waters of the State until it has dried to
prevent violations of DWQ's pH water quality standard and aquatic toxicity.
Neuse River Basin Impacts:
10. Impacts to the riparian buffer around these lakes and tributary streams are also hereby approved.
Any buffer area impacted for construction access must be stabilized and revegetated within 60
days of the completion of the project. Any trees that must be removed for this work (except for
trees that need to be removed for dam stability concerns) must be replanted by the end of the next
fall-winter planting season
Also, this approval to proceed with your proposed impacts or to conduct impacts to waters as
depicted in your application shall expire upon expiration of the 404 or CAMA Permit.
If this Certification is unacceptable to you, you have the right to an adjudicatory hearing upon written
request within sixty (60) days following receipt of this Certification. This request must be in the form of a
written petition conforming to Chapter 150B of the North Carolina General Statutes and filed with the
Office of Administrative Hearings, 6714 Mail Service Center, Raleigh, N.C. 27699-6714. If
modifications are made to an original Certification, you have the right to an adjudicatory hearing on the
modifications upon written request within sixty (60) days following receipt of the Certification. Unless
such demands are made, this Certification shall be final and binding.
This is the 20' day of August 2005.
DIVISION OF WATER QUALITY
AWK/cbk
1.. 01
imek,
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US Army Corps
Of Engineers
Wilmington District
JR@[RoyR
D
PUBLIC NOTICE 1U1 2 1 2005
DENR -WATER QUgLITy
WRZ8 AND 3TORMWATER BRANCH
Issue Date: July 15, 2005
Comment Deadline: August 15, 2005
Corps Action ID #: 200421569
All interested parties are hereby advised that the Wilmington District, Corps of Engineers
(Corps) has received an application for work within jurisdictional waters of the United
States. Specific plans and location information are described below and shown on the
attached plans. This Public Notice and all attached plans are also available on the
Wilmington District Web Site at www.saw.usace.army.mil/wetlands
Applicant: City of Raleigh
Attn: Mr. Carl R. Dawson Jr.
Public Works Department
Post Office Box 590
City of Raleigh, NC 27602-0590
Authority
The Corps will evaluate this application and decide whether to issue, conditionally issue,
or deny the proposed work pursuant to the applicable procedures of Section 404 of the
Clean Water Act.
Location
The project, Northshore and Brentwood Today Dam and Lake Rehabilitation, is located
on the north and south of New Hope Church Road, approximately 0.5 miles west of
Capital Boulevard (U.S. Highway 1), in Raleigh, Wake County, North Carolina.
Coordinates (in decimal degrees) for the site are 35.8370°North, 78.5875 ° West. The
project site contains an unnamed tributary to Marsh Creek, and adjacent wetlands, in the
Neuse River Basin (8-Digit Cataloging Unit 03020201).
Existing Site Conditions
Northshore and Brentwood Today are the second and third lakes in a series of four lakes
that occurs along a 2-mile stretch of an unnamed tributary to Marsh Creek. Northshore
Lake is approximately 7.68 acres in size and Brentwood Today Lake is approximately 4.4
acres in size. Both lakes were originally constructed more than 50 years ago as amenities
to the surrounding residential developments. Below the lowest lake in the series, the
tributary flows into Marsh Creek, which in turn flows into Crabtree Creek about two
miles downstream. The land use in the area immediately adjacent to the lakes is
primarily medium to high-density residential subdivisions. A substantial portion of the
watershed that drains into the lakes also consists of commercial and industrial areas
located along the Capital Boulevard corridor.
Both Northshore Lake and Brentwood Today Lake have been experiencing significant
sediment deposition over the last several decades, due in large part to development
activities that have occurred in the drainage basin. The deepest portions of both lakes
have an estimated 3-5 feet of sediment buildup, and the upper ends of the fakes have
become very shallow. The accumulation of sediment has also led to the development of
wetland areas in the headwater regions of both lakes. Additionally, both lakes have
received increasing amounts of stormwater runoff as the extent of impervious surface has
increased in their watershed. Spillways for both lakes have also significantly eroded and
are in poor condition. The City has stated that both dams have been a safety concern for
more than 20 years.
Applicant's Stated Purpose
As stated by the applicant, the project has three primary objectives: 1) to address NC
Dam Safety concerns for long-term stability and downstream protection; 2) to identify
opportunities for water quality enhancement of the watershed supplemental to ongoing
City efforts; and 3) to preserve property value for the neighborhoods surrounding the
lakes.
Project Description
The project involves the reconstruction of the dam and spillway structures for Northshore
and Brentwood Today Lakes, as well as excavation and reshaping activities within both
lakebeds. For Northshore Lake, the dam is proposed to be improved to meet dam safety
requirements. The primary spillway structure would be enlarged and protrude into the
lakebed. A 150-foot weir at elevation 265.9 would be constructed along the front edge of
the spillway in order to pass expected high flows. The spillway would be notched for 25
feet down to an elevation of 263 feet, and 2-inch water-quality drawdown holes Would be
placed at elevation 262. The drawdown holes would pass the normal daily flows' and
establish the new normal pool of the lake at 262 feet, a drop of 2.5 feet from the existing
normal pool of the lake. The work would result in a 1.5-foot increase in the flood storage
capacity of the structure.
Approximately 1.5 acres of the lakebed would be dredged to remove accumulated
sediment. Most of the dredging would occur in upper portions of the lakebed and around
the perimeter of the lake. The dredging would allow the overall surface area of the lake
to remain approximately equal to current conditions. Plans also call for the construction
of a 0.8-acre sediment pool at the upper end of the lake just south of Comstock Road.
The pool would be constructed in a spot that currently contains a house that would have
to be removed. The sediment pool would be constructed to allow periodic maintenance
dredging to remove sediment build-up. Additionally, a 0.7-acre headwater wetland
2

would be constructed just downstream of the sediment pool to help filter nutrients and
contaminants. Small plunge pool structures are also proposed at the outlets of existing
outfalls and channels to provide treatment for sediment and contaminant runoff.
Impacts to Waters of the U.S. associated with the rehabilitation to Northshore Lake
include the temporary disturbance of 1.5 acres of lakebed for dredging, and the
permanent loss of 0.08 acre of open water for construction of the spillway device. The
reduction of the normal pool of the lake and construction of the sediment pool would also
lead to the loss of 0.46 acre of riparian forested wetland, 0.03 acre of fringe wetland, 0.51
acre of open water, and 260 linear feet of perennial stream channel that is currently
inundated by the lake.
For Brentwood Today Lake the dam would be upgraded with a new spillway. The
spillway would have a 100-foot weir at elevation 245.2, with a 20-foot notch cut down to
242 feet. No change in water level is proposed to the lake. Approximately 3 acres of
lakebed would be dredged to remove accumulated sediment, and a 0.4-acre sediment pool
would be created where a primary tributary enters the lake along the eastern side. A
smaller sediment pool is also proposed just downstream of New Hope Church Road, and
a plunge pool would be constructed on the western side of the lake. The majority of
existing wetlands within the lake would be preserved.
Impacts to Waters of the U.S. associated with the rehabilitation to Brentwood Today
Lake include the temporary disturbance of 3 acres of lakebed for dredging, and the
permanent loss of 0.04 acre of open water for construction of the spillway. Spillway
construction will also impact 50 linear feet of unstable perennial stream channel that has
developed in the location of the eroded spillway. The construction of the sediment pool
at the tributary draining into the eastern side of the lake would also lead to the loss of
0.07 acre of forested wetlands and 80 linear feet of perennial stream channel.
The impact to jurisdictional areas resulting from the rehabilitation of both lakes totals 4.5
acres of temporary disturbance due to dredging, the loss of 0.63 acre of open waters, 0.53
acre of forested wetlands, 0.03 acre of fringe wetlands, and 390 linear feet of stream
channel. Plans included with this notice that show the project details as well as the
details for impacted streams and wetlands.
The applicant does not propose specific mitigation for impacts resulting from the project
because one of the primary purposes of the project is to improve water quality.
Additionally, as part of the project, a 0.7-acre forested wetland is proposed to be created
at the upper end of Northshore Lake, and it is expected that more than 0.5 acres of
wetlands will develop in portions of the exposed lakebed once the water level is lowered.
Other Required Authorizations
This notice and all applicable application materials are being forwarded to the appropriate
State agencies for review. The Corps will generally not make a final permit decision
until the North Carolina Division of Water Quality (NCDWQ) issues, denies, or waives
3
State certification required by Section 401 of the Clean Water Act (PL 92-500). The
receipt of the application and this public notice in the NCDWQ Central Office in Raleigh
serves as application to the NCDWQ for certification. A waiver will be deemed to occur
if the NCDWQ fails to act on this request for certification within sixty days ',of the date of
the receipt of this notice in the NCDWQ Central Office. Additional information
regarding the Clean Water Act certification may be reviewed at the NCDWQ Central
Office, 401 Oversight and Express Permits Unit, 2321 Crabtree Boulevard, Raleigh,
North Carolina 27604-2260. All persons desiring to make comments regarding the
application for certification under Section 401 of the Clean Water Act should do so in
writing delivered to the North Carolina Division of Water Quality (NCDWQ), 1650 Mail
Service Center, Raleigh, North Carolina, 27699-1650 Attention: Ms Cyndi karoly by
August 8, 2005.
Essential Fish Habitat
This notice initiates the Essential Fish Habitat (EFH) consultation requirements of the
Magnuson-Stevens Fishery Conservation and Management Act. The Corps' initial
determination is that the proposed project will not adversely impact EFH or associated
fisheries managed by the South Atlantic or Mid Atlantic Fishery Management Councils
or the National Marine Fisheries Service.
Cultural Resources
The Corps has consulted the latest published version of the National Register of Historic
Places and is not aware that any registered properties, or properties listed as being
eligible for inclusion therein are located along the project corridor or will be affected by
the proposed work. Presently, unknown archeological, scientific, prehistoric, or
historical data may be located within the project area and/or could be affected by' the
proposed work.
Endangered Species
The Corps has reviewed the project area, examined all information provided by the
applicant and consulted the latest North Carolina Natural Heritage Database. Based on
available information, the Corps has determined pursuant to the Endangered Species Act
of 1973, that the proposed project will have no effect on federally listed endangered or
threatened species or their formally designated critical habitat.
Evaluation
The decision whether to issue a permit will be based on an evaluation of the probable
impacts, including cumulative impacts, of the proposed activity on the public interest.
That decision will reflect the national concern for both protection and utilization of
important resources. The benefit which reasonably may be expected to accrue from the
proposal must be balanced against its reasonably foreseeable detriments. All factors
which may be relevant to the proposal will be considered including the cumulative effects
4
thereof; among those are conservation, economics, aesthetics, general environmental
concerns, wetlands, historic properties, fish and wildlife values, flood hazards, flood plain
values (in accordance with Executive Order 11988), land use, navigation, shoreline
erosion and accretion, recreation, water supply and conservation, water quality, energy
needs, safety, food and fiber production, mineral needs, considerations of property
ownership, and, in general, the needs and welfare of the people. For activities involving
the discharge of dredged or fill materials in waters of the United States, the evaluation of
the impact of the activity on the public interest will include application of the
Environmental Protection Agency's 404(b)(1) guidelines.
Commenting Information
The Corps is soliciting comments from the public; Federal, State and local agencies and
officials, including any consolidate State Viewpoint or written position of the Governor;
Indian Tribes and other interested parties in order to consider and evaluate the impacts of
this proposed activity. Any comments received will be considered by the Corps to
determine whether to issue, modify, condition or deny a permit for this proposal. To
make this decision, comments are used to assess impacts on endangered species, historic
properties, water quality, general environmental effects and the other public interest
factors listed above. Comments are used in the preparation of an Environmental
Assessment (EA) and/or an Environmental Impact Statement (EIS) pursuant to the
National Environmental Policy Act (NEPA). Comments are also used to determine the
need for a public hearing and to determine the overall public interest of the proposed
activity.
Any person may request, in writing, within the comment period specified in this notice,
that a public hearing be held to consider the application. Requests for public hearings
shall state, with particularity, the reasons for holding a public hearing. Requests for a
public hearing shall be granted, unless the District Engineer determines that the issues
raised are insubstantial or there is otherwise no valid interest to be served by a hearing.
Written comments pertinent to the proposed work, as outlined above, will be received
by the Corps of Engineers, Wilmington District, until 5pm, August 15, 2005. Continents
should be submitted to Todd Tugwell, Raleigh Regulatory Field Office, 6508 Falls of the
Neuse Road, Suite 120, Raleigh, NC 27615.
5
Figure 1
Project Vicinity Map February2005 ONE cohirnNYlhrany soturlvnr-
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Page 2
15 August 2005
Northshore and Brentwood Today
Action ID No. 200421569
... o F f-A ?.. dnnd in the nnner end of Northshore Lake and it is expected that more than 0.5 acres of
oS-
North Carolina Wildlife Resources Commission C
Richard B. Hamilton, Executive Director
MEMORANDUM
TO: Todd Tugwell, Raleigh Regulatory Field Office
U.S. Army Corps of Engineers
FROM: Shari L. Bryant, Pied ont Region Coordinator
Habitat Conservation Program
DATE: 15 August 2005
V@[Ruw4b
AUG 1 9 2005
A? 1],QDEN, R - WATER QUALITY
y l Ode CJJ?STO= P.hv4 ??CH
SUBJECT: Public Notice for City of Raleigh, Northshore and Brentwoo ay am ahc????
Rehabilitation, Wake County, North Carolina. Action ID No. 200421569
Biologists with the North Carolina Wildlife Resources Commission (NCWRC) have reviewed the
subject document and are familiar with the habitat values of the area. Our comments are provided in
accordance with provisions of the Clean Water Act of 1977 (as amended), Fish and Wildlife Coordination
Act (48 Stat. 401, as amended; 16 U.S.C. 661-667d), and North Carolina General Statutes (G.S. 113-131
et seq.).
The applicant proposes to reconstruct the dam and spillway and to excavate and reshape the lake
beds for Northshore and Brentwood Today Lakes. These lakes are located on an unnamed tributary to
Marsh Creek which is a tributary to Crabtree Creek in the Neuse River basin There are records for the
federal species of concern and state endangered Atlantic pigtoe (Fusconaia madom), the federal species of
concern and state significantly rare Carolina madtom (Noturus f iriosus), the state threatened creeper
(Strophilus undulatus) and triangle floater (Alasmidonta undulata), and the state special concern notched
rainbow (Villosa constricta) in Crabtree Creek.
The Northshore Lake dam will be improved to meet dam safety requirements and the primary
spillway structure would be enlarged. Normal pool would be established 2.5 feet below the existing
normal pool to create a 1.5 foot increase in flood storage. Approximately 1.5 acres would be dredged in
the upper portions and perimeter of the lake. A 0.8 acre sediment pool would be constructed in the upper
end of the lake and a 0.7 acre headwater wetland would be constructed downstream of the sediment pool.
The Brentwood Today Lake dam would be upgraded with a new spillway. Approximately 3 acres of lake
would be dredged and a 0.4 acre sediment pool would be created where a primary tributary enters the
lake.
The project will result in temporary disturbance of 4.5 acres due to dredging, and the loss of 0.63
acre of open water, 0.53 acre of forested wetlands, 0.03 acre of fringe wetlands and 390 linear feet of
stream channel. The project is expected to improve water quality. The applicant proposes to create a 0.7
Mailing Address: Division of Inland Fisheries - 1721 Mail Service Center - Raleigh, NC 27699-1721
Telephone: [phone] - Fax: [phone]

Page 2
15 August 2005
Northsliore and Brentwood Today
Action ID No. 200421569
acre forested wetland in the upper end of Northshore Lake and it is expected that more than 0.5 acres of
wetlands will develop in the exposed lake bed once the water level is lowered. The applicant does not
propose specific mitigation. One of the primary purposes for the project is to improve water quality and
the project will result in the creation of wetland habitats.
It is unclear whether the sediment pools will be constructed in areas that are already impounded
or whether freo-flowing stream channels will be impounded or excavated to create the sediment pools.
We would prefer the sediment pools be constructed in areas of the lake that are currently impounded. If
the applicant proposes to impound or excavate free-flowing stream channel to create these sediment pools
this will remove the natural functionality of the stream and we feel that mitigation for impact to stream
channels should be performed according to the Stream Mitigation Guidelines (April 2003).
We will not object to the project provided the following conditions are incorporated into the
permit to reduce impacts to fish and wildlife resources.
1. We recommend that all remaining wetlands and streams on the site should be protected from
additional impacts by placing them in a permanent conservation easement to prohibit filling,
draining, flooding, and excavation.
2. Should water levels in the lakes need to be lowered to perform the dam construction and
dredging, we request that the lakes be lowered and the work completed, if possible, between 15
October and 15 March to minimize fish stress and the chance of a fish kill within the lakes.
3. Should the lakes remain at normal pool during the dredging, we request that dredging not occur
between 15 March and 15 July. Fish spawn in spring and young fish occupy near shore habitats
in early summer. Prohibiting dredging during this time period will minimize impacts to the fish
population within the lakes.
4. All sediment removed is deposited in upland areas or is disposed of at an approved facility.
5. Specialized efforts and techniques are implemented to reduce sediment runoff from construction
activities. Excessive silt and sediment loads can have numerous detrimental effects on aquatic
resources including destruction of spawning habitat, suffocation of eggs, and clogging of gills of
aquatic species.
6. Concrete is toxic to aquatic life and should not be allowed to come in contact with surface waters
until cured.
7. Should free-flowing stream channels be impacted by construction of the sediment pools, a
mitigation plan should be submitted and approved before impacts occur
Thank you for the opportunity to comment on this project. If we can provide further assistance,
please contact our office at (336) 449--7625.
cc: Cyndi Karoly, DWQ
Triage Check List
Ci} t d P?1 e i h- N cif 'rl? S0Y ?-
7 I ProJ'cEt Name: e?? ??? o n 1o cwt, Clam .? ?a ?e r4ak
Dale, .
DWQ#: O G l ZO
County: WM-e
To: ? ARO Kevin Barnett ? WaRO Tom Steffens and Kyle Barnes
? FRO Ken Averitte ? WiRO Noelle Lutheran
?, MRO Alan Johnson ? WSRO Daryl Lamb
Lf/ RRO Mike Horan
From: Telephone : (919)7 1 ; - a 72
The file attached is being forwardedto dour for your evaluation.
Please call if you need asst}stance.
? Stream length impacted
? Stream determination
? Wetland determination and distance to blue-line surface,waters on USFW topo maps
? Minimization/avoidance issues
? Buffer Rules (Meuse, Tar-Pamlico, Catawba, Randleman)
? Pond fill
? Mitigation Ratios
? Ditching
? Are the stream and or wetland mitigation sites available and viable?
? Check drawings for accuracy
? Is the application consistent with pre-application meetings?
? Cumulative impact concern
Comments:

(-)S-
?'rA
4 s?,? it

June 29, 2005
Ms. Cyndi Karoly
NCDENR
Division of Water Quality
401/Wetlands Certification Unit
1650 Mail Service Center
Raleigh, NC 27699-1650
RE: Northshore and Brentwood Today Lakes Rehabilitation Project
Raleigh, North Carolina
Dear Ms. Karoly:
Enclosed are two (2) copies of an individual permit application, under Section 404 of the Clean
Water Act (CWA), for the Northshore and Brentwood Today Lakes Rehabilitation Project. The
City of Raleigh contracted HDR Engineering, Inc. of the Carolinas (HDR) to perform a study of
these lakes, prepare alternative recommendations, and coordinate public input on the
rehabilitation of these facilities. This permit application includes this cover letter, ENG Form
4345, associated attachments, permit impact sheets, and a list of property owners as specified in
the application requirements. The application is being submitted for CWA Section 404 permit
approval, CWA Section 401 certification, and Neuse Buffer certification under the Neuse River
Riparian Buffer Rules.
Although this plan and design are conceptual in nature, the impacts are primarily related to the
repair and rehabilitation of the spillways and dams, and the reduction of water level in
Northshore Lake. The design of the spillway structures and the reduction of water levels have
reached the point where an impact estimate can be made. Therefore, the City is submitting this
permit application for your review and feedback in order to gain input and comments that will be
incorporated into the final design and, if needed, permit re-application. Additional design will be
occurring as the project continues, but should not significantly change the impacts discussed
below.
OFFICES • 222 WEST HARGETT STREET • POST OFFICE BOX 590 • RALEIGH, NORTH CAROLINA 27602
RECYCLLD PAPER
Ms. Cyndi Karoly
June 29, 2005
Page Two
Please contact me at telephone number 890-3931 if I may answer any questions concerning this
application or be of further assistance.
Sincerely,

James K. Leumas, P. E.
Senior Project Engineer
JKL/
Enclosures
cc: Mr. Carl R. Dawson, Jr., P. E.
Mr. H. Daniel Bowden, P. E.
Ms. Veronica L. High, E. I.
Mr. Todd Tugwell
Mr. Ronald A. Geiger, P. E.

June 29, 2005
Mr. "Todd Tugwell, Project Manager
U.S. Army Corps of l;ngineers
Raleigh Regulatory Office
6508 Falls of Neuse Road - Suite 120
Raleigh, NC 27615
RE: Northshore and Brentwood Today Lakes Rehabilitation Project
Raleigh, North Carolina
Dear Mr. Tugwell:
Enclosed is an individual permit application, under Section 404 of the Clean Water Act (CWA),
for the Northshore and Brentwood Today Lakes Rehabilitation Project. The City of Raleigh
contracted HDR Engineering, Inc. of the Carolinas (HDR) to perform a study of these lakes,
prepare alternative recommendations, and coordinate public input on the rehabilitation of these
facilities. This permit application includes this cover letter, ENG Form 4345, associated
attachments, permit impact sheets, and a list of property owners as specified in the application
requirements. The application is being submitted for CWA Section 404 permit approval, CWA
Section 401 certification, and Neuse Buffer certification under the Neuse River Riparian Buffer
Rules.
Although this plan and design are conceptual in nature, the impacts are primarily related to the
repair and rehabilitation of the spillways and dams, and the reduction of water level in
Northshore Lake. The design of the spillway structures and the reduction of water levels have
reached the point where an impact estimate can be made. Therefore, the City is submitting this
permit application for your review and feedback in order to gain input and comments that will be
incorporated into the final design and, if needed, permit re-application. Additional design will be
occurring as the project continues, but should not significantly change the impacts discussed
below.
li I
II I
III II
Mr. 1 odd I ugwell
June 29, 2005
Page "Two
Please contact me at telephone number 890-3931 if 1 may answer any questions concerning this
application or be of further assistance.
Sincerely,
Ll, .
James K. Leumas, P. E.
Senior Project Engineer
;II III
II II
I
I II
II II
; III
I? ill
JKL/
Enclosures
cc: Mr. Carl R. Dawson, Jr., P. E.
Mr. H. Daniel Bowden, P. E.
Ms. Veronica L. High, E. L
Ms. Cyndi Karoly
Mr. Ronald A. Geiger, P. E.
I
APPLICATION FOR DEPARTMENT OF THE ARMY PERMIT ( OMB APPROVAL NO. 0710-0003
/33 CFR 3251 Expires December 31, 2004
The Public burden for this collection of information is sestimated to average 10 hours per response, although the majority of applications should require
5 hours or less. This includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and
completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of
information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Service Directorate of Information
Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302; and to the Office of Management and Budget,
Paperwork Reduction Project (0710-0003), Washington, DC 20503. Respondents should be aware that notwithstanding any other provision of law,
no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control
number. Please DO NOT RETURN your form to either of those addresses. Completed applications must be submitted to the District Engineer having
jurisdiction over the location of the proposed activity.
PRIVACY ACT STATEMENT
Authorities: Rivers and Harbors Act, Section 10, 33 USC 403; Clean Water Act, Section 404, 33 USC 1344; Marine Protection , Research and
Sanctuaries Act, 33 USC 1413, Section 103. Principal Purpose: Information provided on this form will be used in evaluating the application for a
permit. Routine Uses: This information may be shared with the Department of Justice and other federal, state, and local government agencies.
Submission of requested information is voluntary, however, if information is not provided the permit application cannot be evaluated nor can a permit
be issued.
One set of original drawings or good reproducible copies which show the location and character of the proposed activity must be attached to this
application (see sample drawings and instructions) and be submitted to the District Engineer having jurisdiction over the location of the proposed
activity. An application that is not completed in full will be returned.
1. APPLICATION NO. 12. FIELD OFFICE CODE 13. DATE RECEIVED 14. DATE APPLICATION COMPLETED
11TEMS BELOW TO BE FILLED BY APPLICANT)
5. APPLICANT'S NAME S. AUTHORIZED AGENT'S NAME AND TITLE tnn ngenr a not tequitedl
Carl R. Dawson Jr., PE, Public Works Director
City of Raleigh, Public Works Department
6. APPLICANT'S ADDRESS 9. AGENT'S ADDRESS
City of Raleigh, Public Works Department
PC Box 590 Raleigh, NC 27602-0590
7. APPLICANT'S PHONE NOS. WIAREA CODE 10. AGENT'S PHONE NOS. W/AREA CODE
a. Residence a. Residence
b. Business 919-890-3030 I b. Business
1 1 . STATEMENT OF AUTHORIZATION
I hereby authorize, to act in my behalf as my agent in the processing of this application and to
rurnish, upon request, supplemental information in support of this permit application.
APPLICANT'S SIGNATURE DATE
NAME. LOCATION AND DESCRIPTION OF PROJECT OR ACTIVITY
12. PROJECT NAME OR TITLE tsc msit-oons.
Northshore and Brentwood Today Dam and Lake Rehabilitation
13. NAME OF WATERBODY, IF KNOWN otnppl,cbivcl 114. PROJECT STREET ADDRESS titnppbcnble)
Northshore Lake and Brentwood Today Lake, both on the New Hope
to Marsh Creek
15. LOCATION OF PROJECT
Wake County
COUNTY
North Carolina
STATE
16. OTHER LOCATION DESCRIPTIONS, IF KNOWN, tserinstrucoonsl
Northshore Lake Dam coordinates: Latitude 35 deg. 50 min. 13 sec. / Longitude 78 deg. 35 min. 16 sec.;
Brentwood Today Lake Dam coordinates: Latitude 35 deg. 49 min. 56 sec. / Longitude 78 deg. 35 min. 24 sec.
17. DIRECTIONS TO THE SITE
Take 1-440 Beltline to Capital Boulevard, proceed north on Capital approximately 2 miles to New Hope Church Road, turn left on New Hope
Church, after -1/4-mile you will pass Deana Lane on the right, Northshore Lake is then immediately to your north (right) and Brentwood Today
Lake is to your south (left)
NG FORM 4345, Jul 97 EDITION OF FEB 94 IS OBSOLETE. (Proponent: CECW-OR)
18. Nature of Activity (DescriFwion of pro;ecl, include all fcvtures)
This activity includes repair and rehabilitation of Northshore and Brentwood Today dams and spillways, dredging of both lakes, and lowering of
the water level in Northshore Lake for flood control. [See attachment]
19. Project Purpose (Describe the rarson or purpose of the project, sce instructions)
These two lakes are privately-owned earthen dams with a recent history of overtopping during high flood events. Both dams and spillways are
in need of repair. The lakes are surrounded by residential homes and apartments that are subject to flooding. New Hope Church Road, just
downstream of Northshore Lake, could wash out due to an overtopping event. Both lakes have filled in with sediment over the past several
decades, thereby decreasing water quality. [See attachment]
USE BLOCKS 20-22 IF DREDGED AND/OR FILL MATERIAL IS TO BE DISCHARGED
20. Reason(s) for Discharge
Discharges are mainly related to the repair and rehabilitation of the dams and spillways. Some additional discharges will be associated with the
sediment pool construction and establishment of fringe wetlands around the lakes. [See attachment]
21. Type(s) of Material Being Discharged and the Amount of Each Type in Cubic Yards
[See attachment]
22. Surface Area in Acres of Wetlands or Other Waters Filled (see instructions)
[See attachment]
23. Is Any Portion of the Work Already Complete? Yes No X IF YES, DESCRIBE THE COMPLETED WORK
24. Addresses of Adjoining Property Owners, Lessees, Etc., Whose Property Adjoins the Waterbody (If more than can be entered here,
please attach a supplemental list).
See attached list
25. List of Other Certifications or Approvals/Denials Received from other Federal, State or Local Agencies for Work Described in This Application.
AGENCY TYPE APPROVAL' IDENTIFICATION NUMBER DATE APPLIED DATE APPROVED DATE DENIED
.N
ould include but is not restricted to zoning, building and flood plain permits
26. Application is hereby made for a permit or permits to authorize the work described in this application. I certify that the information in this
application is complete and accurate. I further certify that I possess the authority to undertake the work described herein or am acting as the
duly authorized e o the applicant.
-,75/61'
SIGNATURE OF APPL ANT DATE SIGNATURE OF AGENT DATE
The application must be signed by the person who desires to undertake the proposed activity (applicant) or it may be signed by a duly
authorized agent if the statement in block 11 has been filled out and signed.
18 U.S.C. Section 1001 provides that: Whoever, in any manner within the jurisdiction of any department or agency of the United States
knowingly and willfully falsifies, conceals, or covers up any trick, scheme, or disguises a material fact or makes any false, fictitious or
fraudulent statements or representations or makes or uses any false writing or document knowing same to contain any false, fictitious or
fraudulent statements or entry, shall be fined not more than $10,000 or imprisoned not more than five years or both.
Northshore and Brentwood Today Dam and Lake Rehabilitation
List of Permit Application Attachments
Permit Narrative (with Photographs)
Figures 1-7 (includes Project Vicinity Map)
Preliminary Spillway Drawings Q figures)
Email Communication with Becky Fox of the USEPA
Technical Memorandum No. 4 (Water Quality Evaluation of Conceptual Plans)
List of Adjacent Property Owners
Northshore and Brentwood Today Dam and Lake Rehabilitation Project
Section 404 Permit and Section 401/Neuse Buffer Certification Narrative
The narrative below is a thorough description of the project. Under each heading, the
corresponding item from ENG Form 4345 is listed in parentheses if applicable. For
continuity and readability reasons, the items are not necessarily in the order they occur in
the permit, and additional items are included for justification of the project.
Project Background and Purpose (Item 19)
There are a series of four lakes along the New Hope tributary to Marsh Creek and
Crabtree Creek: an unnamed lake, Northshore Lake, Brentwood Today Lake, and
Beaman Lake. The dam at Beaman Lake was breached several years ago and
reconstruction was recently completed to restore the dam embankment and install
features to improve water quality, including constructed wetlands.
This Project includes Northshore Lake and Brentwood Today Lake, which are located in
the City of Raleigh (City) near New Hope Church Road and west of U.S. Highway 1
(Capital Blvd.) as shown in Figure 1. The dams at both Lakes were identified as small,
high hazard dams in a report by Titan Atlantic dated July 20, 2004. Furthermore, the
spillways at both Lakes have been a safety concern for over 20 years. The dams have
been overtopped several times in recent years, causing flooding in the surrounding
residential area. There is also concern that New Hope Church Road, located just
downstream of Northshore Dam, has the potential to wash out during an overtopping
event.
In addition to safety concerns, development in the drainage basin over the last several
decades has created a significant amount of runoff and sedimentation entering these
lakes. Both Northshore and Brentwood Today have an estimated 3-5 feet of sediment in
their lower, deeper areas, and are very shallow in the upper ends with less than a foot of
water in some areas. Peninsula wetlands have been created in the headwater regions of
both lakes through accumulation of sediment. Algae and other noxious plants are present
throughout the lakes, but are concentrated in these shallow upper-headwater areas.
In 2004, the City of Raleigh (City) made a commitment to evaluate the potential of
rehabilitating the Northshore Lake and the Brentwood Today Lake dams and spillways to
minimize and/or prevent flooding to the neighboring property owners as well as improve
public safety downstream. The analysis of these two lakes was driven by three primary
objectives:
1) Address NC Dam Safety concerns for long-term stability and downstream
protection
2) Identify opportunities for water quality enhancement of the watershed
supplemental to ongoing City efforts
3) Preserve property value for the neighborhoods surrounding these lakes.
Northshore do Brentwood Today Lakes Page 2 of 15
4041401 Permit Application Narrative
The underlying goal for this effort is to provide a project that addresses these objectives
while achieving public support and meeting the goals of the City of Raleigh's Storm
Water Program. The planning process provided the basis for conceptual layouts for
rehabilitating the dam structures while also increasing water storage capacities and water
quality benefits. The conceptual layouts, discussed in the alternatives analysis section,
were produced with City input and presented for public comment. This planning process
provided a recommended plan comprising dam safety and water quality benefits. Both
lakes are located within the Marsh Creek watershed, which exhibits serious nutrient-
loading problems. This concept would help to reduce some of this nutrient loading as
discussed below.
Project Description (Item 18)
Although two separate lakes, the recommended improvements to these facilities are being
proposed in conjunction due to the overall purpose of this project. The analysis of
alternatives and development of a recommended plan were performed using a watershed
approach to the water quality issues, while looking individually at the project components
such as each dam and spillway. This plan development included incorporation of the
available flood control capacity of Northshore Lake, and the water quality improvements
of Beaman Lake to yield an overall approach for the New Hope tributary watershed.
Northshore Lake (Figure 2)
The Northshore Lake recommended plan is focused on long-term aquatic habitat
and nutrient-removal improvements, in addition to the required dam safety
improvements. An approximate 0.8-acre sediment pool is proposed to be located
just south of Comstock Road within the old Northshore Marina lot and an
adjacent parcel that currently contains a residential structure. The house is
located within the 100-year floodplain and is considered a hazard for flooding.
The sediment pool would require periodic maintenance in order to remove the
sediment build-up. Upland areas around the sediment pool would be set aside for
maintenance access and storage. The pool will serve the same function that the
lake has been providing by trapping sediment, but this will limit the area requiring
maintenance and increase accessibility.
Normal pool elevation would be dropped 2.5 feet to a normal pool elevation of
262 feet in order to provide additional flood storage without raising the dam and
impacting adjacent landowners. The proposed spillway structure is a notched
drop-chute spillway that would incorporate a 25-foot-wide weir at an elevation of
263'. In order to pass high flows, a 150-foot weir length would be constructed at
an elevation of 265.9'. To minimize impacts to the dam, the structure will
protrude into the lake. The hardened channel below the weir would slope from an
invert elevation of 261' down to 256', where it would then tie into the existing
channel below the dam. In addition, several 2" water-quality drawdown holes
using orifice plates at an elevation of 262' will be included in the spillway. These
holes will reduce clogging and will pass the daily flow in addition to any
floodwaters stored between 262' and 263'. Flood storage capacity would be
Northshore do Brentwood Today lakes
4041401 Permit Application Narrative
Page 3of15
increased by 1.5 vertical feet with an additional 1-foot drawdown for water
quality improvement purposes.
Approximately 1.5 acres of the lake would be dredged to remove much of the
depositional sediment that has accumulated over the 50+-year life of the lake.
Using existing bathymetry as a guide, the dredging would occur in the upper
portions of the lake and around parts of the lake perimeter. The dredging would
also be performed in order to keep the lake surface area approximately equal to
current conditions. Since some of the existing wetlands may be drained due to the
drop in water elevation, planting of created headwater wetland areas may occur to
enhance their development. An approximate 0.7-acre headwater wetland would
be created below the sediment pool to help filter out nutrients and contaminants
prior to reaching the lake. This headwater wetland will be planted with trees and
constructed such that shallow channels braid through the system. Small plunge
pools are proposed where existing point-source pipes and channels discharge
directly into the lake. These would provide some treatment for sediment and
contaminant runoff from the stormwater outfalls.
Brentwood Today Lake (Figure 3)
The Brentwood plan would provide primarily for spillway replacement and lake
bathymetry restoration. The existing spillway structure has been progressively
failing over a period of years and needs to be addressed relatively soon in order to
prevent a complete failure of the spillway (a failure of this magnitude may result
in an outflow that could adversely impact downstream lives and property in
addition to the aforementioned Beaman Lake reconstruction project). The
proposed structure would have a 100-foot weir length at an elevation of 245.2'
with a 20-foot notch cut down to 242'. The channel invert below the weir would
be 238', sloping down on a 1-percent grade to an energy-dissipating structure at
the confluence with the existing stream channel. No change in water level is
proposed for this lake since it would add only a minor amount of additional flood
storage.
Approximately 3 acres of lakebed would be dredged. A 0.4-acre sediment pool
would be created where an eastern tributary enters the lake. A plunge pool along
the western shoreline and a sediment pool below New Hope Church Road are also
proposed in this plan. Other than the minor wetland impact from the eastern
sediment pool, the wetlands on-site are to be preserved in order to provide water
quality and habitat benefits.
Alternatives Analysis
The attached technical memoranda describe the Concept Plans shown in Figures 2
through 3, along with the analysis used in the evaluation of these alternatives. In general,
three alternatives were evaluated for each lake:
¦ Dam safety and flood attenuation,
Nonlhslmre & Brentwood Today Lakes Page 4 of 15
4041401 Permit Appliration Narrative
¦ Water quality improvements, and
¦ A composite plan integrating dam safety and water quality (Recommended Plan).
The dam safety recommendations were integrated into all three alternative scenarios,
since exclusion of these recommendations was not practical due to public safety
concerns. Therefore, a "no action alternative" was not considered for permitting
purposes for this project.
The analysis, fully documented in the attached technical memoranda, resulted in the
recommendation of the plan described above. This plan included the required elements
for dam safety and flood attenuation, and incorporated both water quality elements and
public interests. The resulting project yields an increase in water quality efficiency of the
facilities, while satisfying to the greatest practical extent the needs and interests of the
adjacent landowners.
Project Impacts, Minimization, and Avoidance (Items 20, 21, 22)
The impacts of the proposed project on each type of jurisdictional area are presented in
Table 1 and discussed by site below. Along with each impact description is a discussion
of the minimization and avoidance performed at each site. Overall, impacts are mostly
limited to the original footprint of the lakes and spillways prior to the sedimentation and
infilling that has occurred over their 50+-year existence. Stream and wetland delineation
was performed in April-May 2004, and field-verified by Ms. Jennifer Burdette on July
13, 2004 (existing conditions are shown in Figures 4a, 4b, 5a, and 5b; proposed
conditions with impacts in Figures 6a, 6b, 7a, and 7b).
Table 1: Impact Summarv
Site
Number Lake Open
Water ac Forested Wetland
Impact ac Fringe
Wetlands ac Stream
Channel U.
1 Northshore 0.51 0.46 - 260
2 Northshore - - 0.03 -
3 Northshore 0.08 - - -
4 BrenMood Today - 0.07 - 80
5 Brenhvood Today 0.04 - - 50
Totals 0.63 0.53 0.03 390
Site 1 - Northshore Headwaters:
0.46 acres of riparian forested wetlands will be impacted in this area due to the
drop in the normal pool elevation of the lake (Figure 6a). This will eliminate the
hydrologic conditions necessary for the survival and propagation of the wetland
species currently present. In addition, over time the hydric soil characteristics of
this area will be eliminated and the area will likely revert to an upland riparian
system. 0.51 acres of pond will be converted to wetland due to the reduction in
water levels. This area will be planted with riparian wetland vegetation in order
to enhance the water quality benefits of the project and replace the habitat lost in
the draining of the current wetland areas. Approximately 0.18 acres of the 0.46
Northshore do Brennvood Today Lakes
4041401 Permit Application Narrative
Page 5 of 15
acres of wetlands will also be excavated to allow for the construction of a 0.8 acre
sediment pool or forebay within the original footprint of the lake. This forebay
will be used to minimize the amount of maintenance required in the future and
limit this activity to an easily accessible area. The forebay construction will
impact an additional 260 linear feet of perennial stream channel that is currently
inundated by the lake.
Avoidance of this impact was not practical due to the heavy historical and current
sediment load that has led to the conditions described above. An off-line
sediment pool or forebay was considered for this location in order to avoid
impacting the current stream channel and wetlands. This would have divided the
forebay into two sections on either side of the stream and greatly reduced the
volume of water controlled. In addition, normal base flows would have been
passed by the stream without contact with the sediment pools. Since the entire
lake is currently acting as a sediment pool for the upstream drainage, it was
determined that an in-line forebay was the most practical option.
Draining of the current wetland areas was examined to determine if there were
options to avoid this impact. However, since flood control is a primary concern
below the dam, the water level has been decreased in the Recommended Plan to
provide additional flood storage and spillway capacity, which brings the dam's
spillway capacity into compliance with the NC Dam Safety Act. Since the flood
control storage drop of 1.5 feet is necessary and would drain the wetlands at the
site, it was determined that an additional 1 foot of water drop would be beneficial
for water quality purposes and would not cause additional impacts to the
wetlands. Alternative flood control strategies, such as raising the existing dam
elevation, were considered but found to not be practical due to the potential
impacts on adjacent landowners.
Site 2 - Northshore Fringe Wetlands
0.03 acres of current fringe wetlands are located around Northshore Lake as
shown in Figures 4a and 4b. These wetlands have formed in the flatter portions of
the lake margin where water is shallow enough to allow colonization by
hydrophytic plants. Lowering the water level will impact all of these wetlands.
The dredging of the lake will maintain the current lake margins by creating a
shallow shelf along the edge of the lake. Fringe wetlands are likely to reform in
areas that supply suitable depth.
As stated above, avoidance of the water level decrease was examined but deemed
not practical due to flood control and spillway capacity issues necessary to
comply with the NC Dam Safety Act. Therefore, the impacts to the fringe
wetlands are necessary. Minimization of these impacts is being achieved through
the dredging of adjacent shallow waters to maintain the current lake banks and
create shelves along the shore. This will allow for the natural reestablishment of
fringe wetlands in suitable locations around the perimeter of the lake.
Northshore & Brentwood Today lakes
4041401 Permit Application Narrative
Site 3 - Northshore Dam and Spillway
Page 6 of 15
The construction of the Northshore spillway device, shown in Figure 6b, will
impact approximately 0.08 acres of open waters. No additional stream channel
will be impacted by the rehabilitation of the existing spillway downstream of the
dam. This stream channel is currently concrete and rock lined. This material will
be removed and replaced with proper materials. During construction, the stream
will be diverted around the current channel through pipes, preferably via gravity
flow.
Avoidance of this impact was deemed impractical due to the high flood hazard
conditions, the current state of the spillway, and lack of compliance with the NC
Dam Safety Act. The enlarged weir will remove some open water, but is
necessary to control the flows entering the spillway and reduce downstream
velocities and flooding potential. The current spillway is cracked and a portion of
the base flow is bypassing the spillway through voids underneath. This would
eventually lead to the failure of the spillway and degradation of the downstream
channel. The spillway length has been limited to not cause additional impacts to
the stream channel. The leveling of the dam will not impact the stream or open
water.
Site 4 - Brentwood Today Eastern Tributarv
Although sediment is being controlled along the main stem lakes and stream
through the sediment pool on Northshore Lake, there is a significant amount of
the overall watershed (31%) that enters Brentwood Today Lake through an
eastern tributary that is piped under the Mini-City area along Capital Boulevard.
The sediment load in this tributary has created headwater wetlands similar to
those at the upper end of both lakes. In order to reduce this sediment load and
minimize further filling of the Brentwood Today Lake, a sediment pool is
proposed on this tributary. Construction of this pool will impact 0.07 acres of this
wetland area. The remaining wetland and the wetlands at the upper end of the
lake will not be impacted. In addition, 80 feet of perennial stream channel of the
eastern tributary will be impacted by construction of the sediment pool (Figure
7b).
Avoidance of this impact was considered, but it was not deemed practical due to
the sediment load currently produced from the watershed to the east of Brentwood
Today. As discussed above, an offline forebay would not control base flow
sediment load and would be greatly reduced in size. In addition, it would likely
involve additional taking of properties.
Site - Brentwood Today Dam and Spillway
The 50 feet of remaining spillway at the Brentwood Today Lake is progressively
collapsing and the banks of the stream channel are sloughing in. The original
spillway length below the dam was approximately 200 feet. The proposed
spillway length is 100 feet, which yields an additional impact of 50 linear feet of
Nonluhore & Brentwood Today Lakes
4041401 Permit Application Narrative
Page 7 of 15
perennial stream channel when compared to current conditions, but is within the
original footprint of the 200' spillway. The current conditions of this stream
channel, and the impending failure of the remaining 50 feet of the spillway,
prevent any other alternative solution besides draining the lake. The inlet
structure will impact an additional 0.04 acres of open waters.
Avoidance of the spillway improvements was unavoidable due to the state of the
current structure. Of the original 200 foot spillway, only 50 feet remain (and
sections are continuing to collapse). The proposed length of the spillway is
enough to pass the required flows (based on Dam Safety Act requirements) and
tie into the existing stream channel while reducing velocities of the outflow so as
to minimize potential for downstream degradation.
Mitigation
The original concept for compensatory mitigation for this project was to use the enhanced
wetlands associated with the Northshore Lake (Figures 6a and 6b) to offset the
unavoidable wetland losses. In an October 5, 2004 pre-application meeting with the
USACE, it was determined that these wetlands could not be used as compensatory
mitigation since they are a component of a stormwater facility. This was concurred by
the EPA in email correspondence on February 7, 2005. It was agreed in the pre-
application meeting with the USACE that a proposal would be considered to not require
mitigation for impacts if functional replacement could be proven for the project. DWQ
401 Certification Unit staff tentatively agreed to a similar approach in an October 22,
2004 pre-application meeting. Therefore, the following mitigation section is designed to
justify the waving of compensatory mitigation for the proposed impacts due to the
functional replacement of the project components.
Wetland Functions
The impacted wetlands are discussed below by category of wetland functions as
described in the "Guidance for Rating the Values of Wetlands in North Carolina"
published by NCDENR.
Dater Stora.ee
The current wetland areas consist of bars of sediment transported downstream and
deposited at the inlet of the lakes. Little microtopographic relief is present in
these wetlands and therefore their water storage capacity during flood events is
low. As these wetlands have formed above the normal pool elevation of the lakes,
they have actually decreased the amount of flood storage provided by the
freeboard of the lakes. The increase in flood storage capacity created by the drop
in water level of Northshore Lake will greatly increase flood storage capacity of
the entire system and therefore offset any loss of flood storage retention in the
wetland areas.
Nortluhore & Brentwood Today Lakes
4041401 Permit Application Narrative
BanUShoreline Stabilization
Page 8of15
The current wetlands consist of fine silts and sands deposited in the upper end of
the lakes. These areas are constantly shifting and provide little stabilization of the
stream banks. Vegetation in much of these areas is limited to herbaceous species
such as Jewelweed (Impatiens capensis) that provide little stabilization.
Reduction of the water level in Northshore, along with the dredging of sediments
in both lakes, will remove most of these sediments. The creation of the sediment
pools prior to these wetland areas will help to reduce the erosive velocities and
scour potential of the streams and therefore will not decrease the bank
stabilization of the system. Currently, the stream channels immediately upstream
of the open water are pooled, channelized, and relatively incised. The channel
below the Brentwood Today dam is currently caving in and causing additional
water quality problems. Overall, the project will reduce downstream erosion
potential by controlling flooding and reducing velocities downstream of the
spillways. This reduction in erosion and stabilization of the currently eroding
banks adjacent to the spillway will help mitigate the minor stream impacts
associated with the project. The current conditions of the streams, specifically the
stream below Brentwood Today, would more than mitigate for the loss of this
function.
Pollutant Removal
The current wetlands do provide some pollutant removal for the incoming flows.
However, as described in the following text and supported in the attached
technical memoranda, pollutant removal efficiencies will be increased throughout
the watershed as a result of this project. This was one of the primary purposes of
this project.
Examination of the New Hope Tributary (including Northshore and Brentwood
Today Lakes) as the system of treatment facilities for the entire watershed
provides a comprehensive assessment of water quality. Table 2 integrates the
combined loadings from all five sub-watersheds studied (attached as Technical
Memorandum No. 4) and the trapping capacity of both lakes to yield a composite
load and overall removal efficiency from the system. These results are presented
in the last three columns of Table 2. The system is operating in the mid-range of
the removal efficiency for wet ponds, based on the initial assumptions of poor
removal capacity for the individual lakes. However, the main function of this
system simply operates to detain pollutants and does not facilitate the expedition
of these pollutants entirely out of the system. Nitrogen, phosphorus, and TSS
would be available for reintroduction into the system's downstream conveyance.
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Page 10 of 15
inundated most of the time. Based on interviews with local residents, fish
populations in both lakes have seriously declined in the last several decades. The
aquatic benches created by the dredging operations will add aquatic habitat by
providing shallow water refuge adjacent to deeper water habitat. The construction
of the spillways will not change the current impediments to fish passage. The
overall project will improve the quality of the aquatic habitat in both the lakes.
Recreation and Education
Recreation opportunities, which were originally quite high for these lakes, have
drastically decreased over the last several decades. Fishing has declined due to
the decrease in fish populations associated with the poor water quality and
sedimentation. Boating opportunities have also declined as significant portions of
these lakes have become inaccessible by watercraft. Several docks are currently
surrounded by wetlands or water less than 1 foot deep. The project will increase
both these functions to a great extent. Fish habitat will be increased, and over
time fishing opportunities should likewise increase. Boat access will be enhanced
through the dredging of the lakes. While some areas without current open water
access will not change (such as the upper portion of Brentwood Today),
landowners with access to open water will have that access enhanced through the
dredging of channels and deepening of the lakes.
Stream Mitigation
Stream impacts associated with this project are limited to 390 linear feet of
perennial stream. Current stream channel degradation along the old spillway of
Brentwood Today Lake will be repaired during the construction of the spillway,
and downstream impacts from sedimentation and erosive velocities will be
reduced by the proposed enhancements and rehabilitation. Since the stream
channels along the spillways of these lakes have already been impacted, only
additional stream channel impacts have been included in these calculations. Any
channel impacts occurring at the upper reaches of each lake are impacting open
water that falls within the streambanks - these channels are not functioning as
streams but as open water conveyances. Some grade control points may be
established in the exposed stream channels to prevent head cutting as needed.
Therefore, no stream mitigation is being proposed for this project. The overall
watershed and water quality improvements associated with this project provide
sufficient mitigation for the minor amounts of stream impacts.
Based on the overall assessment of the functions described above, each wetland
function is at minimum replaced and, more frequently, enhanced by the project.
Stream impacts and enhancements are largely offset by the primary goal of water
quality improvements and the rehabilitation of the dams. The overall goals of
flood control and water quality, along with the current severely degraded state of
these lakes, provides mitigation for these functions through an alternative delivery
process rather than traditional compensatory mitigation. It is therefore proposed
that no formal compensatory mitigation be required for the impacts associated
with this project.
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Neuse Buffer Impacts and Mitigation Requirements
Page II (/f 15
Figures 6a, 6b, 7a, and 7b present the current riparian buffers within the project area
under jurisdiction of the Neuse River Riparian Buffer Rules. The proposed plan will
impact 1.95 acres of the total 12 acres of buffers currently surrounding the lakes. These
impacts stem primarily from spillway improvements and sediment pool construction.
The impacts related to the rehabilitation of the dams and spillways are exempt under the
current rules. Since the dredging operation will retain the current lake limits by creating
benches along the shores, no permanent loss of riparian buffers are associated with this
activity. The construction of the sediment pools will require impacts to 0.84 acres of
riparian buffers. These impacts do not create new impervious surfaces.
Protected Species
Plants and animals classified as Endangered or Threatened by the U.S. Fish and Wildlife
Service (USFWS) are protected under provisions of Section 7 and Section 9 of the
Endangered Species Act of 1973, as amended. Table 9 presents USFWS list of federally
protected species for Wake County, North Carolina as of February 25, 2003.
Table 3: Federal Listed Protected Species for Wake Countv. NC
Scientific Name Common Name Federal Status
Haliaeetus leucocephalus Bald eagle Threatened-Proposed
for Delistin
Picoides borealis Red-cockaded woodpecker (RCW) Endangered
Alasmidonta heterodon Dwarf wed emussel Endangered
Rhus michauxii Michaux's sumac Endangered
Limited potential habitat exists on-site for each species (Bald eagle - open water; RCW -
mature pines; Dwarf wedgemussel - perennial streams; Michaux's sumac - regularly
maintained edge habitat). Prior to construction, surveys will be performed for each
species as requested by the permitting agencies.
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Table 2: Comparative Loading Analvsis
Page 9 of 15
Loadings to Total Loadings to
Trapped Load from
Loadings out of Overall
Constituent Beaman Brentwood &
the System
Brentwood Removal
Lake' Northshore Efficienc
Total Nitrogen 3,872 13,320 4,124 9,196 31%
Total Phosphorus 1,215 1,400 787 613 56%
TSS 284,712 285,050 226,648 58,402 80%
Fecal Coliform N/A 4,540 850 3,690 19%
NOTES: Loadings are presented in Ibs/year except for fecal coliform, which are presented in colony forming units x
101iyear: '- Data from Beaman Lake Embankment Rehabilitation report.
The initial assessment of total nitrogen removed by Northshore and Brentwood
appears to meet the 30 percent reduction requirement in nitrogen specified in the
Neuse River Rules. However, the City of Raleigh's Stormwater Management
Design Manual requires that the nitrogen load from new development not exceed
3.6 lbs/acre/year. This equates to approximately 2,700 lbs/year, which would
theoretically be the target loading out of Brentwood Lake if the two watersheds
were not already mostly built-out. This is a much smaller loading as compared to
the present loading of approximately 9,200 lbs/year out of Brentwood Today.
While the 2,700 lbs/year may not be a reasonable goal, it still emphasizes the need
for maximizing nitrogen control where possible.
Iildlife Habitat
The current wetlands are relatively small and provide little wildlife habitat. The
vegetation primarily consists of herbaceous species, with some younger saplings,
shrubs, and trees. The surrounding land use is almost completely built out and
provides little refuge for populations of wildlife. Potential cover is adequate only
in spotty areas, and is periodically cleared out by adjacent landowners. Mast
producing trees and other food sources are limited by this disturbance. The
project will remove some of the thin riparian buffer along the streams and lakes in
the area of the sediment pools. This will be mitigated by the replacement of
similar vegetation types and cover in the enhanced wetlands created by the
exposure of additional land surface when the Northshore Lake level is dropped.
Additional open water created by the dredging operations, along with the
establishment of littoral shelves and benches around the perimeter of Northshore
Lake will increase waterfowl habitat.
Aquatic Life
Currently, the aquatic habitat of the two lakes and connecting streams is in poor
condition. As described above, the lakes have gradually filled in with sediment
and therefore removed most of the deepwater habitat in these systems.
Approximately 30% of Northshore Lake and 50% of Brentwood Today are less
than 1 foot deep. This has created conditions that promote the growth of algae
and invasive aquatic plants that are currently choking the system. The dredging
of the lakes and control of the sediment load coming downstream will greatly
enhance the aquatic habitat of the lakes. The lowering of the Northshore water
level will allow the stream below Comstock Road to flow rather than be
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Photographs
{ %j

Page 12 of 15
Upstream end of Northshore Lake, looking upstream near Comstock Road
x?
Upper end of Northshore Lake
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Page 13 of 15
Northshore Lake, looking upstream from the dam

.
+i+
A
Top of Northshore Lake spillway
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Page 14 of 15

Brentwood Today dam spillway, looking downstream from the top of the spillway (as of
September 2004)
Brentwood Today Lake, looking upstream from the dam
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Page 15 of 15
Post-storm destruction below Brentwood Today spillway due to bank erosion and sloughing
(April 2004, along the eastern streambank and -20' downstream of existing spillway)
Approximate former location of Brentwood Today spillway, now -150 feet downstream of
the progressively collapsing end of the spillway seen above

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Jamison, John R.
From: [e-mail]
Sent: Monday, February 07, 2005 3:00 PM
To: May, Philip
Cc: [e-mail]
Subject: RE: Forebay Issues
Phil,
Just wanted to send you a quick reply to your forebay question before I head out on work
travel. It is my opinion that the forebays will not be an issue if the permit decision is
made to convert these ponds to stormwater treatment systems and appropriate mitigation is
provided for this loss of "waters" since they will no longer be jurisdictional waters of
the US. I also spoke to EPA's regional stormwater expert and she concurred with this. We
would caution that the forebays should not be constructed to a depth as to allow them to
become anoxic and/or to thermally stratify. It appears this is not the case with your
design which indicates forebays will be constructed 2 to 4 feet in depth. Most literature
recommends an average depth of wet ponds to be in the range of 3 to 9 feet. If you are
wanting to go deeper than that we would like to further discuss this with you. We would
recommend that you might want to make your forebays a little deeper than you are proposing
to allow for some accumulation of coarse material between scheduled maintenance. This
would help prevent resuspension of particulates during larger events.
One concern I did have when I reviewed your website is that it appears you are proposing
wetlands between the forebay and the larger pond to be used as mitigation for project
impacts. This is something we would want to discuss with you and Jennifer since it is our
position that mitigation credit can not be given for an area that is not jurisdictional
which would apply to these ponds if they are converted to storm water treatment systems.
Shallow wetland shelves are an important component of a good pond treatment system so we
would encourage their construction but can not recommend they be used to provide
mitigation credit.
Let me know if I can be of any more assistance
getting back to you on the forebay issue.
Once again, sorry for the delay in
Becky Fox
Wetland Regulatory Section
USEPA
Phone: [phone]
Email: [e-mail]
"May, Philip" <[e-mail]> wrote on 01/24/2005 03:08:59 PM:
> Thanks Becky - I understand how your schedule must be - especially
around the
> holidays.
> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]]
> Sent: Monday, January 24, 2005 3:00 PM
> To: May, Philip
> Subject: RE: Forebay Issues
> Thanks for the reminder Phil. Things have been crazy since we
communicated
> in Nov and I have not been to Raleigh since then but this project has
been
> floating about in the back recesses of my mind and I knew that I owed
you
> some comments. I will try to get back with you sometime either this
week or
> early next week.
1
> Becky Fox
> Wetland Regulatory Section
> USEPA
> Phone: [phone]
> Email: [e-mail]
> "May, Philip"
> <Phil.May@hdrinc. To: Rebecca
> Fox/R4/USEPA/US@EPA
> com> cc:
> Subject: RE: Forebay
Issues
> 01/24/2005 02:33
> PM
> Becky
> I just wanted to let you know that the City is asking us to prepare
and
> submit our permit prior to our last meeting with the public. If you
have any
> comments on the forebay issue in the next couple of weeks, please let
me
> know. Otherwise, we should be submitting the IP in mid-February and
will
> respond to any comments during the review of the permit.
> Thanks
> Phil
> -----Original Message-----
> From: May, Philip
> Sent: Monday, November 29, 2004 11:32 AM
> To: '[e-mail]'
> Subject: RE: Forebay Issues
> Becky,
> The forebays are planned for the upstream portions of the ponds, which
have
> filled in over the last couple of decades. There are existing
wetlands in
> these areas, however the planned change in water level (to alleviate
flooding
> below the dam by increasing flood storage) would likely drain these
areas.
> We have a web site for the project - www.raleighlakes.com - this has a
> summary of the information provided in a couple of public meetings.
The web
> site is probably the easiest way to get you information - it has a
couple of
2
> powerpoint presentations used in the first community meetings (click
on "more
> information" at each of the community meetings). If you need any more
> information please let me know.
> At this point we have come up with three alternative plans for each of
the
> two lakes and proposed one of each as the recommended plan, but we
would like
> to incorporate all the regulatory input we can get prior to a last
public
> meeting on the final recommended plan. I would like to know the
feasibility
> of using forebays on the project prior to that. I doubt this meeting
will
> happen before January.
> Please call me at your convenience if you have any questions or need
me to
> send you more information.
> Thanks
> Phil
> -----original Message-----
> From: [e-mail] [mailto:[e-mail]]
> Sent: Monday, November 29, 2004 10:05 AM
> To: May, Philip
> Subject: Re: Forebay Issues
> Phil,
> Will the forebays be constructed in the upstream portion of the ponds
to be
> rehabilitated or will the forebays be constructed upstream of the
current
> dams? If you could send me some info that would be great. You could
send
> smaller files (without pictures and maps electronically) or mail
larger files
> to:
> 1349 Firefly Road
> Whittier, NC 28789
> After reviewing the info I will contact you about either meeting or
phone
> conference to further discuss the projects. What is your time frame?
> Thanks,
> Becky Fox
> Wetland Regulatory Section
> USEPA
> Phone: [phone]
> Email: [e-mail]
> "May, Philip"
> <Phil.May@hdrinc. To: Rebecca
> Fox/R4/USEPA/US@EPA
> com> cc:
> Subject: Forebay
3
Issues
> 11/29/2004 09:49
> AM
> Becky,
> On John Dorney's advice, I am contacting you in regard to the use of
forebays
> on a project involving the rehabilitation of a couple of dams on small
ponds
> in the City of Raleigh. The City is studying these lakes with the
intention
> of repairing the dams or spillways, and adjusting the water levels
(with some
> dredging) to provide additional flood storage and water quality
improvements.
> As a part of the plan we are developing, we have included the use of
deep
> pools or forebays at the upper end of these lakes. I was hesitant to
include
> this and warned our engineers and the City that in-line forebays could
be an
> issues, but the Corps (Jennifer Burdette) said that in conversations
with you
> the forebay issue was not really a problem since the entire lake would
serve
> a stormwater function. John Dorney's take on this is different and he
> therefore recommended we discuss this directly with you.
> I would be happy to send you some information to review. We would
also like
> to meet with you when it is convenient to discuss the project. Do you
have
> any time on upcoming trips to Raleigh to meet?
> Thanks
> Phil
> Philip May
> HDR Engineering, Inc. of the Carolinas
> 3733 National Drive, Suite 207
> Raleigh, NC 27612
> [phone]
> [e-mail]
4
TECHNICAL MEMORANDUM NO. 4
Water Quality Evaluation of Conceptual Plans
NORTHSHORE LAKE AND
BRENTWOOD TODAY LAKE
DAM REHABILITATION PROJECTS
CITY OF RALEIGH, NORTH CAROLINA
February 22, 2005
Prepared By:
a
HDREnglneerrng, Inc. of the Carolinas
HDR Project No. 10913-9154
TABLE OF CONTENTS
SECTION
PAGE
1.0 INTRODUCTION ............................................................................................................................1
1.1 Overall Project Description ..................................................................................................1
1.2 Water Quality Component ...................................................................................................1
1.3 Preliminary Water Quality Assessment Methodology ........................................................2
2.0 WATER QUALITY EVALUATION AND MODELING ...........................................................3
2.1 Purpose .................................................................................................................................3
2.2 Model Selection ...................................................................................................................3
3.0 MODEL DEVELOPMENT ............................................................................................................ 5
3.1 Future Land Use Analysis .................................................................................................... 5
3.2 Watershed Delineation ......................................................................................................... 5
3.3 Hydrologic Parameters ......................................................................................................... 6
3.4 Water Quality Parameters .................................................................................................... 7
3.5 Device Parameters ............................................................................................................... 8
3.6 Meteorological Data ............................................................................................................. 8
3.7 Calibration ............................................................................................................................ 9
4.0 MODEL EXECUTION ....................................................................................................................9
4.1 Alternatives Development ...................................................................................................9
4.2 Results and Findings ..........................................................................................................13
5.0 MODEL EVALUATION ...............................................................................................................18
5.1 Continuity Errors ................................................................................................................18
5.2 Sensitivity Analysis ............................................................................................................18
6.0 CONCLUSION AND DISCUSSION ...........................................................................................19
7.0 REFERENCES ...............................................................................................................................21
LIST OF TABLES
3-1 Event Mean Concentrations (EMC) for Selected Pollutants ..............................................................8
4-1 Comparison of Pollutant Loadings from the Preliminary Assessment and the Model .................... 13
4-2 Overall TSS Removal Efficiency (%) .............................................................................................. 14
4-3 Overall TPP Removal Efficiency (%) .............................................................................................. 15
4-4 Overall TKN Removal Efficiency (%) ............................................................................................. 16
4-5 TSS Loading (lbs) Discharge out of Brentwood Today Lake .......................................................... 17
4-6 TP Loading (lbs) Discharged out of Brentwood Today Lake .......................................................... 17
4-7 TKN Loading (lbs) Discharged out of Brentwood Today Lake ....................................................... 17
LIST OF FIGURES
1-1 Project Site Location ...........................................................................................................................2
4-1 Graphical Depictions of the Modeled Networks for the Alternatives ..............................................12
4-2 Removal Efficiency (%) for Discrete Particles .................................................................................15
Water Quality Evaluation i February 2005
of Conceptual Plans
SECTION 1.0 - INTRODUCTION
1.1 Overall Project Description
There are a series of four lakes along the New Hope tributary to Marsh and Crabtree Creeks: an
unnamed lake, Northshore, Brentwood Today, and Beaman. The unnamed lake and Beaman are
presently not included within the scope of this Project. The dam at Beaman Lake was breached
several years ago and is currently under reconstruction, restoring the dam embankment and
installing features to improve water quality.
This Project includes Northshore and Brentwood Today Lakes, which are located in the City of
Raleigh (City) near New Hope Church Road and west of U.S. 1 as shown in Figure 1-1. The
dams at both Lakes were identified as small, high hazard dams in the Titan Atlantic Report dated
July 20, 2004. Furthermore, the spillways at both Lakes have been a concern for over 20 years.
The dams have been overtopped several times in recent years, causing flooding in the
surrounding residential area. There is a concern that New Hope Church Road, located just
downstream of Northshore Dam, may wash out during an overtopping event.
The purpose of this project is to evaluate both Northshore and Brentwood Today Lakes for dam
safety concerns and water quality improvements. Three different aspects will be evaluated:
.e Dam safety and flood attenuation,
.e Water quality improvements, and
A composite plan integrating dam safety and water quality.
The purpose of this Technical Memorandum (TM) is to provide an evaluation of water quality
for these three alternatives. Additionally, a discussion of the results of this evaluation along with
baseline conditions derived in previous assessments and the differing aspects of the two
approaches will be presented.
1.2 Water Quality Component
Northshore and Brentwood Today Lakes are classified as C Nutrient Sensitive Waters (NSW) by
the North Carolina Division of Water Quality (NCDWQ). Both Lakes have not yet been rated
for their level of support for this designated use. NSW are less likely to assimilate additional
loadings of nutrients, primarily nitrogen and phosphorus, without detrimental effects on the
water quality. The lake's inclusion as NSW is likely due to their watershed being part of the
Lower Neuse River Basin.
Water Quality Evaluation February 2005
of Conceptual Plats
I I _.
1
Mini City
(Development)
?I
Northshore
L -s New
190
.00
Brentwood Today h4?ch'lo -
a --
7 -
L
T
1

?I
I
N Legend Figure 1.1
-Water Bodies
-- -- Road Project Site Locatio
A Wake County CITY OF RALEIGH
Hydrology
City of Raleigh
0 1,000 2,000 January 2005 ]? H?+en9inE
Feet Sub-watershed Boundaries ultheCato

Inc.
Northshore and Brentwood Today Lakes have been significantly impacted in the last 20 years.
During this time, the watershed has seen significant commercial and high density residential
development. The most notable commercial development was the construction of "Mini City"
off Capital Boulevard. With this development has come the disturbance of land and an increase
in impervious area throughout the watershed. The increase in impervious surface increases peak
flows during storm events may have resulted in erosion of unstable stream banks. In addition,
stormwater has transported sediment to these Lakes. This is evident by the unconsolidated soil
deposition found in the mouths of the contributing streams to Northshore and Brentwood Today
Lakes. It is also likely that sediment is carrying a host of urban pollutants to these Lakes, such as
nutrients, metals, organic matter, and fecal coliform.
Eutrophication is also apparent in both Northshore and Brentwood Today Lakes. The abundance
of sediments and solids in stormwater, likely transporting nutrients, as well as dissolved nutrients
found in fertilizers typically used in residential areas have also been conveyed to these Lakes.
Their presence in excess quantity has lead to the excessive growth of phytoplankton or floating
algae that is currently seen in the two Lakes. As the excessive algal biomass dies, it consumes
the bulk of dissolved oxygen that supports life Other contributing sources to the eutrophication
include the waterfowl nesting at the Lakes, domestic pet waste, and possible failing sanitary
sewer lines or sewer overflows.
Bacterial contamination of the Northshore and Brentwood Today Lakes is a prominent concern
as these Lakes are sources of recreation for the adjacent property owners. The Lakes are Class C
and therefore should support the designated uses of secondary contact recreation such as boating
and wading. Visual inspection of the area indicates that some sources of bacterial contamination
(i.e., waterfowl excreta) have direct contact with the Lakes. These Lakes are typical of the urban
setting, in that they likely exhibit fecal coliform levels that do not support the C waters
classification.
1.3 Preliminary Water Quality Assessment Methodology
A preliminary water quality assessment was performed early in the project and documented in
Technical Memorandum #2 Water Quality Assessment (TM #2). The objective of that water
quality assessment was to evaluate the level and location of pollutant stress being delivered to
these Lakes. That assessment assisted in determining suitable design elements and their location
as well as providing a preliminary baseline for design efficiency. The methodology employed
for the analysis utilized literature values of pollutant export coefficients and geographic land use
data to generate loadings for specific sub-watersheds. That cursory view of watershed conditions
was beneficial in determining a more detailed approach to be used in the final water quality
evaluation of the Project alternatives.
Water Quality Evaluation L February 2005
of Conceptual Plans
SECTION 2.0 - WATER QUALITY EVALUATION AND MODELING
2.1 Purpose
The purpose of this effort and TM are to provide an evaluation of several alternatives with
respect to the improvement of water quality downstream and within the Lakes' system. It is
difficult to translate water quality goals (i.e., concentration and removal efficiency) into tangible
water quality benefits due to the high variability of natural processes and the existence of
unaccountable interactions. However, assuming that this variability is inherent and global, a
relative evaluation of alternatives with similar base conditions and processes will yield a similar
relative response in water quality benefit. An evaluation performed through modeling and sound
interpretation of results will provide this relative assessment.
Water quality models can be used for the prediction of loading, transport, and control of
pollutants. The application of a water quality model will expand upon the empirical effort
accomplished in the TM #2 by incorporating representative data with the simulation of the
existing physical processes. The use of a water quality model will further the assessment in the
following ways:
¦ Provide pollutant loading based on studied pollutant development and hydrologic interaction.
¦ Routing and transport of flow and pollutants through continuous water and mass balance.
¦ Simulation of physical pollutant removal processes and their efficiency over varied
flow/volume regimes.
2.2 Model Selection
The type of water quality model required to fulfill the aforementioned objectives lies within the
range of mid-level models. These models compromise the empiricism of the simple methods
and the complexity of detailed models driven by parameter intensive, mechanistic processes
(EPA, 1999). When fully calibrated and inputed with site-specific parameters they can provide
an appropriate means of prediction. Despite limitations on data availability, these models still
provide decision makers the ability to select watershed-level planning solutions based on relative
comparisons. P8-Urban Catchment Model (P8-UCM), developed for IEP, Inc and the
Narragansett Bay Project by William W. Walker, Jr., Ph.D, was selected for this application
based on these needs. The relative ease of parameter estimation and input and HDR's familiarity
Water Quality Evaluation 3 February 2005
of Conceptual Plans
of the model were factors in its selection. Additional strengths of the model for use in this
Project are listed below (EPA, 1992):
¦ Developed and calibrated for use within small, urban watersheds.
¦ Distributed with particle and water quality pollutant distribution data calibrated against
Nationwide Urban Runoff Program (NURP) data.
¦ Simulation of particle accumulation, decay, and wash-off dynamics.
¦ Sources can be characterized as single, continuous, or diffuse release.
¦ Continuous and storm event simulation.
¦ Provides for the inclusion of several structural Best Management Practices (BMPs): wetland,
detention ponds (dry, wet, and extended), infiltration basins, and swales/buffers.
¦ Hydrologic and water quality output can be evaluated at discrete model components.
¦ Relative evaluation of pollutant loadings, outflow concentrations, and BMP removal
efficiencies.
P8-UCM like many other urban runoff models has some limitations. The following is a brief
listing of limitations of this model (EPA, 1992):
¦ Lack of site specific calibration data limits the model in absolute prediction of pollutants
loads and concentrations.
¦ Primary pollutant removal process is sedimentation and filtration.
¦ Does not simulate in-stream transport and transformation processes for pollutants.
¦ Watershed lag is not simulated.
However, P8-UCM can be a scalable model, in the sense that many of these limitations can be
overcome with site-specific water quality data and representation of physical, chemical, and
biological processes through alternative parameterization.
Water Quality Evaluation 4 February 2005
of Conceptual Plans
SECTION 3.0 - MODEL DEVELOPMENT
3.1 Future Land Use Analysis
A future build-out analysis was performed by Watershed Concepts for the entire Marsh Creek
Basin as part of a hydrologic model. Field inspections of the Northshore and Brentwood Today
Lakes watersheds suggest that current land use conditions are near, if not at, future build-out
conditions. Performing another future build-out analysis with the same base data would yield
similar results. Better value of this analysis would be to evaluate the base data against
orthophotography and field inspections performed while collecting storm sewer inventory. It is
likely that due to the breadth of that previous future build-out analysis and the intent of its end
product, the data was not site checked entirely. With the limited focus of this project the existing
land use and future land use conditions can be individually verified. This is important in
determining hydrologic and water quality parameters for the water quality modeling. The
findings of this evaluation show that the current open space was under estimated by 50 acres.
Much of the land was either characterized as medium residential or industrial. Future build-out
analysis of the open space portion would likely result in some additional commercial land use
but remain mostly open space, as the identified parcels are small and isolated. Due to the small
percentage of mischaracterized land (approximately 6 percent of total watershed area) and its
distribution across the watershed, it is likely this difference will have little effect on
parameterization for this evaluation.
3.2 Watershed Delineation
Watershed delineations were first performed in TM #2 for the purposing of identifying
magnitude and source location of pollutant loads into the Lakes. These same delineations proved
to be sufficient for application in the water quality model and this evaluation. The delineations
were generated using a variety of data detailed below:
¦ City of Raleigh topographic and planimetric CAD data (2000)
¦ NCGIA/DWQ Hydrography (1998)
¦ HDR Storm Sewer Inventory (2004)
P8-UCM emphasizes the location of incoming flows for the proper mixing of flows and
concentrations. Watershed delineations were created to accurately represent the appropriate
routing of flows through existing and proposed water quality controls (sediment pools, wetlands,
Water Quality Evaluation 5 February 2005
of Conceptual Plaits
and ponds). The Northshore Lake drainage was delineated into three sub-watersheds called
Upper, Middle, and Lower. The Upper sub-watershed includes the area where the generated
runoff would pass through the smaller unnamed pond south of Calvary Road. The Middle sub-
watershed includes the area where the generated runoff would enter Northshore Lake as a stream
at the mouth of the lake. The final sub-watershed called Lower includes areas draining directly to
the body of Northshore Lake. The Brentwood Today Lake follows the same logic. It is
delineated into two sub-watersheds called Main and Tributary. They represent the areas where
generated stormwater enter the head and body laterally of Brentwood Today Lake and as a side
tributary, respectively.
3.3 Hydrologic Parameters
P8-UCM estimates runoff from precipitation data and hydrologic parameters. The model
evaluates runoff from pervious and impervious areas separately. Runoff for the pervious areas is
computed using the SCS curve number method. These values are adjusted internally based on
antecedent moisture conditions (Haith and Shoemaker, 1987). Since, P8-UCM is mainly applied
in urban settings; this method proves to be a sufficient approach due to its simple
parameterization of pervious conditions that account for only a minor component of the total
urban runoff. The required parameters for pervious runoff generation are SCS curve numbers
representing "open space" land use and respective hydrologic soil groups (SCS, 1986).
Impervious runoff is computed from the difference of cumulative rainfall and depression storage.
Runoff initiates as cumulative rainfall depth exceeds a user-specified depression storage depth.
After this point, runoff equals rainfall intensity for the impervious fraction of the watershed. The
required parameters for impervious runoff generation include depression storage values and
impervious fractions. Depression storage values were obtained from literature values
categorized by land uses (Wright-McLaughin Engineers, 1969) and impervious fractions were
obtained from SCS curve number descriptions (SCS, 1986). The runoff from pervious and
impervious areas is combined and routed to the downstream device with no lag.
The future build-out land use data, described in more detail in Section 3.1 Future Land Use
Analysis, and NRCS digital soil surveys were used to create areas for parameterization. This
hydrologic data was input into P8-UCM for individual land uses within the watershed
delineations. This was done so that future application of the model could be calibrated for
pollutant event mean concentrations if desired. Depression storage and impervious fractions were
input wholly for their respective land use. Only curve numbers for pervious areas were
computed on a composite area average for their hydrologic soil group.
Water Quality Evaluation 6 February 2005
of Conceptual Plans
3.4 Water Quality Parameters
The generation of water quality pollutant loads and runoff concentrations for P8-UCM is based
on the dynamics of particle accumulation and wash-off principles as well as pollutant mass
distribution within those particles. The first component of the quality representation is the
parameterization of particle classes. P8-UCM allows for the distribution of five particle classes.
For each particle class, particle generation parameters are input for both impervious and pervious
segments of a watershed. Impervious input parameters include accumulation rates, decay rates,
wash-off exponents and coefficients, and street sweeping efficiency (when applicable).
Additionally, runoff concentrations can be provided in favor of accumulation and wash-off
dynamics. On the pervious portion of the watershed, particle generation is based on input
parameters of pollutant concentration for the individual particle classes. Particle removal
dynamics are quantified within this component of the P8-UCM model as well. Removal
dynamics are characterized for individual particle classes by settling velocity and filtration
efficiency through pervious mediums.
The second component of the water quality representation within P8-UCM provides for the
distribution of pollutants among the particle classes. Pollutant mass per particle class is the input
parameter. Since multiple pollutants can be modeled with a single particle distribution, scale
factors exist for calibration if desired.
P8-UCM includes several particle distribution data files that can be used for default parameters
when particle and pollutant mass data is not available. The majority of this default data was
calibrated to represent the results obtained in the Nationwide Urban Runoff Program (NURP).
The particle distribution file titled nurp50.par was used in this evaluation. The file contains five
particles classes that are based on calibration of runoff concentration and settling velocity
distributions representative of median sites (i.e., particle class P10 = Ioth percentile). Distribution
of the pollutant mass among particle classes is based upon results of direct runoff concentration,
settling column tests, and typical removal efficiencies of treatment devices (Walker, 1990). This
particle distribution file contains accumulation/wash-off parameters and settling velocities for
four non-dissolved particle classes. The fifth particle class was developed to simulate the non-
settling, dissolved particles. The file also contains mass distributions for a variety of urban
pollutants such as particulates, nutrients, heavy metals, and hydrocarbons. Attention will be
primarily focused on total suspended solids (TSS), total phosphorus (TP), and total Kjeldahl
nitrogen (TKN). Table 3-1 displays the calibrated event mean concentrations per median data
sites of NURP.
Water Quality Evaluation 7 February 2005
of Conceptual Plans
Table 3-1
Event Mean Concentrations (EMC) for Selected Pollutants
Total suspended solids 100.0
Total phosphorus 0.33
Total Kjeldahl nitrogen 1.5
3.5 Device Parameters
Devices provide for the hydraulic routing of runoff and areas for pollutant removal. P8-UCM
utilizes a variety of devices such as an infiltration basin, swale/buffer, flow splitter, and aquifer;
however, this assessment will only require the use of a detention pond, a general device, and a
pipe/manhole. The detention pond can be used as a device with a permanent pool and a normal
outlet that can be quantified by a single weir and/or collection of orifices. The required input
data for detention pond devices include surface area and volume quantities for permanent and
flood pool levels. The normal outlet that drains only the flood pool requires weir and orifice
dimensions and coefficients. Devices with more complex outlet configurations can be modeled
with the general device which requires a stage-surface area-discharge relationship for its volume
and outlet data. Both these devices also possess a particle removal scale factor. This value is
typically z 1 but can be adjusted higher or lower for the response of the device due to decreases
or increases in hydraulic residence time. The pipe/manhole device is useful for mixing two or
more incoming flows before being routed onto a removal device. Its only input parameter is a
time of concentration and the device provides for no pollutant removal. Pipe/manhole devices
can be used for delaying the hydrologic response of watersheds through the time of concentration
parameter. This approach is beneficial for the modeling of larger watersheds since the watershed
components route runoff with no lag.
3.6 Meteorological Data
Several meteorological parameters are required to balance hydrology for the watershed in P8-
UCM (i.e. precipitation, evapotranspiration, and percolation). Only precipitation and
evapotranspiration require meteorological data. Hydrologic events are driven by hourly
precipitation. Hourly rainfall data monitored at the Raleigh-Durham International Airport was
obtained from the National Climatic Data Center (NCDC) and used with the model. A SCS
Type II distribution (1-inch design storm precipitation file) is distributed with the model package
and also used in this effort. P8-UCM also calculates evapotranspiration using Hamon's Method
from monthly averages of vegetative cover, air temperatures, and hours of daylight (Hamon,
1961). Daylight hours and air temperatures were collected for the area from Summary of the Day
Water Quality Evaluation 8 February 2005
of Conceptual Plans
data also obtained from NCDC. Average monthly values for daylight and temperature were
calculated and inputted. Default data was used for vegetative cover. The total evapotranspiration
calculated by this approach resulted in 29.1 inches/year.
3.7 Calibration
P8-UCM provides for hydrologic and water quality calibration through the use of many
calibration factors and a calibration utility. However, the project watershed and the New Hope
Creek tributary do not have any United States Geological Survey (USGS) gauging stations or
any other confident streamflow monitoring data. A hydrologic and water quality calibration may
not be warranted at this time since the focus of this effort is a relative comparison of alternatives.
However, if the direction of the model is to be a tool for detailed design assessment, collection of
calibration data would be beneficial.
SECTION 4.0 - MODEL EXECUTION
4.1 Alternatives Development
As previously mentioned in Section 1.1 Overall Project Description, this TM will focus on the
water quality benefit gain or loss of the three alternatives: dam safety and flood attenuation,
water quality improvements, and a composite plan integrating the two. Several factors were
considered in the development of these alternatives. Technical Memorandum #3 Conceptual
Plans delivers full detail of the alternatives for each respective lake and the factors for the use of
particular design elements. A summary follows providing representation of each alternative as it
was modeled in P8-UCM. A fourth scenario was developed to represent a situation where
Northshore and Brentwood Today Lakes were breached and return to natural streams.
Dann Safety and Flood Attenuation
The major enhancement to the Lakes for this alternative include dredging, water surface
elevation change (Northshore only), and improved outlet design. These enhancements provide
minor water quality improvement. The new discharge outlets suppress lower design flows thus
increasing hydraulic residence time for particle settling. The dredging of unconsolidated
sediment in the Lake will provide for a net removal of sediment, nutrients, and metals that have
been historically trapped. A net removal of these pollutants will prevent any re-introduction into
the system due to the mixing of high velocity flows with shallow, unconsolidated sediment
layers. The two lake systems were modeled as general devices as opposed to detention ponds due
to their complex weir configuration. The particle removal scale factor was reduced from 1.0 to
Water Quality Evaluation 9 February 2005
of Conceptual Plans
0.75 to incorporate the poor distribution of incoming flow at the headwater of the Northshore
Lake and the existence of channelized flow through the Northshore Lake (i.e., short-circuiting).
Removal scale factors less than 1.0 can be assumed to account for poor hydraulic design
(Walker, 1990). Figure 4-1 (on page 12) depicts the model's representation of the system for
this alternative.
IVater Quality Enhancements
The water quality improvement alternative utilizes a variety of design elements to ensure the
removal of a variety of pollutants as well as provide additional habitat that would promote the
well being of aquatic life. The improvements for water quality include dredging, water surface
elevation change, improved outlet design, sediment pools, variety of concentrated wetlands,
wetland shelving (Northshore only), and plunge pools for point source runoff discharges. These
improvements attempt to concentrate the settling of the largest particles at the headwaters of the
Lakes where removal of accumulated matter is more manageable. The wetlands are expected to
provide filtration of smaller particles but also promote the biological uptake and trapping of
nutrients. Both Lakes were modeled as a series of detention ponds for the sediment pool and
wetlands. Wetlands were differentiated from the sediment pools primarily by increasing the
particle removal scale factor to 3 to accommodate for additional removal of TSS and TP.
Studies performed using P8-UCM relating detention ponds vegetated with macrophytes to
particle removal factors exhibited scale factors of 2 to 3 for TSS and 3 to 6 for TP to account for
z5 to 30 percent removal (Phillips & Goyen, 1987; Lawrence, 1986). The remaining open water
area of the Lakes was modeled as a separate general device. The wetland shelves and plunge
pools were not included as model elements because they are minor in size and lack definable
continuity with the rest of the system. Figure 4-1 depicts the model's representation of the
system for this alternative.
Recommended
The Recommended alternative combines many of the aspects of the Dam Safety alternative with
some water quality enhancements. Whereas the first two alternatives have specific design
objectives, this alternative considers those objectives in addition to factors such as public
acceptance, constructability, maintainability, and economic value. The design elements for
Northshore are similar to the Water Quality Alternative. However, headwater wetlands exists in
a lower quantity and wetland shelving is limited to plunge pool areas. The volume of dredging
for this alternative is more in line to the Dam Safety alternative. For the Brentwood Today Lake,
the recommended alternative resembles the Dam Safety alternative with the addition of sediment
Water Quality Evaluation 10 February 2005
of Conceptual Plans
pools located at the headwaters of the lake and plunge pools at point source runoff discharges.
Both lake systems were modeled similarly to the Water Quality alternative except with a
reduction in the area of the wetlands at Northshore and exclusion of wetlands at Brentwood
Today Lake. Figure 4-1 depicts the model's representation of the system for this alternative.
No Lakes
The final scenario is a theoretical simulation of the natural drainage system under the future land
use. In this scenario, Northshore and Brentwood Today Lakes are replaced by streams. The No
Lakes scenario provides a baseline of current loadings, concentrations, removal efficiencies as if
the Lakes were never constructed.
Global Model Assumptions
In all alternatives, some general assumptions were made to simplify the assessment. These
assumptions are as follows:
¦ The unnamed lake south of Calvary Drive was conservatively modeled the same in all
alternatives. It was included since its efficiency is important in terms of overall efficiency of
the system.
¦ Stream reaches were modeled as pipe segments with time of concentrations estimated as the
travel time at a bank full event. Pipe segments do not account for any pollutant removal,
which P8-UCM does not have the capacity to model.
¦ Base flow was not simulated since calibration data was not available and land use did not
change from alternative to alternative (i.e., volume of base flow would not change). Base
flow simulation would have yielded minor differences in loadings and removal efficiency
since the particle data file used accounts for 100 percent filtration through the ground in four
of five particle classes and 90 percent for the fifth particle class.
¦ Each alternative was run for a statistically dry, average, and wet year and for the 1-inch Type
II SCS distribution design storm. The statistical years were developed from a 55-year record
of total precipitation values. The statistical wet and dry years were plus or minus one
standard deviation about the average, respectively.
Water Quality Evaluation » February 2005
of Conceptual Plans
DAM SAFETY AND FLOOD ATTENUATION
UPPER MIDDLE TRIBUTARY
NORTHSHORE
UNNAMED BRENTWOOD
TODAY
LOWER MAIN
WATER QUALITY IMPROVEMENTS TRIBUTARY
UPPER MIDDLE
NORTHSHORE
UNNAMED BRENTWOOD
TODAY
LOWER MAIN
RECOMMENDED TRIBUTARY
UPPER MIDDLE
NORTHSHORE
UNNAMED BRENTWOOD
LOWER TODAY
MAIN
a a a
WATERSHED DETENTION SEDIMENT WETLAND
POND POOL
Figure 4-1. Graphical depictions of the modeled networks in P8-UCM for the alternatives
Water Quality Evaluation 12 February 2005
of Conceptual Plans
4.2 Results and Findings
Several primary sets of data were retrieved from the model runs for analysis and discussion in
this section. The first set of data summarizes loadings to Northshore and Brentwood Today
Lakes from their respective watersheds. Table 4-1 displays these results and provides a
comparison of previously determined loadings from TM #2. The loadings from P8-UCM model
were developed from accumulation/wash-off dynamics of particle distributions based on NURP
data. Their export mass is a direct result of the interaction with continuous hydrologic events.
The loadings for the preliminary assessment are empirically based on studies relating land use to
storm event concentrations. The P8-UCM-based set of TSS loadings exceeds our previously
determined loadings primarily due to differences in EMCs. EMCs used in the preliminary
assessment ranged from 40-80 mg/L for TSS, while the NURP data supporting P8-UCM had a
TSS EMC of 100 mg/L. EMC's for both assessments were similar for TP and the results
reiterated that similarity. TKN, the predominant particulate form of nitrogen, is modeled in P8-
UCM since the primary removal mechanism of the model is settling. A direct comparison of TN
versus TKN loadings is not valid. However, the values have been provided below as a reference.
Table d-1
Comparison of Pollutant Loadings from the PreliminaryAssessvtent and the Model
TSS 168,840 260,691 116,210 207,971
TP 840 833 560 667
TN/TKN 7,300(TN) 3,748(TKN) 6,020(TN) 3,002(TKN)
NOTES: Loadings are presented in Ibs/year. Preliminary loadings for TN only. Final loadings for TKN only.
Tables 4-2, 4-3, and 4-4 summarize the removal efficiency of pollutants for the overall system.
The data included within these tables reflects the relative comparison of the alternatives and a
theoretical simulation of the system with no Northshore and Brentwood Today Lakes. Median
values of pollutant removal efficiency have been referenced from the National Pollutant
Removal Database for Stornnvater Treatment Practices, 2"d Edition developed by the Center for
Watershed Protection and authored by Rebecca Winer. These values provide a baseline for
evaluation; however it must be understood that those median values represent a multitude of sites
under varied design conditions (new construction, retrofit, etc).
Watcr Quality Evaluation 13 February 2005
of Conceptual Plans
Table 4-2
Overall TSS Retiioval Efficiency (17c)
Hydrologic ?.
Average 71 81 76 10
1- Inch Design 62 73 67 9
NOTE: Removal efficiency measured in %.
TSS removal efficiencies ranged from 71 to 81 percent for the average year and 62 to 73 percent
for the 1-inch design storm. Median baseline levels of TSS removal for regional wet detention
ponds and stormwater wetlands are 70 and 80 percent, respectively (Winer, 2000). The Dam
Safety alternative, which contains only wet detention ponds as the main design element, is inline
with this median baseline level. The other alternatives, which include sediment pools and
wetlands, provide only minor increases (z5 percent) on this efficiency and are also in line with
the median baseline level (80 percent). The Recommended and Water Quality alternatives show
improvement in the removal efficiency of the middle two particle classes (P30, P50) as shown in
Figure 4-2. The removal of these particles is directly attributable to the filtering capacity of
wetlands. Dissolved particles (PO) are not significantly removed in any alternative.
Figure 4-2
Removal Efficiency (%) for Discrete Particles
100
90
80
a
70
U
d 60
U
50
w
40
E 30
cc 20
10
0

PO P10 P30 P50 P80
Particle Distribution
- -Dam Safety --o Recommended Water Quality
The preliminary assessment of TM #2 expressed removal efficiency of 80 percent for the overall
system in its current state. The efficiencies selected for Northshore and Brentwood Today Lakes
that culminated in that overall efficiency were likely over estimated; also, that assessment does
Water Quality Evaluation 14 February 2005
of Conceptual Plans
not consider the conservative modeling of the unnamed lake upstream of Northshore Lake,
which reduced overall efficiency in this analysis. Removal efficiencies for the wet and dry year
were within two percent of the efficiency expressed for the average year. The No Lakes scenario
provides minor TSS removal (=10 percent), which is solely attributable to the efficiency of the
unnamed lake.
Table 4-3 displays overall TP removal efficiencies for the alternatives and the No Lakes
scenario. TP removal efficiencies ranged from 38 to 50 percent for the average year and 28 to 40
percent for the 1-inch design storm. Median baseline levels of TP removal for regional wet
detention ponds and stormwater wetlands are 48 and 43 percent, respectively (Winer, 2000). The
Dam Safety alternative, which contains only wet detention ponds as the main design element,
performs below the median level. The other alternatives, which include sediment pools and
wetlands, provide only minor increases (z6 percent) on this efficiency, as expected and are also
in line with the median baseline level (48 percent). The values in Table 4-3 only report TP
removed by settling. It would be expected that as TP breaks down into a non-particulate, bio-
available form (orthophosphorus), nutrient uptake would occur. The nutrient uptake would
improve upon the removal efficiencies displayed in this table for alternatives that include a
wetland. It is difficult to pinpoint the expected removal efficiency attributed to nutrient uptake
as water chemistry and vegetation selection would be major factors in the performance of the
wetland. It could also be expected that during winter months or poor wetland maintenance, that
the wetland would decrease removal efficiency or even be a source of TP.
Table 4-3
Overall TP Removal Efficiency (cle)
Average 38 50 44 4
1- Inch Design 28 40 33 3
NOTE: Removal efficiency measured in %.
The preliminary assessment of TM #2 expressed removal efficiency of 56 percent for the overall
system in its current state. The efficiencies selected for Northshore and Brentwood Today Lakes
that culminated in that overall efficiency were likely over estimated; also, that assessment does
not consider the conservative modeling of the unnamed lake upstream of Northshore Lake.
Removal efficiencies for the wet and dry year were within 1 percent of the efficiency expressed
for the average year. The No Lakes scenario provides minor TP removal (z4 percent), which is
primarily attributable to the efficiency of the unnamed lake.
Water Quality Evaluation 15 February 2005
of Conceptual Plans
Table 4-4 displays overall TKN removal efficiencies for the alternatives and the No Lakes
scenario. TKN removal efficiencies ranged from 33 to 44 percent for the average year and 24 to
36 percent for the 1-inch design storm. Median baseline levels of TN removal for regional wet
detention ponds and stormwater wetlands are 37 and 35 percent, respectively (Winer, 2000).
TKN represents the primarily settleable component of TN. Therefore, it can be roughly assumed
that design elements involving only removal by settling would equate TN and TKN removal
efficiency. The Dam Safety alternative, which contains only wet detention ponds and, therefore,
emphasizes particulate settlement as its primary removal mechanism, performs in line with the
median baseline level for TN. The other alternatives, which include sediment pools and
wetlands, provide only minor increases (z6 percent) on this efficiency. The values in Table 4-4
only report TKN removed by settling. It would be expected that as TKN breaks down and
transforms into non-particulate, bio-available forms, such as ammonium (N1-14+) and nitrite-
nitrate (NOZ -NO3-) nutrient uptake would occur. The nutrient uptake would improve upon the
removal efficiencies displayed in this Table for alternatives that include a wetland. The median
level of NO,, removal in a stormwater wetland versus as wet pond is triple (68 versus 23 percent).
It is difficult to pinpoint the expected removal efficiency attributed to nutrient uptake as water
chemistry and vegetation selection would be major factors in the performance of the wetland. It
could also be expected that during winter months or poor wetland maintenance, that the wetland
would decrease removal efficiency or even be a source of TN/TKN.
Table 4-4
Overall TKN Removal Efficiency (%)
Hydrologic ?. . .
Average 33 44 38 4
1- Inch Design 24 36 29 2
NOTE: Removal efficiency measured in %.
The preliminary assessment of TM #2 expressed removal efficiency for TN of 31 percent for the
overall system in its current state. That estimation was fairly accurate as the TKN removal for
the Dam Safety alternative is within range. Removal efficiencies for the wet and dry year were
within 1 percent of the efficiency expressed for the average year. The No Lakes scenario
provides minor TKN removal (z4 percent), which is primarily attributable to the efficiency of
the unnamed lake.
Tables 4-5, 4-6, and 4-7 summarize the cumulative load entering the stream downstream of
Brentwood Today Lake. Once again, the strength of P8-UCM is not in absolute prediction of
loadings and concentrations; therefore, the alternatives were executed and reported for a
Water Quality Evaluation 16 February 2005
of Conceptual Plans
statistically dry, average, and wet year off rainfall volume. These results demonstrate the range
of loading that could occur under different hydrologic conditions and during a typical design
storm (1-inch SCS Type II distribution). These values may provide reference in determining
downstream impacts.
Table 4-5
TSS Loading (Ibs ) discharged out of Brentwood Today Lake
Hydrologic Even t 111111111110
Dry 126,500 86,100 106,500 379,500
Average 137,000 91,200 113,700 421,300
Wet 168,500 113,400 141,100 503,600
1- Inch Design 4,300 3,000 3,700 10,300
NOTE: Loadings measured in Ibs.
Table 4-G
TP Loading (lbs) discharged out of Brentwood Today Lake
Dry 840 680 760 1,390
Average 930 750 840 1,440
Wet 1,120 900 1,020 1,700
1- Inch Design 20 20 20 40
NOTE: Loadings measured in Ibs.
Table 4-7
TKN Loading (Ibs) discharged out of Brentwood Today Lake
Dry 4,060 3,390 3,750 5,800
Average 4,530 3,780 4,170 6,500
Wet 5,410 4,530 5,000 7,700
1- Inch Design 130 110 120 160
NOTE: Loadings measured in Ibs.
Water Quality Evahtatiorn 17 February 2005
of Conccptrtal Platis
SECTION 5.0 - MODEL EVALUATION
5.1 Continuity Errors
P8-UCM performs continuous water-balance and mass-balance checks for single devices and the
entire network. Differences in these checks are identified as continuity errors, which can be
highlighted to the user through the setting of a maximum continuity difference. These continuity
errors are typical of devices with large, rapid fluctuations in volume (e.g., swales/buffers, smaller
detention ponds) (Walker, 1990). Continuity errors can be controlled through a reduced time
step. It was necessary in this modeling effort to run all scenarios with a time step = 8, in order to
reduce continuity errors within the smaller detention ponds representing sediment pools. A
comparison analysis of a particular model run at a time step = 1 and = 8 demonstrated minor
differences in removal efficiency results (less than 1.5 percent). Concentrations and loads
demonstrated slightly higher differences (2 to 6 percent) with the higher end of these differences
occurring in the TSS concentrations.
5.2 Sensitivity Analysis
As previously discussed, P8-UCM and other water quality models exhibit a high level of
variability. Many of the parameters used within this model are based upon estimation and
generalized calibrations; therefore, it is beneficial to understand which of these parameters may
significantly impact the results when not properly quantified. P8-UCM includes a utility that
automates sensitivity analysis for a desired scenario. The sensitivity analysis utility groups input
parameters into four categories: watershed, device, storm, and particle. The parameters for the
first three of these groups are typically user defined and the final group, particle, include default
parameters.
A sensitivity analysis was performed for the water quality scenario since it included the full
range of devices and their parameters. This analysis was run for the average precipitation year
and the variables were increased 25 percent individually. There were two primary observations
from the results of this analysis. Removal efficiencies were less affected than outflow
concentrations by the change in parameters. This reinforces the value of the model as a relative
predictor among scenarios. The second observation showed that the most variable parameters
were in the particle group; a default group of data based on field and laboratory data collected
from a multitude of sites for the NURP program. The parameters demonstrating the highest
variability were the accumulation rate, accumulation decay rate, and wash-off exponent. Their
sensitivity measured as percent change for removal efficiencies and concentrations ranged from
near 0 to 21.6 percent and 3.6 to 24.8 percent, respectively. The high variability in wash-off
Watcr Quality Evaluation 18 February 2005
of Conceptual Plaits
exponent is due to the exponential response it yields in comparison to linear coefficients
(Walker, 1990). Watershed areas and storm volumes also produced a significant sensitivity as
expected, however they are parameters that can be calculated with confidence.
SECTION 6.0 - CONCLUSION AND DISCUSSION
The purpose of this TM and water quality evaluation was to develop sound input for the relative
evaluation of several proposed alternatives. These alternatives were developed to reestablish or
improve lost functions of Northshore and Brentwood Today Lakes. It was determined that a
modeling effort would provide an objective means of evaluation of these alternatives with
respect to water quality. P8-UCM, an urban runoff model, was selected as a tool that could
objectively evaluate a range of scenarios with limited data. The P8-UCM modeling effort
allowed for the creation of baseline input data, definition of several design elements or BMPs,
and simulation of physical pollutant removal processes. The modeling effort yielded several
sets of data that could be conservatively interpreted into water quality benefits of the varying
alternatives. The water quality benefits are an essential determining factor, but not the only
factor, for the selection and implementation of an alternative for rehabilitation of Northshore and
Brentwood Today Lakes.
Based on this evaluation of pollutant loadings and BMP removal efficiency with results from the
Preliminary Assessment and nationally/regionally expected performance levels the following
conclusions are made:
¦ The use of NURP calibrated particle distribution data allows for the discrete mass
accumulation and removal of particles and their bound pollutants. Regional EMC values
would produce more representative loading but do not provide for accurate removal
efficiency development. Removal efficiency development was a goal of this effort.
¦ Overall pollutant removal efficiencies for TSS did not improve significantly. As expected the
existing lake systems function well with regards to settling out of TSS. However, the
existing system does not provide an accessible, cost effective means of permanently
removing sediment that can be achieved with a sediment pool.
¦ Overall pollutant removal efficiencies for the middle ranged particles (P30 and P50) are
higher in alternatives that include a wetland. There is no significant change in removal for
large particles (P80) and dissolved particles (PO) in any alternative.
Water Quality Evaluation 19 February 2005
of Conceptual Plats
¦ Pollutant removal efficiencies for TP are expected to be higher in the Water Quality and
Recommended alternative than reported. P8-UCM does not account for orthophosphorus
uptake in wetlands, which could significantly increase TP removal.
¦ Pollutant removal efficiencies for TN would be expected to be lower than reported TKN
removal values as TKN is a single component of TN. However, these efficiencies should
bounce back for the Water Quality and Recommended alternative. P8-UCM does not
account for ammonium or nitrite/nitrate uptake in wetlands, which could significantly
increase overall TN removal.
¦ The TN removal efficiency for the Water Quality and Recommended alternative should
fulfill a TN reduction of at least 30 percent per Neuse River Nutrient Management Strategy,
although that requirement is for singular, new development.
¦ Furthermore, pollutant removal efficiencies may be negatively impacted without proper
maintenance and harvesting of BMPs that present the opportunity to permanently remove
pollutants from the Lakes system.
¦ The addition of wetlands and sediment pools would provide for more laminar flow regions
near the headwaters of the lake and increase hydraulic residence time. These changes could
increase the potential for fecal coliform die off and lessen downstream impact through
ultraviolet radiation and longer travel time.
This water quality evaluation provides evidence that the Recommended and Water Quality
alternative demonstrate improvement in pollutant removal efficiency over the Dam Safety
alternative, which provides better function of flood control over existing lake conditions by
reconfiguration and construction of new spillways. The relative water quality results of the
alternatives and other benefits of the inclusive design elements should be taken from this TM
and used in the global evaluation of alternatives to be discussed further in an Alternative
Design Summary and Final Report. Their level of value must be weighed against results of
other analyses to determine the best alternative for Northshore and Brentwood Today Lakes.
Water Quality Evaluation 20 February 2005
of Conceptual Plans
SECTION 7.0 - REFERENCES
Haith, D.A. and L.L. Shoemaker, 1987. "Generalized Watershed Loading Functions for Stream
Flow Nutrients", Water Resources Bulletin, American Water Resources Association, Vol. 23 No.
3.
Hamon, W.R., 1961. "Estimating Potential Evapotranspiration", Proceedings of the American
Society of Civil Engineers, Journal of Hydraulics Division, Vol. 87, No. HY3.
US Environmental Protection Agency, 1992. Compendium of Watershed-Scale Models for
TMDL Development, Washington D.C., 841R94002.
US Environmental Protection Agency, 1999. Protocol for Developing Nutrient TMDLs,
Washington D.C., 841B99007.
Wright-McLaughlin Engineers, 1969. Urban Storm Drainage Criteria Manual, Denver, Colorado.
Soil Conservation Service, 1986. Urban Hydrology for Small Watersheds, Technical Release
No. 55, US Department of Agriculture, Washington D.C.
Walker, William W, Jr. Ph.D., 1990. P8 Urban Catchment Model: Program Documentation,
Concord, Massachusetts.
Winer, Rebecca, 2000. National Pollutant Removal Performance Results for Stormwater
Treatment Devices, 2°`' Edition. Center for Watershed Protection, Elliot City, Maryland.
Water Quality Evaluation 21 February 2005
of Conceptual Plans
Northshore/Brentwood Today Lakes - Adjacent Property Owners
PIN # OWNER Mailin Address Mailing Address 2 Mailin Address 3 Lot Description Street # Street Name Street T e
1725.0519 7143 SIMMONS, VINCENT L & SHELIA B
- 4016 INGRAM DR RALEIGH NC 27604-3406 LT 52 BLK 25 BRENTWOOD ESTS SECT 10 PT C 4016 INGRAM DR
1725.0519 9140 DICKSON, HOWARD KENNETH JR K
KAREN 3900 BEAUMONT CT RALEIGH NC 27604.3452 LT 10 BRENTWOOD TODAY PH III BM 1978.670 3900 BEAUMONT CT
1725.05 29 0026 BRANCH, STEVE & VALERIE C 3904 BEAUMONT CT RALEIGH NC 27604.3452 LOT 11 BRENTWOOD TODAY PH III 3904 BEAUMONT CT
1725.0519 7034 BURRELL, JOSEPHINE H 4012 INGRAM DR RALEIGH NC 27604-3406 LT 51 BLK 25 BRNTWD ESTS SEC 10 PT C 4012 INGRAM DR
1725.0518 7935 BAILLIE, JAMES C 4008 INGRAM DR RALEIGH NC 27604.3406 LT 50 BLK 25 BRENTWOOD EST SEC 10 PT C 4008 INGRAM DR
1725.0518 9982 SHACKLEFORD, ROGER J & JILMA C 3901 PEPPERTREE PL RALEIGH NC 27604.3442 L 18 BRENTWOOD TODAY PH III BM 1978.670 3901 PEPPERTREE PL
1725.0518 7807 BRIDGER, ROBERT CAMERON &SANDRA GAIL MERA 4004 INGRAM DR RALEIGH NC 27604.3406 LT 49 BRENTWOOD EST SEC 10 PT C 1967.180 4004 INGRAM DR
1725.0518 9883 NGUYEN, XUAN VAN & XAM THI DO 3900 PEPPERTREE PL RALEIGH NC 27604-3443 L 19 REV BRENTWOOD TODAY PH 31981.26 3900 PEPPERTREE PL
1725.05 28 0768 MIRCHANDANI, SHARON L 3904 PEPPERTREE PL RALEIGH NC 27604-3443 LOT 20 BRENTWOOD TODAY PHASE III 3904 PEPPERTREE PL
1725.0518 6860 KRIEGSMAN, JEFF 0 4000 INGRAM DR RALEIGH NC 27604.3406 L48 BL 25 BRENTWD EST SC10 PT C BM67-180 4000 INGRAM DR
1725.0518 6723 VOCKEROTH, ALFRED F JR &KATHLEEN J 3920 INGRAM DR RALEIGH NC 27604.3404 LT 47 BLK 25 BRENTWOOD ESTS SEC 10 PT C 3920 INGRAM DR
1725.05 28 0636 BROWN, WILL S III & DEBORAH M 3901 OLD CREEK CT RALEIGH NC 27604.3455 LOT 25 BRENTWOOD TODAY PH III 3901 OLD CREEK CT
1725.0518 5686 LIGGINS, DAVID RICKY & DEBORAH C 3916 INGRAM DR RALEIGH NC 27604-3404 LT 46 BL 25 BRENTWD EST SEC 10 PT C 3916 INGRAM DR
1725.05 28 0537
1725.0518 5549 MUNK, DON E & CHILI CHU LIN
PARKER, JOHN RANDOLPH JR &DORIS B 3900 OLD CREEK CT
3912 INGRAM DR RALEIGH NC 27604-3454
RALEIGH NC 27604.3404 LT 26 BRENTWOOD TODAY PH 3 BM 1978-670
L 45 BL 25 BRENTWD EST SEC 10 PT C 3900
3912 OLD CREEK
INGRAM CT
DR
1725.05 28 0479 BARRESI, PATRICIA EILEEN BOURS 3904 OLD CREEK CT RALEIGH NC 27604.3454 LT 27 BRENTWOOD TODAY PH III BM78-670 3904 OLD CREEK CT
1725.0518 5522 FERRARO, MICHAEL VINCENT 4300 BLAND RD RALEIGH NC 27609-6125 LT 44 BLK 25 BRENTWOOD ESTS SECT 10 PT C 3908 INGRAM DR
1725.0518 5405 PILKINGTON, ALBERT JR & CARLINE 3904 INGRAM DR RALEIGH NC 27604.3404 LT 43 BL 25 BRENTWD EST SEC 10 PT C 3904 INGRAM DR
1725.0518 4387 ROSE, LARRY B & OPE F 3900 INGRAM DR RALEIGH NC 27604.3404 L 42 BL 25 BRENTWD EST SC 10 PT C 67.180 3900 INGRAM DR
1725.0518 9391 KOONS, DARREN J & HEATHER HUGHES 3633 GREYWOOD DR RALEIGH NC 27604.3462 LT 33 BRENTWOOD TODAY PH 4 BM 1980-678 3633 GREYWOOD DR
1725.0518 4269 BAILEY, LORILYN & STEPHEN E 3828 INGRAM DR RALEIGH NC 27604.3316 LT 41 BLK 25 BRENTWD ESTS SEC 10 PT C 3828 INGRAM DR
1725.0518 9236 MACENTEE, JASON D & ERIN E DOUGH 3629 GREYWOOD DR RALEIGH NC 27604.3462 LOT 34 BRENTWOOD TODAY PHASE 4 3629 GREYWOOD DR
1725.0518 4241 BAILEY, STEPHEN E & LORILYN 3824 INGRAM DR RALEIGH NC 27604.3316 L 40 BL 25 BRENTWD EST SEC 10 PT C 3824 INGRAM DR
1725.05 18 8270 JOHNSON, TYRONE B & AGNES C 3625 GREYWOOD DR RALEIGH NC 27604.3462 LT 35 BRENTWOOD TODAY PH 4 BM 1980-642 3625 GREYWOOD DR
1725.0518 4114 WILLIAMS, ALVIN & ANNIE S 3820 INGRAM DR RALEIGH NC 27604.3316 LT 39 BLK 25 BRENTWOOD ESTS SECT 10 PT C 3820 INGRAM DR
1725.0518 8123
1725.0518 4006 ELLIOTT, PAUL WAYNE & TERESA L
ARCHER, KEIRA T 3621 GREYWOOD DR
3816 INGRAM DR RALEIGH NC 27604.3462
RALEIGH NC 27604.3316 LT 36 BRENTWOOD TODAY PH 4 (BM1980.678)
L38 & SM ADJ ST BL 25 BRENTWD EST S10 P 3621
3816 GREYWOOD
INGRAM DR
DR
1725.0518 7097 LAHOUD, MICHAEL A 3617 GREYWOOD DR RALEIGH NC 27604-3462 LT 37 BRENTWOOD TODAY PH 4 BM1980.678 3617 GREYWOOD DR
1725.0518 7002
1125.0517 4908 FRANZEL, RONALD A & ANN Z
ADESUYI, ISRAEL 0 & JACQUELINE MUS DEPARTMENT OF HUD, HOFPA 3613 GREYWOOD DR
ATTN: SEC-HELD SF NOTES, RM 6240 RALEIGH NC 27604.3462
PO BOX 44813
WASHINGTON DC 20026.4813 LT 38 BRENTWOOD TODAY PHASE 4 (BM80-678
L37 BL 25 BRENTWD ESTS SC 10 P C SM ST 3613
3812 GREYWOOD
INGRAM DR
DR
1725.0517 6936 FREEZE, DAVID A 3609 GREYWOOD DR RALEIGH NC 27604-3462 LT 39 BRENTWOOD TODAY PH 4 BM 1979.224 3609 GREYWOOD DR
1725.0517 4819 FLOWERS, AYDREN D & JEANNETTE P 3808 INGRAM DR RALEIGH NC 27604.3316 LT 36 BLK 25 BRENTWOOD ESTS SEC 10 PT C 3808 INGRAM DR
1725.0517 6837 RIVERA, MANUAL C & DORALICIA D M 3605 GREYWOOD DR RALEIGH NC 27604.3462 LT 40 BRENTWOOD TODAY PH 4 BM 1979-224 3605 GREYWOOD DR
1725.0517 4800 HOULE, RICKY D 3804 INGRAM DR RALEIGH NC 27604.3316 LT 35 BLK 25 BRENTWD ESTS SEC 10 PT C 3804 INGRAM DR
1725.0517 6727
1725.0517 2782 THORPE, BRIAN R
HIGGINS, REGINALD R 3601 GREYWOOD DR
3800 INGRAM DR RALEIGH NC 27604.3462
RALEIGH NC 27604.3316 LT 41 BRENTWOOD TODAY PH 4 IBM 1979-224)
LT 34 BILK 25 BRENTWD ESTS SEC 10 PT C 3601
3800 GREYWOOD
INGRAM DR
DR
1725.05 17 6609 BRITTON, RHONDA K 3533 GREYWOOD DR RALEIGH NC 27604-3347 LT 42 BRENTWOOD TODAY PH 4 BM 1979-224 3533 GREYWOOD DR
1725.0517 4606 SMITSHON, ELLA W 3804 CAMARO CT RALEIGH NC 27604.3306 LT 33 BLK 25 BRENTWD EST SEC 10 PT C 3804 CAMARO CT
1725.05 17 5680 PITTMAN, OLIVER L & ANITA M 3529 GREYWOOD DR RALEIGH NC 27604-3347 LT 43 BRENTWOOD TODAY PH 4 BM 1979.224 3529 GREYWOOD DR
1725.0517 3586 VIKLUND, VICTOR L & KATHLEEN G 3808 CAMARO CT RALEIGH NC 27604.3306 LT 32 BLK 25 BRENTWOOD ESTS SECT 10 PT C 3808 CAMARO CT
1725.09 17 3423 DANIEL, WILLIAM L JR & CLAUDIA C 3809 CAMARO CT RALEIGH NC 27604.3305 LT 31 BLK 25 BRENTWD ESTS SEC 10 PT C 3809 CAMARO CT
1725.0517 5544 TURNER, JAMES HENRY 3527 GREYWOOD OR RALEIGH NC 27604.3347 LT 90 ADDT TO BRENTWOOD TODAY BM1980.921 3527 GREYWOOD DR
1725.0917 5435 DUNN, DWIGHT & ANNA M 3525 GREYWOOD OR RALEIGH NC 27604.3347 LT 91 ADDT TO BRENTWOOD TODAY BM1980-921 3525 GREYWOOD DR
1725.09171395 WOOMER, CLARK FULTON 3717 MARLIN CT RALEIGH NC 27604.3319 LT 19 BLK 25 BRENTWD EST SEC 10 PT B 3717 MARLIN CT
1725.09 17 4399 JOHNSON, TRACEY A &DONNA R JOHNSON 3523 GREYWOOD DR RALEIGH NC 27604.3347 LT 92 ADDT TO BRENTWOOD TODAY BM1980.921 3523 GREYWOOD DR
1725.09 17 4341 PRESSLEY, CHRISTINA J & MATTHEW S 3521 GREYWOOD DR RALEIGH NC 27604.3347 LT 93 ADDT TO BRENTWOOD TODAY BM 1980-921 3521 GREYWOOD DR
1725.09 17 3271 BARBOUR, DANIEL M & LINDA T 3517 GREYWOOD DR RALEIGH NC 276043347 LT 94 ADDT TO BRENTWOOD TODAY BM90.1210 3517 GREYWOOD DR
1725.09 17 2214 RYAN, DANIEL J 3720 MARLIN CT RALEIGH NC 27604-3320 LT 18 ELK 25 BRENTWD ESTS SEC 10 PT B 3720 MARLIN CT
1725.09 17 1164 MARR, CLYDE M III & ELLEN R 3716 MARLIN CT RALEIGH NC 27604-3320 L17 BL25 BRENTWD ESTS SC10 PT B BM66.241 3716 MARLIN CT
1725.09 17 3121 BAKER, JEANNETTE 3513 GREYWOOD DR RALEIGH NC 276043347 LT 95 ADDT TO BRENTWOOD TODAY BM1980.921 3213 GREYWOOD DR
1725.0916 2955 ADAMS GILT COMPANY THE PO BOX 18108 RALEIGH NC 27619-8108 LT 96 ADDT TO BRENTWOOD TODAY BM1980.921 3509 GREYWOOD DR
1725.0916 0997 BINGHAM, WILLIAM D & PEGGY H 3713 LANCELOT CT RALEIGH NC 27604-3317 LT 8 ELK 25 BRENTWOOD EST SEC 10 PT B 3713 LANCELOT CT
1725.09 16 1813 HUNTER, LEWIS JR & JACQUELINE B 3716 LANCELOT CT RALEIGH NC 27604.3318 LT 7 BLK 25 BRENTWD ESTS SEC 10 PT B 3716 LANCELOT CT
1725.0916 0744 MOORE, SCOTT E 3712 LANCELOT CT RALEIGH NC 27604-3318 LT 6 BLK 25 BRENTWOOD ESTS SC 10 PT B 3712 LANCELOT CT
1725.0916 2607 BILGER, GEORGE JR 3409 GREYWOOD DR RALEIGH NC 27604-3349 LT 101 ADD TO BRENTWOOD TODAY BM90.1210 3409 GREYWOOD DR
1725.0916 0508 ROBERTS, DON LEE & PAULA M 3312 HUNTLEIGH DR RALEIGH NC 27604.3312 LT 1-A BLK 25 BRENTWOOD EST SEC 9 PT C 3312 HUNTLEIGH DR
1725.0916 2500 GALLANT, DANIEL R & VIVIENNE M 3405 GREYWOOD DR RALEIGH NC 27604.3349 LT 102 ADD TO BRENTWOOD TODAY BM1980.921 3405 GREYWOOD DR
1725.09 16 1415 EDUCARE COMMUNITY LIVING CORP 10140 LINN STATION RD LOUISVILLE KY 40223.3813 L 1 BL 25A BRENTWD EST SC 11 BM70.288 3300 HUNTLEIGH DR
1726.18 20 6533 NORTHSHORE HOMEOWNERS ASSOCC/0 JAMES F & MARTHA B WILLIAMS 4313 WATERBURY RD RALEIGH NC 27604.3546 NORTHSHORE LAKE 0 COMSTOCK RD
1726.17 201018 SOUTHERLAND, JIMMIE H &RALEIGH DOUGLAS SOUTHERLAND JR 4308 RYEGATE OR RALEIGH NC 27604.3501 LT 10 ELK A NORTHSHORE SECT 1 4308 RYEGATE DR
1726.17 20 0015 LISOWE, DAVID G 4304 RYEGATE DR RALEIGH NC 27604.3501 LT 9 BLK A NORTHSHORE SEC 1 BM 1968-184 4304 RYEGATE DR
1726.17 10 9013 BROWN, LINDA W 4120 PITTSFORD RD RALEIGH NC 27604-3459 LT 8 BLK A NORTHSHORE SEC 1 BM 1968-184 4120 PITTSFORD RD
1725.06 29 7933 LAWTON, CAROLYN DIANE 3113 DEANA LN RALEIGH NC 27604-3478 LT 40 ELK A NORTHSHORE SEC 1 BM1968.184 3111 DEANA LA
1725.06 29 8924 GRADUS, PAUL A & BECKWITH S 816 MOUNT VERNON CHURCH RD RALEIGH NC 27614-9283 LT 39 ELK A NORTHSHORE SECT 1 3117 DEANA LA
1725.06 29 6817 CHATHAM, BOBBY CLARKC/O POLLY CHATHAM 8121 LAKISTA POINT LN GARNER NC 27529-9096 LT 41 BL A NORTH SHORE SEC 1 3101 NEW HOPE CHURCH RD
1725.0519 9932 SMITH, ANDRE C & SANDRA WALLACE 4116 PITTSFORD RD RALEIGH NC 27604-3459 LT 7 BLK A NORTHSHORE SEC 1 4116 PITTSFORD RD
1725.0519 9864 WEAVER, HUEY P & DOROTHY A 4112 PITTSFORD RD RALEIGH NC 27604.3459 LT 6 BLK A NORTHSHORE SEC 1 4112 PITTSFORD RD
Northshore/Brentwood Today Lakes - Adjacent Property Owners
PIN # OWNER Mailin Address Mailin Address 2 Mailin Address 3 Lot Description Street # Street Name Street T e
1725.0519 9786 KODACK, JONATHAN A & JULIE G 4108 PITTSFORD RD RALEIGH NC 27604.3459 LT 5 BL A NORTHSHORE SC 1 BM1968.184 4108 PITTSFORD RD
1725.05 291730 CHATHAM, B CLARK & POLLY 1 8121 LAKISTA POINT LN GARNER NC 27529-9096 LT 2 BLK A NORTHSHORE SEC 1 3005 NEW HOPE CHURCH RD
1725.05 29 2761 CHATHAM, B CLARK & POLLY 1 8121 LAKISTA POINT LN GARNER NC 27529-9096 LT 1 BLK A NORTHSHORE SEC 1 3019 NEW HOPE CHURCH RD
1725.0519 8700 TOMLINSON, JANET M 4109 PITTSFORD RD RALEIGH NC 27604-3458 LT 7 BLK B NORTHSHORE SECT 1 4109 PITTSFORD RD
1725.0519 6679 BRADY, WILLIE G & JANET S 329 MOSS RD ZEBULON NC 27597.8805 LT 45 SHAMROCK MEADOW SECT 1 2920 DUNSINANE CT
1725.05 29 0618 WOODALL, WILLIAM A & MARY B 4104 PITTSFORD RD RALEIGH NC 27604-3459 LT 4 BLK A NORTHSHORE SECT 1 4104 PITTSFORD RD
1725.0519 8631 FERGUSON, ARTHUR E JR & SUSAN H 4105 PITTSFORD RD RALEIGH NC 27604-3458 LT 6 BL B NORTHSHORE SC 1 BN11968.184 4105 PITTSFORD RD
1725.0519 6670 BERGMAN, WILLIAM C & ELLEN M 2916 DUNSINANE CT RALEIGH NC 27604.3417 LT 44 SHAMROCK MEADOW SEC 1 2916 DUNSINANE CT
1725.05 29 0549 KALU, NENA 3001 NEW HOPE CHURCH RD RALEIGH NC 27604-3427 LT 3 BLK A NORTHSHORE SEC 1 4100 PITTSFORD RD
1725.0519 8571 PIOTROWSKI, STEPHEN & NANCY S 4101 PITTSFORD RD RALEIGH NC 27604.3458 LT 5 BLK B NORTHSHORE SEC 1 4101 PITTSFORD RD
1725.0519 7478 LATKOWSKI, PATRICIA B 2919 NEW HOPE CHURCH RD # R RALEIGH NC 27604.3425 LT 4 BLK B N SHORE SEC 1 2919 NEW HOPE CHURCH RD
1725.05 291303 BEATTY, ROSEMARY 3909 BEAUMONT CT RALEIGH NC 27604.3453 LT 7 BRENTWOOD TODAY PH 1 3909 BEAUMONT CT
1725.05 29 0300 KUO, LIU KUIE HELEN 3905 BEAUMONT CT RALEIGH NC 27604.3453 LOT 8 BRENTWOOD TODAY PHASE ONE 3905 BEAUMONT CT
1725.0518 7587 ADAMS BILT COMPANY THE PO BOX 18108 RALEIGH NC 27619-8108 ARNOLD LD 0 SARATOGA DR
1725.0519 9251 PEARSON, SCOTT C TRUSTEE 222 MONTIBELLO DR CARY NC 27513.2466 LOT 9 BRENTWOOD TODAY PHASE ONE 3901 BEAUMONT CT
1725.0519 7212 FRYE, HARLAN E 2908 NEW HOPE CHURCH RD RALEIGH NC 27604.3426 LT 53 BL 25 BRENTWD EST S10 PT C (ADD) 2908 NEW HOPE CHURCH RD
1726.18 32 4278 GRIT NC LLCC/0 MARVIN F POER & CO ATTN: RAV 4 EXECUTIVE PARK W STE 100 ATLANTA GA 30329-2212 PROP NORTH BOULEVARD PLAZA BM 1984-212 4702 BAYRIDGE CRSG
1726.18 321016 MASSENGALE, SUSAN L 4616 WATERBURY RD RALEIGH NC 27604.3553 L224 PT L223 SHAMROCK MDWS SC 5 84.930 4616 WATERBURY RD
1726.18 31 2936 DIDKIVSKA, GANNA &VOLODYMYR DIDKIVSKYY 4600 WATERBURY RD RALEIGH NC 27604.3553 L7 BL G NTHSHORE SC5 PT 223 SHAMROCK MDW 4600 WATERBURY RD
1726.18 310838 LANGLEY, BOBBIE LEWIS HARWARD 4613 WATERBURY RD RALEIGH NC 27604.3552 LT 222 SHAMROCK MEADOW SEC 5 BM1973.391 O WATERBURY RD
1726.18 21 9850 SHARPE, JUDITH P 4608 PAISLEY PL RALEIGH NC 27604-3532 LT 220 SHAMROCK MEADOW SEC 5 BM1971.200 4608 PAISLEY PL
1726.18 31 0766 LE, LANH THI MELVIN 307 WINDEL DR RALEIGH NC 27609.4443 LT 10 BLK F N SHORES SEC 5 4517 WATERBURY RD
1726.18 21 8792 FORE, CLAYTON LEWIS 4604 PAISLEY PL RALEIGH NC 27604-3532 LT 219 SHAMROCK MEADOW SEC 5 4604 PAISLEY PL
1726.18 31 0615 REED, WILLIAM S & ELIZABETH B 4513 WATERBURY RD RALEIGH NC 27604.3550 LT 9 BLK F NORTHSHORE SEC 5 4513 WATERBURY RD
1726.18 217663 MESSENGER, JUN GILLS 3109 SELKIRK DR RALEIGH NC 27604-3541 LT 206 SHAMROCK MEADOW SEC 5 3109 SELKIRK PL
1726.18 31 0516 BARWICK, ALLEN J & CAROL B 4509 WATERBURY RD RALEIGH NC 27604.3550 LT 8 BLK F NORTHSHORE SEC 5 4509 WATERBURY RD
1726.18 218443 ROSSI, LAWRENCE 0 SR & MOZELL H 3113 COMSTOCK RD RALEIGH NC 27604-3506 LT 4 BLK F NORTHSHORE SEC 5 3113 COMSTOCK RD
1726.18 21 7543 NIPPER, JOHN BLOISE JR & LINDA JEAN 3112 SELKIRK DR RALEIGH NC 27604-3542 LT 205 SHAMROCK MDW SEC 5 3112 SELKIRK PL
1726.18 217327 BIRGER, BORIS L 3109 COMSTOCK RD RALEIGH NC 27604-3506 LT 3 BLK F NORTHSHORE SEC 3 3109 COMSTOCK RD
1726.18 219211 LUBBERS, JEFFREY A & CAROL A 3116 COMSTOCK RD RALEIGH NC 27604.3507 LT 25 BLK A NORTHSHORE SEC 5 3116 COMSTOCK RD
1726.18 218135 PEREZ, POLICARPIO CARRASCO &BLANCA ESTELA REYES 3112 COMSTOCK RD RALEIGH NC 27604.3507 LT 24 BLK A NORTHSHORE SEC 5 BM73.461 3112 COMSTOCK RD
1726.18 21 7128 NORTHSHORE NEIGHBORHOODASSOCIATION INC 4108 PITTSFORD RD RALEIGH NC 27604.3459 3108 COMSTOCK RD
1726.18 31 0220 TRUONG, DIEN NGOC &LOAN THI TRAN 4417 WATERBURY RD RALEIGH NC 27604.3548 LT 26 BLK A NORTHSHORE SEC 5 4417 WATERBURY RD
1726.18 21 9171 REHM, HUBERT H & CHRISTINE M 4413 WATERBURY RD RALEIGH NC 27604.3548 LT 27 BLK A NORTHSHORE SECT 5 4413 WATERBURY RD
1726.18 21 6106 HOLDEN, CHARLES RUDOLPH 4508 RYEGATE DR RALEIGH NC 27604-3538 LOT #23 BLK A NORTHSHORE SECT 3 4508 RYEGATE DR
1726.18 21 5094 KNIGHT, WILLIAM C & ADELINA G 4504 RYEGATE DR RALEIGH NC 27604.3538 LT 22 BLK A NORTHSHORE SEC 3 4504 RYEGATE DR
1726.18 21 9012 THOMPSON, GEORGE E & SHELIA M 4409 WATERBURY RD RALEIGH NC 27604.3548 LT 28 BL A NORTHSHORE SEC 5 BM 1972.2 4409 WATERBURY RD
1726.18 20 6905 TOMLINSON, PAULA V &JOHN D TOMILSON 4500 RYEGATE DR RALEIGH NC 27604.3538 LT 21 BLK A NORTHSHORE SECT 3 4500 RYEGATE DR
1726.18 20 9913 SARGINGER, FRANCIS E JR & PHYLLIS G 4405 WATERBURY RD RALEIGH NC 27604.3548 LT 29 BLK A NORTHSHORE SECT 5 4405 WATERBURY RD
1726.18 20 9813 SCOTT, EDWIN W & SUSAN K 6900 VALLEY RIDGE CT RALEIGH NC 27615.7130 LT 30 BLK A NORTHSHORE SEC 5 4401 WATERBURY RD
1726.18 20 5885 SASNETT, K HAINES & NANCY C 4424 RYEGATE DR RALEIGH NC 27604.3536 LT 20 BLK A NORTHSHORE SECT 1 4424 RYEGATE DR
1726.18 20 5757 TOMLINSON, JOSH W & IDA R 4420 RYEGATE DR RALEIGH NC 27604.3536 LT 19 BLK A NORTHSHORE SEC 1 4420 RYEGATE DR
1726.18 20 9714 WILLIAMS, JAMES FULLER & MARTHA B 4313 WATERBURY RD RALEIGH NC 27604.3546 LT 31 BLK A NORTHSHORE SECT 5 4313 WATERBURY RD
1726.18 20 5647 SHUMATE, MARLENE 4416 RYEGATE DR RALEIGH NC 27604.3536 LT 18 BLK A NORTHSHORE SEC 1 4416 RYEGATE DR
1726.18 20 9615 FINCH, GEORGE C & SYLVIA JEAN 4309 WATERBURY RD RALEIGH NC 27604.3546 LT 32 BLK A NORTHSHORE SEC 5 4309 WATERBURY RD
1726.17 20 4651 RICHARDSON, CHANDLER 0 & CYNTHIA P 4412 RYEGATE DR RALEIGH NC 27604.3536 LT 17 BLK A NORTH SHORE SECT 1 4412 RYEGATE DR
1726.18 20 8574 SIMS, WELFORD M & CAROL C 4305 WATERBURY RD RALEIGH NC 27604.3546 LT 33 BLK A NORTH SHORE SECT 4 4305 WATERBURY RD
1726.17 20 4523 HUTAFF, THOMAS G & KRISTIE R 4408 RYEGATE DR RALEIGH NC 27604.3536 LT 16 BLK A NORHTSHORE SEC 1 4408 RYEGATE DR
1726.18 20 8435 MCCONNELL, GARY D & LISA S 4301 WATERBURY RD RALEIGH NC 27604.3546 LT 34 BLK A NORTHSHORE SC 4 4301 WATERBURY RD
1726.17 20 3485 FINNERTY, WILLIAM EDWARD & NORMA J 4404 RYEGATE DR RALEIGH NC 27604.3536 LT 15 BLK A NORTHSHORE SEC 1 BM 1968-184 4404 RYEGATE DR
1726.17 20 3347 WHAREY, SHERYL SWITZER & PAUL 4400 RYEGATE DR RALEIGH NC 27604.3536 LT 14 BLK A NORTHSHORE SEC 1 4400 RYEGATE DR
1726.18 20 8317 HAYES, YVONNE S &ELIZABETH BUNCH 4217 WATERBURY RD RALEIGH NC 27604-3448 LT 35 BLK A NO SHORE SECT 4 4217 WATERBURY RD
1726.17 20 3228 WHITE, LIDIA A 4320 RYEGATE DR RALEIGH NC 27604-3501 LT 13 BLK A NORTHSHORE SEC 1 BM 1968-184 4320 RYEGATE DR
1726.18 20 8217 MILLER, PATRICIA B 4213 WATERBURY RD RALEIGH NC 27604.3448 LT 36 BLK A NORTHSHORE SEC 4 4213 WATERBURY RD
1726.17 20 2270 BIGGERS, JACK L 4316 RYEGATE DR RALEIGH NC 27604.3501 LT 12 BLK A NORTH SHORE SEC 1 4316 RYEGATE DR
1726.18 20 8108 JONES, DOROTHY F 4209 WATERBURY RD RALEIGH NC 27604.3448 LT 37 BLK A NORTHSHORE SEC 4 4209 WATERBURY RD
1726.17 201193 PURSER, HAUGHTON CHUNN & FUSAKO M 4312 RYEGATE DR RALEIGH NC 27604.3501 LT 11 BLK A NORTHSHORE SECT 1 4312 RYEGATE DR
1726.18 20 7077 SPRISSLER, DANIEL L & CRYSTAL D 109 SOUTH BND KNIGHTDALE NC 27545.9795 LT 38 BLK A NORTHSHORE SEC 4 BM670-323 4205 WATERBURY RD
[fir",`\/file
R.M
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?r

June 29, 2005
Ms. Cyndi Karoly
NCDENR
Division of Water Quality
401/Wetlands Certification Unit
2005 1 206
?. F_- J f...µ r
JUN 39 ?005
DFNR - WAfr'-R QL)Ak.JTf
1650 Mail Service Center WETLANDS ANDS-i0R-MVV'ATF-RBRANCH
Raleigh, NC 27699-1650
RE: Northshore and Brentwood Today Lakes Rehabilitation Project
Raleigh, North Carolina
Dear Ms. Karoly:
Enclosed are two (2) copies of an individual permit application, under Section 404 of the Clean
Water Act (CWA), for the Northshore and Brentwood Today Lakes Rehabilitation Project. The
City of Raleigh contracted HDR Engineering, Inc. of the Carolinas (HDR) to perform a study of
these lakes, prepare alternative recommendations, and coordinate public input on the
rehabilitation of these facilities. This permit application includes this cover letter, ENG Form
4345, associated attachments, permit impact sheets, and a list of property owners as specified in
the application requirements. The application is being submitted for CWA Section 404 permit
approval, CWA Section 401 certification, and Neuse Buffer certification under the Neuse River
Riparian Buffer Rules.
Although this plan and design are conceptual in nature, the impacts are primarily related to the
repair and rehabilitation of the spillways and dams, and the reduction of water level in
Northshore Lake. The design of the spillway structures and the reduction of water levels have
reached the point where an impact estimate can be made. Therefore, the City is submitting this
permit application for your review and feedback in order to gain input and comments that will be
incorporated into the final design and, if needed, permit re-application. Additional design will be
occurring as the project continues, but should not significantly change the impacts discussed
below.
Ms. Cyndi Karoly
June 29, 2005
Page Two
Please contact me at telephone number 890-3931 if I may answer any questions concerning this
application or be of further assistance.
Sincerely,

James K. Leumas, P. E.
Senior Project Engineer
JKL/
Enclosures
cc: Mr. Carl R. Dawson, Jr., P. E.
Mr. H. Daniel Bowden, P. E.
Ms. Veronica L. High, E. I.
Mr. Todd Tugwell
Mr. Ronald A. Geiger, P. E.

June 29, 2005
Mr. Todd Tugwell, Project Manager
U.S. Army Corps of Engineers
Raleigh Regulatory Office
6508 balls ofNeuse Road - Suite 120
Raleigh, NC 27615
RE: Northshore and Brentwood Today Lakes Rehabilitation Project
Raleigh, North Carolina
Dear Mr. Tugwell:
Enclosed is an individual permit application, under Section 404 of the Clean Water Act (CWA),
for the Northshore and Brentwood Today Lakes Rehabilitation Project. The City of Raleigh
contracted HDR f;ngineering, Inc. of the Carolinas (H DR) to perform a study of these lakes,
prepare alternative recommendations, and coordinate public input on the rehabilitation of these
facilities. This permit application includes this cover letter, ENG Form 4345, associated
attachments, permit impact sheets, and a list of property owners as specified in the application
requirements. The application is being submitted for CWA Section 404 permit approval, CWA
Section 401 certification, and Neuse Buffer certification under the Neuse River Riparian Buffer
Rules.
Although this plan and design are conceptual in nature, the impacts are primarily related to the
repair and rehabilitation of the spillways and dams, and the reduction of water level in
Northshore Lake. The design of the spillway structures and the reduction of water levels have
reached the point where an impact estimate can be made. Therefore, the City is submitting this
permit application for your review and feedback in order to gain input and comments that will be
incorporated into the final design and, if needed, permit re-application. Additional design will be
occurring as the project continues, but should not significantly change the impacts discussed
below.
Mr. Todd Tugwell
June 29, 2005
Page Two
Please contact me at telephone number 890-3931 if I may answer any questions concerning this
application or be of further assistance.
Sincerely,

James K. L cumas, 11. E.
Senior Project Engineer
JKL/
Enclosures
cc: Mr. Carl R. Dawson, Jr., P. E.
Mr. H. Daniel Bowden, P. E.
Ms. Veronica L. High, E. I.
Ms. Cyndi Karoly
Mr. Ronald A. Geiger, P. E.
APPLICATION FOR DEPARTMENT OF THE ARMY PERMIT- I OMB APPROVAL NO. 0710-0003
/33 CFR 325/ Expires December 31, 2004
The Public burden for this collection of information is sestimated to average 10 hours per response, although the majority of applications should require
5 hours or less. This includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and
completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of
information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Service Directorate of Information
Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302; and to the Office of Management and Budget,
Paperwork Reduction Project (0710-0003), Washington, DC 20503. Respondents should be aware that notwithstanding any other provision of law,
no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control
number. Please DO NOT RETURN your form to either of those addresses. Completed applications must be submitted to the District Engineer having
jurisdiction over the location of the proposed activity.
PRIVACY ACT STATEMENT
Authorities: Rivers and Harbors Act, Section 10, 33 USC 403; Clean Water Act, Section 404, 33 USC 1344; Marine Protection , Research and
Sanctuaries Act, 33 USC 1413, Section 103. Principal Purpose: Information provided on this form will be used in evaluating the application for a
permit. Routine Uses: This information may be shared with the Department of Justice and other federal, state, and local government agencies.
Submission of requested information is voluntary, however, if information is not provided the permit application cannot be evaluated nor can a permit
be issued.
One set of original drawings or good reproducible copies which show the location and character of the proposed activity must be attached to this
application (see sample drawings and instructions) and be submitted to the District Engineer having jurisdiction over the location of the proposed
activity. An application that is not completed in full will be returned.
1. APPLICATION NO. 12. FIELD OFFICE CODE 13. DATE RECEIVED 14. DATE APPLICATION COMPLETED
(ITEMS BELOW TO RE FILLEO BY APPLICANT)
5. APPLICANT'S NAME 8. AUTHORIZED AGENT'S NAME AND TITLE (an agent is not required)
Carl R. Dawson Jr., PE, Public Works Director
City of Raleigh, Public Works Department
6. APPLICANT'S ADDRESS 9. AGENT'S ADDRESS
City of Raleigh, Public Works Department
PO Box 590 Raleigh, NC 27602-0590
7. APPLICANT'S PHONE NOS. W/AREA CODE 10. AGENT'S PHONE NOS. W/AREA CODE
a. Residence a. Residence
b. Business 919-890-3030 I b. Business
r
1 1 . STATEMENT OF AUTHORIZATION
I hereby authorize, to act in my behalf as my agent in the processing of this application and to
urnish, upon request, supplemental information in support of this permit application.
APPLICANT'S SIGNATURE DATE
NAME, LOCATION AND DESCRIPTION OF PROJECT OR ACTIVITY
12. PROJECT NAME OR TITLE tsceinstrucrions:
Northshore and Brentwood Today Dam and Lake Rehabilitation
13. NAME OF WATERBODY, IF KNOWN G1apiJicableJ 14. PROJECT STREET ADDRESS ritapp+,c,9bicJ
Northshore Lake and Brentwood Today Lake, both on the New Hope
tributary to Marsh Creek
15. LOCATION OF PROJECT
Wake County
COUNTY
North Carolina
STATE
16. OTHER LOCATION DESCRIPTIONS, IF KNOWN, i5ecinstructionsl
Northshore Lake Dam coordinates: Latitude 35 deg. 50 min. 13 sec. / Longitude 78 deg. 35 min. 16 sec.;
Brentwood Today Lake Dam coordinates: Latitude 35 deg. 49 min. 56 sec. / Longitude 78 deg. 35 min. 24 sec.
17. DIRECTIONS TO THE SITE
Take 1-440 Beltline to Capital Boulevard, proceed north on Capital approximately 2 miles to New Hope Church Road, turn left on New Hope
Church, after -1/4-mile you will pass Deana Lane on the right, Northshore Lake is then immediately to your north (right) and Brentwood Today
Lake is to your south (left)
NG FORM 4345, Jul 97 EDITION OF FEB 94 IS OBSOLETE.
18. Nature of Activity Wcc cripnngorpro;%? r,inci„neen;r?ruresi
This activity includes repair and rehabilitation of Northshore and Brentwood Today dams and spillways, dredging of both lakes, and lowering of
the water level in Northshore Lake for flood control. [See attachment]
19. Project Purpose (Describe the reason or purpose or the project, sce mstrudronsi
These two lakes are privately-owned earthen dams with a recent history of overtopping during high flood events. Both dams and spillways are
in need of repair. The lakes are surrounded by residential homes and apartments that are subject to flooding. New Hope Church Road, just
downstream of Northshore Lake, could wash out due to an overtopping event. Both lakes have filled in with sediment over the past several
decades, thereby decreasing water quality. [See attachment]
USE BLOCKS 20-22 IF DREDGED AND/OR FILL MATERIAL IS TO BE DISCHARGED
20. Reason(s) for Discharge
Discharges are mainly related to the repair and rehabilitation of the dams and spillways. Some additional discharges will be associated with the
sediment pool construction and establishment of fringe wetlands around the lakes. [See attachment]
21. Type(s) of Material Being Discharged and the Amount of Each Type in Cubic Yards
[See attachment]
22. Surface Area in Acres of Wetlands or Other Waters Filled (seemstruchons)
[See attachment]
23. Is Any Portion of the Work Already Complete? Yes No X IF YES, DESCRIBE THE COMPLETED WORK
24. Addresses of Adjoining Property Owners, Lessees, Etc., Whose Property Adjoins the Waterbody (If more than can be entered here,
please attach a supplemental list).
See attached list
25. List of Other Certifications or Approvals/Denials Received from other Federal, State or Local Agencies for Work Described in This Application.
AGENCY TYPE APPROVAL' IDENTIFICATION NUMBER DATE APPLIED DATE APPROVED DATE DENIED
'Would include but is not restricted to zoning, building and flood plain permits
26. Application is hereby made for a permit or permits to authorize the work described in this application. I certify that the information in this
application is complete and accurate. I further certify that I possess the authority to undertake the work described herein or am acting as the
duty authorized e o the applicant. d-i (e Z9 6?
SIGNATURE OF APPL ANT DATE SIGNATURE OF AGENT DATE
The application must be signed by the person who desires to undertake the proposed activity (applicant) or it may be signed by a duly
authorized agent if the statement in block 11 has been filled out and signed.
18 U.S.C. Section 1001 provides that: Whoever, in any manner within the jurisdiction of any department or agency of the United States
knowingly and willfully falsifies, conceals, or covers up any trick, scheme, or disguises a material fact or makes any false, fictitious or
fraudulent statements or representations or makes or uses any false writing or document knowing same to contain any false, fictitious or
fraudulent statements or entry, shall be fined not more than $ 10,000 or imprisoned not more than five years or both.
Northshore and Brentwood Today Dam and Lake Rehabilitation
List of Permit Application Attachments
Permit Narrative (with Photographs)
Figures 1-7 (includes Project Vicinity Map)
Preliminary Spillway Drawings (3 figures)
Email Communication with Becky Fox of the USEPA
Technical Memorandum No. 4 (Water Quality Evaluation of Conceptual Plans)
List of Adjacent Property Owners
Northshore and Brentwood Today Dam and Lake Rehabilitation Project
Section 404 Permit and Section 401/Neuse Buffer Certification Narrative
The narrative below is a thorough description of the project. Under each heading, the
corresponding item from ENG Form 4345 is listed in parentheses if applicable. For
continuity and readability reasons, the items are not necessarily in the order they occur in
the permit, and additional items are included for justification of the project.
Project Background and Purpose (Item 19)
There are a series of four lakes along the New Hope tributary to Marsh Creek and
Crabtree Creek: an unnamed lake, Northshore Lake, Brentwood Today Lake, and
Beaman Lake. The dam at Beaman Lake was breached several years ago and
reconstruction was recently completed to restore the dam embankment and install
features to improve water quality, including constructed wetlands.
This Project includes Northshore Lake and Brentwood Today Lake, which are located in
the City of Raleigh (City) near New Hope Church Road and west of U.S. Highway 1
(Capital Blvd.) as shown in Figure 1. The dams at both Lakes were identified as small,
high hazard dams in a report by Titan Atlantic dated July 20, 2004. Furthermore, the
spillways at both Lakes have been a safety concern for over 20 years. The dams have
been overtopped several times in recent years, causing flooding in the surrounding
residential area. There is also concern that New Hope Church Road, located just
downstream of Northshore Dam, has the potential to wash out during an overtopping
event.
In addition to safety concerns, development in the drainage basin over the last several
decades has created a significant amount of runoff and sedimentation entering these
lakes. Both Northshore and Brentwood Today have an estimated 3-5 feet of sediment in
their lower, deeper areas, and are very shallow in the upper ends with less than a foot of
water in some areas. Peninsula wetlands have been created in the headwater regions of
both lakes through accumulation of sediment. Algae and other noxious plants are present
throughout the lakes, but are concentrated in these shallow upper-headwater areas.
In 2004, the City of Raleigh (City) made a commitment to evaluate the potential of
rehabilitating the Northshore Lake and the Brentwood Today Lake dams and spillways to
minimize and/or prevent flooding to the neighboring property owners as well as improve
public safety downstream. The analysis of these two lakes was driven by three primary
objectives:
1) Address NC Dam Safety concerns for long-term stability and downstream
protection
2) Identify opportunities for water quality enhancement of the watershed
supplemental to ongoing City efforts
3) Preserve property value for the neighborhoods surrounding these lakes.
Northshore & Brentwood Today Lakes page 2 of 15
4041401 permit Application Narrative
The underlying goal for this effort is to provide a project that addresses these objectives
while achieving public support and meeting the goals of the City of Raleigh's Storm
Water Program. The planning process provided the basis for conceptual layouts for
rehabilitating the dam structures while also increasing water storage capacities and water
quality benefits. The conceptual layouts, discussed in the alternatives analysis section,
were produced with City input and presented for public comment. This planning process
provided a recommended plan comprising dam safety and water quality benefits. Both
lakes are located within the Marsh Creek watershed, which exhibits serious nutrient-
loading problems. This concept would help to reduce some of this nutrient loading as
discussed below.
Project Description (Item 18)
Although two separate lakes, the recommended improvements to these facilities are being
proposed in conjunction due to the overall purpose of this project. The analysis of
alternatives and development of a recommended plan were performed using a watershed
approach to the water quality issues, while looking individually at the project components
such as each dam and spillway. This plan development included incorporation of the
available flood control capacity of Northshore Lake, and the water quality improvements
of Beaman Lake to yield an overall approach for the New Hope tributary watershed.
Northshore Lake (Figure 2)
The Northshore Lake recommended plan is focused on long-term aquatic habitat
and nutrient-removal improvements, in addition to the required dam safety
improvements. An approximate 0.8-acre sediment pool is proposed to be located
just south of Comstock Road within the old Northshore Marina lot and an
adjacent parcel that currently contains a residential structure. The house is
located within the 100-year floodplain and is considered a hazard for flooding.
The sediment pool would require periodic maintenance in order to remove the
sediment build-up. Upland areas around the sediment pool would be set aside for
maintenance access and storage. The pool will serve the same function that the
lake has been providing by trapping sediment, but this will limit the area requiring
maintenance and increase accessibility.
Normal pool elevation would be dropped 2.5 feet to a normal pool elevation of
262 feet in order to provide additional flood storage without raising the dam and
impacting adjacent landowners. The proposed spillway structure is a notched
drop-chute spillway that would incorporate a 25-foot-wide weir at an elevation of
263'. In order to pass high flows, a 150-foot weir length would be constructed at
an elevation of 265.9'. To minimize impacts to the dam, the structure will
protrude into the lake. The hardened channel below the weir would slope from an
invert elevation of 261' down to 256', where it would then tie into the existing
channel below the dam. In addition, several 2" water-quality drawdown holes
using orifice plates at an elevation of 262' will be included in the spillway. These
holes will reduce clogging and will pass the daily flow in addition to any
floodwaters stored between 262' and 263'. Flood storage capacity would be
Northsliore do Brentwood Today Lakes
4041301 Permit Application Narrative
Page 3 of 15
increased by 1.5 vertical feet with an additional 1-foot drawdown for water
quality improvement purposes.
Approximately 1.5 acres of the lake would be dredged to remove much of the
depositional sediment that has accumulated over the 50+-year life of the lake.
Using existing bathymetry as a guide, the dredging would occur in the upper
portions of the lake and around parts of the lake perimeter. The dredging would
also be performed in order to keep the lake surface area approximately equal to
current conditions. Since some of the existing wetlands may be drained due to the
drop in water elevation, planting of created headwater wetland areas may occur to
enhance their development. An approximate 0.7-acre headwater wetland would
be created below the sediment pool to help filter out nutrients and contaminants
prior to reaching the lake. This headwater wetland will be planted with trees and
constructed such that shallow channels braid through the system. Small plunge
pools are proposed where existing point-source pipes and channels discharge
directly into the lake. These would provide some treatment for sediment and
contaminant runoff from the stormwater outfalls.
Brentwood Today Lake (Figure 3)
The Brentwood plan would provide primarily for spillway replacement and lake
bathymetry restoration. The existing spillway structure has been progressively
failing over a period of years and needs to be addressed relatively soon in order to
prevent a complete failure of the spillway (a failure of this magnitude may result
in an outflow that could adversely impact downstream lives and property in
addition to the aforementioned Beaman Lake reconstruction project). The
proposed structure would have a 100-foot weir length at an elevation of 245.2'
with a 20-foot notch cut down to 242'. The channel invert below the weir would
be 238', sloping down on a 1-percent grade to an energy-dissipating structure at
the confluence with the existing stream channel. No change in water level is
proposed for this lake since it would add only a minor amount of additional flood
storage.
Approximately 3 acres of lakebed would be dredged. A 0.4-acre sediment pool
would be created where an eastern tributary enters the lake. A plunge pool along
the western shoreline and a sediment pool below New Hope Church Road are also
proposed in this plan. Other than the minor wetland impact from the eastern
sediment pool, the wetlands on-site are to be preserved in order to provide water
quality and habitat benefits.
Alternatives Analysis
The attached technical memoranda describe the Concept Plans shown in Figures 2
through 3, along with the analysis used in the evaluation of these alternatives. In general,
three alternatives were evaluated for each lake:
¦ Dam safety and flood attenuation,
Nonhslmre & Brentwood Today Lakes
4041401 Permit Appliration Narrative
¦ Water quality improvements, and
Page 4 of 1s
¦ A composite plan integrating dam safety and water quality (Recommended Plan).
The dam safety recommendations were integrated into all three alternative scenarios,
since exclusion of these recommendations was not practical due to public safety
concerns. Therefore, a "no action alternative" was not considered for permitting
purposes for this project.
The analysis, fully documented in the attached technical memoranda, resulted in the
recommendation of the plan described above. This plan included the required elements
for dam safety and flood attenuation, and incorporated both water quality elements and
public interests. The resulting project yields an increase in water quality efficiency of the
facilities, while satisfying to the greatest practical extent the needs and interests of the
adjacent landowners.
Project Impacts, Minimization, and Avoidance (Items 20, 21, 22)
The impacts of the proposed project on each type of jurisdictional area are presented in
Table 1 and discussed by site below. Along with each impact description is a discussion
of the minimization and avoidance performed at each site. Overall, impacts are mostly
limited to the original footprint of the lakes and spillways prior to the sedimentation and
infilling that has occurred over their 50+-year existence. Stream and wetland delineation
was performed in April-May 2004, and field-verified by Ms. Jennifer Burdette on July
13, 2004 (existing conditions are shown in Figures 4a, 4b, 5a, and 5b; proposed
conditions with impacts in Figures 6a, 6b, 7a, and 7b).
Table 1: Impact Summarv
Site
Number Lake Open
Water ac Forested Wetland
Impact ac Fringe
Wetlands ac Stream
Channel U.
1 Northshore 0.51 0.46 - 260
2 Northshore - - 0.03 -
3 Northshore 0.08 - - -
4 Brenrivood Today - 0.07 - 80
5 Brenrivood Today 0.04 - - 50
Totals 0.63 0.53 0.03 390
Site 1 - Northshore Headwaters:
0.46 acres of riparian forested wetlands will be impacted in this area due to the
drop in the normal pool elevation of the lake (Figure 6a). This will eliminate the
hydrologic conditions necessary for the survival and propagation of the wetland
species currently present. In addition, over time the hydric soil characteristics of
this area will be eliminated and the area will likely revert to an upland riparian
system. 0.51 acres of pond will be converted to wetland due to the reduction in
water levels. This area will be planted with riparian wetland vegetation in order
to enhance the water quality benefits of the project and replace the habitat lost in
the draining of the current wetland areas. Approximately 0.18 acres of the 0.46
Northshore & BrenAvood Today Lakes
4041401 Permit Application Narrative
Page S of 15
acres of wetlands will also be excavated to allow for the construction of a 0.8 acre
sediment pool or forebay within the original footprint of the lake. This forebay
will be used to minimize the amount of maintenance required in the future and
limit this activity to an easily accessible area. The forebay construction will
impact an additional 260 linear feet of perennial stream channel that is currently
inundated by the lake.
Avoidance of this impact was not practical due to the heavy historical and current
sediment load that has led to the conditions described above. An off-line
sediment pool or forebay was considered for this location in order to avoid
impacting the current stream channel and wetlands. This would have divided the
forebay into two sections on either side of the stream and greatly reduced the
volume of water controlled. In addition, normal base flows would have been
passed by the stream without contact with the sediment pools. Since the entire
lake is currently acting as a sediment pool for the upstream drainage, it was
determined that an in-line forebay was the most practical option.
Draining of the current wetland areas was examined to determine if there were
options to avoid this impact. However, since flood control is a primary concern
below the dam, the water level has been decreased in the Recommended Plan to
provide additional flood storage and spillway capacity, which brings the dam's
spillway capacity into compliance with the NC Dam Safety Act. Since the flood
control storage drop of 1.5 feet is necessary and would drain the wetlands at the
site, it was determined that an additional 1 foot of water drop would be beneficial
for water quality purposes and would not cause additional impacts to the
wetlands. Alternative flood control strategies, such as raising the existing dam
elevation, were considered but found to not be practical due to the potential
impacts on adjacent landowners.
Site 2 - Northshore Fringe Wetlands
0.03 acres of current fringe wetlands are located around Northshore Lake as
shown in Figures 4a and 4b. These wetlands have formed in the flatter portions of
the lake margin where water is shallow enough to allow colonization by
hydrophytic plants. Lowering the water level will impact all of these wetlands.
The dredging of the lake will maintain the current lake margins by creating a
shallow shelf along the edge of the lake. Fringe wetlands are likely to reform in
areas that supply suitable depth.
As stated above, avoidance of the water level decrease was examined but deemed
not practical due to flood control and spillway capacity issues necessary to
comply with the NC Dam Safety Act. Therefore, the impacts to the fringe
wetlands are necessary. Minimization of these impacts is being achieved through
the dredging of adjacent shallow waters to maintain the current lake banks and
create shelves along the shore. This will allow for the natural reestablishment of
fringe wetlands in suitable locations around the perimeter of the lake.
Northshore do Brentwood Today Lakes
4041401 Permit Application Narrative
Site 3 - Northshore Dam and Spillway
Page 6of15
The construction of the Northshore spillway device, shown in Figure 6b, will
impact approximately 0.08 acres of open waters. No additional stream channel
will be impacted by the rehabilitation of the existing spillway downstream of the
dam. This stream channel is currently concrete and rock lined. This material will
be removed and replaced with proper materials. During construction, the stream
will be diverted around the current channel through pipes, preferably via gravity
flow.
Avoidance of this impact was deemed impractical due to the high flood hazard
conditions, the current state of the spillway, and lack of compliance with the NC
Dam Safety Act. The enlarged weir will remove some open water, but is
necessary to control the flows entering the spillway and reduce downstream
velocities and flooding potential. The current spillway is cracked and a portion of
the base flow is bypassing the spillway through voids underneath. This would
eventually lead to the failure of the spillway and degradation of the downstream
channel. The spillway length has been limited to not cause additional impacts to
the stream channel. The leveling of the dam will not impact the stream or open
water.
Site 4 - Brentwood Today Eastern Tributary
Although sediment is being controlled along the main stem lakes and stream
through the sediment pool on Northshore Lake, there is a significant amount of
the overall watershed (31%) that enters Brentwood Today Lake through an
eastern tributary that is piped under the Mini-City area along Capital Boulevard.
The sediment load in this tributary has created headwater wetlands similar to
those at the upper end of both lakes. In order to reduce this sediment load and
minimize further filling of the Brentwood Today Lake, a sediment pool is
proposed on this tributary. Construction of this pool will impact 0.07 acres of this
wetland area. The remaining wetland and the wetlands at the upper end of the
lake will not be impacted. In addition, 80 feet of perennial stream channel of the
eastern tributary will be impacted by construction of the sediment pool (Figure
7b).
Avoidance of this impact was considered, but it was not deemed practical due to
the sediment load currently produced from the watershed to the east of Brentwood
Today. As discussed above, an offline forebay would not control base flow
sediment load and would be greatly reduced in size. In addition, it would likely
involve additional taking of properties.
Site 5 - Brentwood Today Dam and Spillway
The 50 feet of remaining spillway at the Brentwood Today Lake is progressively
collapsing and the banks of the stream channel are sloughing in. The original
spillway length below the dam was approximately 200 feet. The proposed
spillway length is 100 feet, which yields an additional impact of 50 linear feet of
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Page 7 of 15
perennial stream channel when compared to current conditions, but is within the
original footprint of the 200' spillway. The current conditions of this stream
channel, and the impending failure of the remaining 50 feet of the spillway,
prevent any other alternative solution besides draining the lake. The inlet
structure will impact an additional 0.04 acres of open waters.
Avoidance of the spillway improvements was unavoidable due to the state of the
current structure. Of the original 200 foot spillway, only 50 feet remain (and
sections are continuing to collapse). The proposed length of the spillway is
enough to pass the required flows (based on Dam Safety Act requirements) and
tie into the existing stream channel while reducing velocities of the outflow so as
to minimize potential for downstream degradation.
Mitigation
The original concept for compensatory mitigation for this project was to use the enhanced
wetlands associated with the Northshore Lake (Figures 6a and 6b) to offset the
unavoidable wetland losses. In an October 5, 2004 pre-application meeting with the
USACE, it was determined that these wetlands could not be used as compensatory
mitigation since they are a component of a stormwater facility. This was concurred by
the EPA in email correspondence on February 7, 2005. It was agreed in the pre-
application meeting with the USACE that a proposal would be considered to not require
mitigation for impacts if functional replacement could be proven for the project. DWQ
401 Certification Unit staff tentatively agreed to a similar approach in an October 22,
2004 pre-application meeting. Therefore, the following mitigation section is designed to
justify the waving of compensatory mitigation for the proposed impacts due to the
functional replacement of the project components.
Wetland Functions
The impacted wetlands are discussed below by category of wetland functions as
described in the "Guidance for Rating the Values of Wetlands in North Carolina"
published by NCDENR.
Dater Storaze
The current wetland areas consist of bars of sediment transported downstream and
deposited at the inlet of the lakes. Little microtopographic relief is present in
these wetlands and therefore their water storage capacity during flood events is
low. As these wetlands have formed above the normal pool elevation of the lakes,
they have actually decreased the amount of flood storage provided by the
freeboard of the lakes. The increase in flood storage capacity created by the drop
in water level of Northshore Lake will greatly increase flood storage capacity of
the entire system and therefore offset any loss of flood storage retention in the
wetland areas.
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Bank/Shoreline Stabilization
Page 8 qF 15
The current wetlands consist of fine silts and sands deposited in the upper end of
the lakes. These areas are constantly shifting and provide little stabilization of the
stream banks. Vegetation in much of these areas is limited to herbaceous species
such as Jewelweed (Impatiens capensis) that provide little stabilization.
Reduction of the water level in Northshore, along with the dredging of sediments
in both lakes, will remove most of these sediments. The creation of the sediment
pools prior to these wetland areas will help to reduce the erosive velocities and
scour potential of the streams and therefore will not decrease the bank
stabilization of the system. Currently, the stream channels immediately upstream
of the open water are pooled, channelized, and relatively incised. The channel
below the Brentwood Today dam is currently caving in and causing additional
water quality problems. Overall, the project will reduce downstream erosion
potential by controlling flooding and reducing velocities downstream of the
spillways. This reduction in erosion and stabilization of the currently eroding
banks adjacent to the spillway will help mitigate the minor stream impacts
associated with the project. The current conditions of the streams, specifically the
stream below Brentwood Today, would more than mitigate for the loss of this
function.
Pollutant Removal
The current wetlands do provide some pollutant removal for the incoming flows.
However, as described in the following text and supported in the attached
technical memoranda, pollutant removal efficiencies will be increased throughout
the watershed as a result of this project. This was one of the primary purposes of
this project.
Examination of the New Hope Tributary (including Northshore and Brentwood
Today Lakes) as the system of treatment facilities for the entire watershed
provides a comprehensive assessment of water quality. Table 2 integrates the
combined loadings from all five sub-watersheds studied (attached as Technical
Memorandum No. 4) and the trapping capacity of both lakes to yield a composite
load and overall removal efficiency from the system. These results are presented
in the last three columns of Table 2. The system is operating in the mid-range of
the removal efficiency for wet ponds, based on the initial assumptions of poor
removal capacity for the individual lakes. However, the main function of this
system simply operates to detain pollutants and does not facilitate the expedition
of these pollutants entirely out of the system. Nitrogen, phosphorus, and TSS
would be available for reintroduction into the system's downstream conveyance.
Northshore do Qrcnttirood Today Lakes
4041401 Permit Application Narrative
Tahle 2: Comnarative Loading Analvsis
Page 9 of 15
Loadings to Total Loadings to Trapped Load from Loadings out of Overall
Constituent Beaman Brentwood &
the System
Brentwood Removal
Lake * Northshore Efficiency
Total Nitrogen 3,872 13,320 4,124 9,196 31%
Total Phosphorus 1,215 1,400 787 613 56%
TSS 284,712 285,050 226,648 58,402 80%
Fecal Coliform N/A 4,540 850 3,690 19%
NOTES: Loadings are presented in Ibs/year except for fecal coliform, ti,ihich are presented in colony forming units x
10''/year; '- Data from Beaman Lake Embankment Rehabilitation report.
The initial assessment of total nitrogen removed by Northshore and Brentwood
appears to meet the 30 percent reduction requirement in nitrogen specified in the
Neuse River Rules. However, the City of Raleigh's Stormwater Management
Design Manual requires that the nitrogen load from new development not exceed
3.6 Ibs/acre/year. This equates to approximately 2,700 lbs/year, which would
theoretically be the target loading out of Brentwood Lake if the two watersheds
were not already mostly built-out. This is a much smaller loading as compared to
the present loading of approximately 9,200 lbs/year out of Brentwood Today.
While the 2,700 lbs/year may not be a reasonable goal, it still emphasizes the need
for maximizing nitrogen control where possible.
Wildlife Habitat
The current wetlands are relatively small and provide little wildlife habitat. The
vegetation primarily consists of herbaceous species, with some younger saplings,
shrubs, and trees. The surrounding land use is almost completely built out and
provides little refuge for populations of wildlife. Potential cover is adequate only
in spotty areas, and is periodically cleared out by adjacent landowners. Mast
producing trees and other food sources are limited by this disturbance. The
project will remove some of the thin riparian buffer along the streams and lakes in
the area of the sediment pools. This will be mitigated by the replacement of
similar vegetation types and cover in the enhanced wetlands created by the
exposure of additional land surface when the Northshore Lake level is dropped.
Additional open water created by the dredging operations, along with the
establishment of littoral shelves and benches around the perimeter of Northshore
Lake will increase waterfowl habitat.
Aquatic Life
Currently, the aquatic habitat of the two lakes and connecting streams is in poor
condition. As described above, the lakes have gradually filled in with sediment
and therefore removed most of the deepwater habitat in these systems.
Approximately 30% of Northshore Lake and 50% of Brentwood Today are less
than 1 foot deep. This has created conditions that promote the growth of algae
and invasive aquatic plants that are currently choking the system. The dredging
of the lakes and control of the sediment load coming downstream will greatly
enhance the aquatic habitat of the lakes. The lowering of the Northshore water
level will allow the stream below Comstock Road to flow rather than be
Nortluhore & Brentwood Today Lakes
4041401 Permit Application Narrative
Page 10 of 15
inundated most of the time. Based on interviews with local residents, fish
populations in both lakes have seriously declined in the last several decades. The
aquatic benches created by the dredging operations will add aquatic habitat by
providing shallow water refuge adjacent to deeper water habitat. The construction
of the spillways will not change the current impediments to fish passage. The
overall project will improve the quality of the aquatic habitat in both the lakes.
Recreation and Education
Recreation opportunities, which were originally quite high for these lakes, have
drastically decreased over the last several decades. Fishing has declined due to
the decrease in fish populations associated with the poor water quality and
sedimentation. Boating opportunities have also declined as significant portions of
these lakes have become inaccessible by watercraft. Several docks are currently
surrounded by wetlands or water less than 1 foot deep. The project will increase
both these functions to a great extent. Fish habitat will be increased, and over
time fishing opportunities should likewise increase. Boat access will be enhanced
through the dredging of the lakes. While some areas without current open water
access will not change (such as the upper portion of Brentwood Today),
landowners with access to open water will have that access enhanced through the
dredging of channels and deepening of the lakes.
Stream Mitigation
Stream impacts associated with this project are limited to 390 linear feet of
perennial stream. Current stream channel degradation along the old spillway of
Brentwood Today Lake will be repaired during the construction of the spillway,
and downstream impacts from sedimentation and erosive velocities will be
reduced by the proposed enhancements and rehabilitation. Since the stream
channels along the spillways of these lakes have already been impacted, only
additional stream channel impacts have been included in these calculations. Any
channel impacts occurring at the upper reaches of each lake are impacting open
water that falls within the streambanks - these channels are not functioning as
streams but as open water conveyances. Some grade control points may be
established in the exposed stream channels to prevent head cutting as needed.
Therefore, no stream mitigation is being proposed for this project. The overall
watershed and water quality improvements associated with this project provide
sufficient mitigation for the minor amounts of stream impacts.
Based on the overall assessment of the functions described above, each wetland
function is at minimum replaced and, more frequently, enhanced by the project.
Stream impacts and enhancements are largely offset by the primary goal of water
quality improvements and the rehabilitation of the dams. The overall goals of
flood control and water quality, along with the current severely degraded state of
these lakes, provides mitigation for these functions through an alternative delivery
process rather than traditional compensatory mitigation. It is therefore proposed
that no formal compensatory mitigation be required for the impacts associated
with this project.
Northshore do Brentwood Today Lakes
4041401 Permit Application Narrative
Neuse Buffer Impacts and Mitigation Requirements
Page 11 of 15
Figures 6a, 6b, 7a, and 7b present the current riparian buffers within the project area
under jurisdiction of the Neuse River Riparian Buffer Rules. The proposed plan will
impact 1.95 acres of the total 12 acres of buffers currently surrounding the lakes. These
impacts stem primarily from spillway improvements and sediment pool construction.
The impacts related to the rehabilitation of the dams and spillways are exempt under the
current rules. Since the dredging operation will retain the current lake limits by creating
benches along the shores, no permanent loss of riparian buffers are associated with this
activity. The construction of the sediment pools will require impacts to 0.84 acres of
riparian buffers. These impacts do not create new impervious surfaces.
Protected Species
Plants and animals classified as Endangered or Threatened by the U.S. Fish and Wildlife
Service (USFWS) are protected under provisions of Section 7 and Section 9 of the
Endangered Species Act of 1973, as amended. Table 9 presents USFWS list of federally
protected species for Wake County, North Carolina as of February 25, 2003.
Table 3: Federal Listed Protected Species for Wake County. NC
Scientific Name Common Name Federal Status
Haliaeetus leucocephalus Bald eagle Threatened-Proposed
for Delistin
Picoides borealis Red-cockaded woodpecker (RCW) Endangered
Alasmidonta heterodon Dwarf wed emussel Endangered
Rhus mlchatoci Michaux's sumac Endangered
Limited potential habitat exists on-site for each species (Bald eagle - open water; RCW -
mature pines; Dwarf wedgemussel - perennial streams; Michaux's sumac - regularly
maintained edge habitat). Prior to construction, surveys will be performed for each
species as requested by the permitting agencies.
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Photographs
k.
Page 12 of 15
t
Upper end of Northshore Lake
Upstream end of Northshore Lake, looking upstream near Comstock Road
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative

Page 13 of 15
Northshore Lake, looking upstream from the dam
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
??
Page 14 of 15
?I
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Brentwood Today dam spillway, looking downstream from the top of the spillway (as of
September 2004)
Brentwood Today Lake, looking upstream from the dam
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Page /5 of /5
Post-storm destruction below Brentwood Today spillway due to bank erosion and sloughing
(April 2004, along the eastern streambank and -20' downstream of existing spillway)
Approximate former location of Brentwood Today spillway, now -150 feet downstream of
the progressively collapsing end of the spillway seen above
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Jamison, John R.
From: [e-mail]
Sent: Monday, February 07, 2005 3:00 PM
To: May, Philip
Cc: [e-mail]
Subject: RE: Forebay Issues
Phil,
Just wanted to send you a quick reply to your forebay question before I head out on work
travel. It is my opinion that the forebays will not be an issue if the permit decision is
made to convert these ponds to stormwater treatment systems and appropriate mitigation is
provided for this loss of "waters" since they will no longer be jurisdictional waters of
the US. I also spoke to EPA's regional stormwater expert and she concurred with this. We
would caution that the forebays should not be constructed to a depth as to allow them to
become anoxic and/or to thermally stratify. It appears this is not the case with your
design which indicates forebays will be constructed 2 to 4 feet in depth. Most literature
recommends an average depth of wet ponds to be in the range of 3 to 9 feet. If you are
wanting to go deeper than that we would like to further discuss this with you. We would
recommend that you might want to make your forebays a little deeper than you are proposing
to allow for some accumulation of coarse material between scheduled maintenance. This
would help prevent resuspension of particulates during larger events.
One concern I did have when I reviewed your website is that it appears you are proposing
wetlands between the forebay and the larger pond to be used as mitigation for project
impacts. This is something we would want to discuss with you and Jennifer since it is our
position that mitigation credit can not be given for an area that is not jurisdictional
which would apply to these ponds if they are converted to storm water treatment systems.
Shallow wetland shelves are an important component of a good pond treatment system so we
would encourage their construction but can not recommend they be used to provide
mitigation credit.
Let me know if I can be of any more assistance.
getting back to you on the forebay issue.
Once again, sorry for the delay in
Becky Fox
Wetland Regulatory Section
USEPA
Phone: [phone]
Email: [e-mail]
"May, Philip" <[e-mail]> wrote on 01/24/2005 03:08:59 PM:
> Thanks Becky - I understand how your schedule must be - especially
around the
> holidays.
> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]]
> Sent: Monday, January 24, 2005 3:00 PM
> To: May, Philip
> Subject: RE: Forebay Issues
> Thanks for the reminder Phil. Things have been crazy since we
communicated
> in Nov and I have not been to Raleigh since then but this project has
been
> floating about in the back recesses of my mind and I knew that I owed
you
> some comments. I will try to get back with you sometime either this
week or
> early next week.
1
> Becky Fox
> Wetland Regulatory Section
> USEPA
> Phone: [phone]
> Email: [e-mail]
> "May, Philip"
> <Phil.May@hdrinc. To: Rebecca
> Fox/R4/USEPA/US@EPA
> com> cc:
> Subject: RE: Forebay
Issues
> 01/24/2005 02:33
> PM
> Becky
> I just wanted to let you know that the City is asking us to prepare
and
> submit our permit prior to our last meeting with the public. If you
have any
> comments on the forebay issue in the next couple of weeks, please let
me
> know. Otherwise, we should be submitting the IP in mid-February and
will
> respond to any comments during the review of the permit.
> Thanks
> Phil
> -----Original Message-----
> From: May, Philip
> Sent: Monday, November 29, 2004 11:32 AM
> To: '[e-mail]'
> Subject: RE: Forebay Issues
> Becky,
> The forebays are planned for the upstream portions of the ponds, which
have
> filled in over the last couple of decades. There are existing
wetlands in
> these areas, however the planned change in water level (to alleviate
flooding
> below the dam by increasing flood storage) would likely drain these
areas.
> We have a web site for the project - www.raleighlakes.com - this has a
> summary of the information provided in a couple of public meetings.
The web
> site is probably the easiest way to get you information - it has a
couple of
2
> powerpoint presentations used in the first community meetings (click
on "more
> information" at each of the community meetings). If you need any more
> information please let me know.
> At this point we have come up with three alternative plans for each of
the
> two lakes and proposed one of each as the recommended plan, but we
would like
> to incorporate all the regulatory input we can get prior to a last
public
> meeting on the final recommended plan. I would like to know the
feasibility
> of using forebays on the project prior to that. I doubt this meeting
will
> happen before January.
> Please call me at your convenience if you have any questions or need
me to
> send you more information.
> Thanks
> Phil
> -----Original Message-----
> From: [e-mail] (mailto:[e-mail]]
> Sent: Monday, November 29, 2004 10:05 AM
> To: May, Philip
> Subject: Re: Forebay Issues
> Phil,
> Will the forebays be constructed in the upstream portion of the ponds
to be
> rehabilitated or will the forebays be constructed upstream of the
current
> dams? If you could send me some info that would be great. You could
send
> smaller files (without pictures and maps electronically) or mail
larger files
> to:
> 1349 Firefly Road
> Whittier, NC 28789
> After reviewing the info I will contact you about either meeting or
phone
> conference to further discuss the projects. What is your time frame?
> Thanks,
> Becky Fox
> Wetland Regulatory Section
> USEPA
> Phone: [phone]
> Email: [e-mail]
> "May, Philip"
> <Phil.May@hdrinc. To: Rebecca
> Fox/R4/USEPA/US@EPA
> com> cc:
> Subject: Forebay
3
Issues
> 11/29/2004 09:49
> AM
> Becky,
> On John Dorney's advice, I am contacting you in regard to the use of
forebays
> on a project involving the rehabilitation of a couple of dams on small
ponds
> in the City of Raleigh. The City is studying these lakes with the
intention
> of repairing the dams or spillways, and adjusting the water levels
(with some
> dredging) to provide additional flood storage and water quality
improvements.
> As a part of the plan we are developing, we have included the use of
deep
> pools or forebays at the upper end of these lakes. I was hesitant to
include
> this and warned our engineers and the City that in-line forebays could
be an
> issues, but the Corps (Jennifer Burdette) said that in conversations
with you
> the forebay issue was not really a problem since the entire lake would
serve
> a stormwater function. John Dorney's take on this is different and he
> therefore recommended we discuss this directly with you.
> I would be happy to send you some information to review. We would
also like
> to meet with you when it is convenient to discuss the project. Do you
have
> any time on upcoming trips to Raleigh to meet?
> Thanks
> Phil
> Philip May
> HDR Engineering, Inc. of the Carolinas
> 3733 National Drive, Suite 207
> Raleigh, NC 27612
> [phone]
> [e-mail]
4
TECHNICAL MEMORANDUM NO. 4
Water Quality Evaluation of Conceptual Plans
NORTHSHORE LAKE AND
BRENTWOOD TODAY LAKE
DAM REHABILITATION PROJECTS
CITY OF RALEIGH, NORTH CAROLINA
February 22, 2005
Prepared By:

HDR Engineering, Inc. ofthe Carolinas
HDR Project No. 10913-9154
TABLE OF CONTENTS
SECTION
PAGE.
1.0 INTRODUCTION ............................................................................................................................1
1.1 Overall Project Description ..................................................................................................1
1.2 Water Quality Component ...................................................................................................1
1.3 Preliminary Water Quality Assessment Methodology ........................................................2
2.0 WATER QUALITY EVALUATION AND MODELING ...........................................................3
2.1 Purpose .................................................................................................................................3
2.2 Model Selection ...................................................................................................................3
3.0 MODEL DEVELOPMENT ............................................................................................................ 5
3.1 Future Land Use Analysis .................................................................................................... 5
3.2 Watershed Delineation ......................................................................................................... 5
3.3 Hydrologic Parameters ......................................................................................................... 6
3.4 Water Quality Parameters .................................................................................................... 7
3.5 Device Parameters ............................................................................................................... 8
3.6 Meteorological Data ............................................................................................................. 8
3.7 Calibration ............................................................................................................................ 9
4.0 MODEL EXECUTION ....................................................................................................................9
4.1 Alternatives Development ...................................................................................................9
4.2 Results and Findings ..........................................................................................................13
5.0 MODEL EVALUATION ...............................................................................................................18
5.1 Continuity Errors ................................................................................................................18
5.2 Sensitivity Analysis ............................................................................................................18
6.0 CONCLUSION AND DISCUSSION ...........................................................................................19
7.0 REFERENCES ...............................................................................................................................21
LIST OF TABLES
3-1 Event Mean Concentrations (EMC) for Selected Pollutants ..............................................................8
4-1 Comparison of Pollutant Loadings from the Preliminary Assessment and the Model .................... 13
4-2 Overall TSS Removal Efficiency ("/o) .............................................................................................. 14
4-3 Overall TPP Removal Efficiency (?o) .............................................................................................. 15
4-4 Overall TKN Removal Efficiency (%) ............................................................................................. 16
4-5 TSS Loading (lbs) Discharge out of Brentwood Today Lake .......................................................... 17
4-6 TP Loading (lbs) Discharged out of Brentwood Today Lake .......................................................... 17
4-7 TKN Loading (lbs) Discharged out of Brentwood Today Lake ....................................................... 17
LIST OF FIGURES
1-1 Project Site Location ...........................................................................................................................2
4-1 Graphical Depictions of the Modeled Networks for the Alternatives ..............................................12
4-2 Removal Efficiency (%) for Discrete Particles .................................................................................15
Water Quality Evaluation i February 2005
of Conceptual Plans
SECTION 1.0 - INTRODUCTION
1.1 Overall Project Description
There are a series of four lakes along the New Hope tributary to Marsh and Crabtree Creeks: an
unnamed lake, Northshore, Brentwood Today, and Beaman. The unnamed lake and Beaman are
presently not included within the scope of this Project. The dam at Beaman Lake was breached
several years ago and is currently under reconstruction, restoring the dam embankment and
installing features to improve water quality.
This Project includes Northshore and Brentwood Today Lakes, which are located in the City of
Raleigh (City) near New Hope Church Road and west of U.S. 1 as shown in Figure 1-1. The
dams at both Lakes were identified as small, high hazard dams in the Titan Atlantic Report dated
July 20, 2004. Furthermore, the spillways at both Lakes have been a concern for over 20 years.
The dams have been overtopped several times in recent years, causing flooding in the
surrounding residential area. There is a concern that New Hope Church Road, located just
downstream of Northshore Dam, may wash out during an overtopping event.
The purpose of this project is to evaluate both Northshore and Brentwood Today Lakes for dam
safety concerns and water quality improvements. Three different aspects will be evaluated:
> Dam safety and flood attenuation,
? Water quality improvements, and
? A composite plan integrating dam safety and water quality.
The purpose of this Technical Memorandum (TM) is to provide an evaluation of water quality
for these three alternatives. Additionally, a discussion of the results of this evaluation along with
baseline conditions derived in previous assessments and the differing aspects of the two
approaches will be presented.
1.2 Water Quality Component
Northshore and Brentwood Today Lakes are classified as C Nutrient Sensitive Waters (NSW) by
the North Carolina Division of Water Quality (NCDWQ). Both Lakes have not yet been rated
for their level of support for this designated use. NSW are less likely to assimilate additional
loadings of nutrients, primarily nitrogen and phosphorus, without detrimental effects on the
water quality. The lake's inclusion as NSW is likely due to their watershed being part of the
Lower Neuse River Basin.
Water Quality Evaluation ? February 2005
of Conceptual Plans

I
j?
Mini City
? i (Development)
I
Northshore
i l y
° C
' ? Ae ch4r
Brentwood Today ch,?q

IV Legend Water Bodies Figure 1.1
--- Road Project Site Location
A Wake County CITY OF RALEIGH
Hydrology
City of Raleigh 1
0 1,000 2,000 January 2005 Tl'? HDk E?rghiecriny.lnc.
Feet Sub-watershed Boundaries ` ?? ottheCnrollni6
Northshore and Brentwood Today Lakes have been significantly impacted in the last 20 years.
During this time, the watershed has seen significant commercial and high density residential
development. The most notable commercial development was the construction of "Mini City"
off Capital Boulevard. With this development has come the disturbance of land and an increase
in impervious area throughout the watershed. The increase in impervious surface increases peak
flows during storm events may have resulted in erosion of unstable stream banks. In addition,
stormwater has transported sediment to these Lakes. This is evident by the unconsolidated soil
deposition found in the mouths of the contributing streams to Northshore and Brentwood Today
Lakes. It is also likely that sediment is carrying a host of urban pollutants to these Lakes, such as
nutrients, metals, organic matter, and fecal coliform.
Eutrophication is also apparent in both Northshore and Brentwood Today Lakes. The abundance
of sediments and solids in stormwater, likely transporting nutrients, as well as dissolved nutrients
found in fertilizers typically used in residential areas have also been conveyed to these Lakes.
Their presence in excess quantity has lead to the excessive growth of phytoplankton or floating
algae that is currently seen in the two Lakes. As the excessive algal biomass dies, it consumes
the bulk of dissolved oxygen that supports life Other contributing sources to the eutrophication
include the waterfowl nesting at the Lakes, domestic pet waste, and possible failing sanitary
sewer lines or sewer overflows.
Bacterial contamination of the Northshore and Brentwood Today Lakes is a prominent concern
as these Lakes are sources of recreation for the adjacent property owners. The Lakes are Class C
and therefore should support the designated uses of secondary contact recreation such as boating
and wading. Visual inspection of the area indicates that some sources of bacterial contamination
(i.e., waterfowl excreta) have direct contact with the Lakes. These Lakes are typical of the urban
setting, in that they likely exhibit fecal coliform levels that do not support the C waters
classification.
1.3 Preliminary Water Quality Assessment Methodology
A preliminary water quality assessment was performed early in the project and documented in
Technical Memorandum #2 TVater Quality Assessment (TM #2). The objective of that water
quality assessment was to evaluate the level and location of pollutant stress being delivered to
these Lakes. That assessment assisted in determining suitable design elements and their location
as well as providing a preliminary baseline for design efficiency. The methodology employed
for the analysis utilized literature values of pollutant export coefficients and geographic land use
data to generate loadings for specific sub-watersheds. That cursory view of watershed conditions
was beneficial in determining a more detailed approach to be used in the final water quality
evaluation of the Project alternatives.
Water Quality Evaluation 2 February 2005
of Conceptual Plaits
SECTION 2.0 - WATER QUALITY EVALUATION AND MODELING
2.1 Purpose
The purpose of this effort and TM are to provide an evaluation of several alternatives with
respect to the improvement of water quality downstream and within the Lakes' system. It is
difficult to translate water quality goals (i.e., concentration and removal efficiency) into tangible
water quality benefits due to the high variability of natural processes and the existence of
unaccountable interactions. However, assuming that this variability is inherent and global, a
relative evaluation of alternatives with similar base conditions and processes will yield a similar
relative response in water quality benefit. An evaluation performed through modeling and sound
interpretation of results will provide this relative assessment.
Water quality models can be used for the prediction of loading, transport, and control of
pollutants. The application of a water quality model will expand upon the empirical effort
accomplished in the TM #2 by incorporating representative data with the simulation of the
existing physical processes. The use of a water quality model will further the assessment in the
following ways:
¦ Provide pollutant loading based on studied pollutant development and hydrologic interaction.
¦ Routing and transport of flow and pollutants through continuous water and mass balance.
¦ Simulation of physical pollutant removal processes and their efficiency over varied
flow/volume regimes.
2.2 Model Selection
The type of water quality model required to fulfill the aforementioned objectives lies within the
range of mid-level models. These models compromise the empiricism of the simple methods
and the complexity of detailed models driven by parameter intensive, mechanistic processes
(EPA, 1999). When fully calibrated and inputed with site-specific parameters they can provide
an appropriate means of prediction. Despite limitations on data availability, these models still
provide decision makers the ability to select watershed-level planning solutions based on relative
comparisons. P8-Urban Catchment Model (P8-UCM), developed for IEP, Inc and the
Narragansett Bay Project by William W. Walker, Jr., Ph.D, was selected for this application
based on these needs. The relative ease of parameter estimation and input and HDR's familiarity
hater Quality Evaluation 3 February 2005
of Conceptual Plans
of the model were factors in its selection. Additional strengths of the model for use in this
Project are listed below (EPA, 1992):
¦ Developed and calibrated for use within small, urban watersheds.
¦ Distributed with particle and water quality pollutant distribution data calibrated against
Nationwide Urban Runoff Program (NURP) data.
¦ Simulation of particle accumulation, decay, and wash-off dynamics.
¦ Sources can be characterized as single, continuous, or diffuse release.
¦ Continuous and storm event simulation.
¦ Provides for the inclusion of several structural Best Management Practices (BMPs): wetland,
detention ponds (dry, wet, and extended), infiltration basins, and swales/buffers.
¦ Hydrologic and water quality output can be evaluated at discrete model components.
¦ Relative evaluation of pollutant loadings, outflow concentrations, and BMP removal
efficiencies.
P8-UCM like many other urban runoff models has some limitations. The following is a brief
listing of limitations of this model (EPA, 1992):
¦ Lack of site specific calibration data limits the model in absolute prediction of pollutants
loads and concentrations.
¦ Primary pollutant removal process is sedimentation and filtration.
¦ Does not simulate in-stream transport and transformation processes for pollutants.
¦ Watershed lag is not simulated.
However, P8-UCM can be a scalable model, in the sense that many of these limitations can be
overcome with site-specific water quality data and representation of physical, chemical, and
biological processes through alternative parameterization.
Water Quality Evaluation 4 February 2005
of Conceptual Plans
SECTION 3.0 - MODEL DEVELOPMENT
3.1 Future Land Use Analysis
A future build-out analysis was performed by Watershed Concepts for the entire Marsh Creek
Basin as part of a hydrologic model. Field inspections of the Northshore and Brentwood Today
Lakes watersheds suggest that current land use conditions are near, if not at, future build-out
conditions. Performing another future build-out analysis with the same base data would yield
similar results. Better value of this analysis would be to evaluate the base data against
orthophotography and field inspections performed while collecting storm sewer inventory. It is
likely that due to the breadth of that previous future build-out analysis and the intent of its end
product, the data was not site checked entirely. With the limited focus of this project the existing
land use and future land use conditions can be individually verified. This is important in
determining hydrologic and water quality parameters for the water quality modeling. The
findings of this evaluation show that the current open space was under estimated by 50 acres.
Much of the land was either characterized as medium residential or industrial. Future build-out
analysis of the open space portion would likely result in some additional commercial land use
but remain mostly open space, as the identified parcels are small and isolated. Due to the small
percentage of mischaracterized land (approximately 6 percent of total watershed area) and its
distribution across the watershed, it is likely this difference will have little effect on
parameterization for this evaluation.
3.2 Watershed Delineation
Watershed delineations were first performed in TM #2 for the purposing of identifying
magnitude and source location of pollutant loads into the Lakes. These same delineations proved
to be sufficient for application in the water quality model and this evaluation. The delineations
were generated using a variety of data detailed below:
¦ City of Raleigh topographic and planimetric CAD data (2000)
¦ NCGIA/DWQ Hydrography (1998)
¦ HDR Storm Sewer Inventory (2004)
P8-UCM emphasizes the location of incoming flows for the proper mixing of flows and
concentrations. Watershed delineations were created to accurately represent the appropriate
routing of flows through existing and proposed water quality controls (sediment pools, wetlands,
Water Quality Evaluation 5 February 2005
of Conceptual Plans
and ponds). The Northshore Lake drainage was delineated into three sub-watersheds called
Upper, Middle, and Lower. The Upper sub-watershed includes the area where the generated
runoff would pass through the smaller unnamed pond south of Calvary Road. The Middle sub-
watershed includes the area where the generated runoff would enter Northshore Lake as a stream
at the mouth of the lake. The final sub-watershed called Lower includes areas draining directly to
the body of Northshore Lake. The Brentwood Today Lake follows the same logic. It is
delineated into two sub-watersheds called Main and Tributary. They represent the areas where
generated stormwater enter the head and body laterally of Brentwood Today Lake and as a side
tributary, respectively.
3.3 Hydrologic Parameters
P8-UCM estimates runoff from precipitation data and hydrologic parameters. The model
evaluates runoff from pervious and impervious areas separately. Runoff for the pervious areas is
computed using the SCS curve number method. These values are adjusted internally based on
antecedent moisture conditions (Haith and Shoemaker, 1987). Since, P8-UCM is mainly applied
in urban settings; this method proves to be a sufficient approach due to its simple
parameterization of pervious conditions that account for only a minor component of the total
urban runoff. The required parameters for pervious runoff generation are SCS curve numbers
representing "open space" land use and respective hydrologic soil groups (SCS, 1986).
Impervious runoff is computed from the difference of cumulative rainfall and depression storage.
Runoff initiates as cumulative rainfall depth exceeds a user-specified depression storage depth.
After this point, runoff equals rainfall intensity for the impervious fraction of the watershed. The
required parameters for impervious runoff generation include depression storage values and
impervious fractions. Depression storage values were obtained from literature values
categorized by land uses (Wright-McLaughin Engineers, 1969) and impervious fractions were
obtained from SCS curve number descriptions (SCS, 1986). The runoff from pervious and
impervious areas is combined and routed to the downstream device with no lag.
The future build-out land use data, described in more detail in Section 3.1 Future Land Use
Analysis, and NRCS digital soil surveys were used to create areas for parameterization. This
hydrologic data was input into P8-UCM for individual land uses within the watershed
delineations. This was done so that future application of the model could be calibrated for
pollutant event mean concentrations if desired. Depression storage and impervious fractions were
input wholly for their respective land use. Only curve numbers for pervious areas were
computed on a composite area average for their hydrologic soil group.
Water Quality Evaluation 6 February 2005
of Conceptual Plans
3.4 Water Quality Parameters
The generation of water quality pollutant loads and runoff concentrations for P8-UCM is based
on the dynamics of particle accumulation and wash-off principles as well as pollutant mass
distribution within those particles. The first component of the quality representation is the
parameterization of particle classes. P8-UCM allows for the distribution of five particle classes.
For each particle class, particle generation parameters are input for both impervious and pervious
segments of a watershed. Impervious input parameters include accumulation rates, decay rates,
wash-off exponents and coefficients, and street sweeping efficiency (when applicable).
Additionally, runoff concentrations can be provided in favor of accumulation and wash-off
dynamics. On the pervious portion of the watershed, particle generation is based on input
parameters of pollutant concentration for the individual particle classes. Particle removal
dynamics are quantified within this component of the P8-UCM model as well. Removal
dynamics are characterized for individual particle classes by settling velocity and filtration
efficiency through pervious mediums.
The second component of the water quality representation within P8-UCM provides for the
distribution of pollutants among the particle classes. Pollutant mass per particle class is the input
parameter. Since multiple pollutants can be modeled with a single particle distribution, scale
factors exist for calibration if desired.
P8-UCM includes several particle distribution data files that can be used for default parameters
when particle and pollutant mass data is not available. The majority of this default data was
calibrated to represent the results obtained in the Nationwide Urban Runoff Program (NURP).
The particle distribution file titled ntttp50.par was used in this evaluation. The file contains five
particles classes that are based on calibration of runoff concentration and settling velocity
distributions representative of median sites (i.e., particle class P10 = 10th percentile). Distribution
of the pollutant mass among particle classes is based upon results of direct runoff concentration,
settling column tests, and typical removal efficiencies of treatment devices (Walker, 1990). This
particle distribution file contains accumulation/wash-off parameters and settling velocities for
four non-dissolved particle classes. The fifth particle class was developed to simulate the non-
settling, dissolved particles. The file also contains mass distributions for a variety of urban
pollutants such as particulates, nutrients, heavy metals, and hydrocarbons. Attention will be
primarily focused on total suspended solids (TSS), total phosphorus (TP), and total Kjeldahl
nitrogen (TKN). Table 3-1 displays the calibrated event mean concentrations per median data
sites of NURP.
Water Quality Evaluation 7 February 2005
of Conceptual Plans
Table 3-1
Event Mead Concentrations (EMC) for Selected Pollutants
Total suspended solids 100.0
Total phosphorus 0.33
Total Kjeldahl nitrogen 1.5
3.5 Device Parameters
Devices provide for the hydraulic routing of runoff and areas for pollutant removal. P8-UCM
utilizes a variety of devices such as an infiltration basin, Swale/buffer, flow splitter, and aquifer;
however, this assessment will only require the use of a detention pond, a general device, and a
pipe/manhole. The detention pond can be used as a device with a permanent pool and a normal
outlet that can be quantified by a single weir and/or collection of orifices. The required input
data for detention pond devices include surface area and volume quantities for permanent and
flood pool levels. The normal outlet that drains only the flood pool requires weir and orifice
dimensions and coefficients. Devices with more complex outlet configurations can be modeled
with the general device which requires a stage-surface area-discharge relationship for its volume
and outlet data. Both these devices also possess a particle removal scale factor. This value is
typically z 1 but can be adjusted higher or lower for the response of the device due to decreases
or increases in hydraulic residence time. The pipe/manhole device is useful for mixing two or
more incoming flows before being routed onto a removal device. Its only input parameter is a
time of concentration and the device provides for no pollutant removal. Pipe/manhole devices
can be used for delaying the hydrologic response of watersheds through the time of concentration
parameter. This approach is beneficial for the modeling of larger watersheds since the watershed
components route runoff with no lag.
3.6 Meteorological Data
Several meteorological parameters are required to balance hydrology for the watershed in P8-
UCM (i.e. precipitation, evapotranspiration, and percolation). Only precipitation and
evapotranspiration require meteorological data. Hydrologic events are driven by hourly
precipitation. Hourly rainfall data monitored at the Raleigh-Durham International Airport was
obtained from the National Climatic Data Center (NCDC) and used with the model. A SCS
Type II distribution (1-inch design storm precipitation file) is distributed with the model package
and also used in this effort. P8-UCM also calculates evapotranspiration using Hamon's Method
from monthly averages of vegetative cover, air temperatures, and hours of daylight (Hamon,
1961). Daylight hours and air temperatures were collected for the area from Summary of the Day
Water Quality Evaluation 8 Febmary 2005
of Conceptual Plans
data also obtained from NCDC. Average monthly values for daylight and temperature were
calculated and inputted. Default data was used for vegetative cover. The total evapotranspiration
calculated by this approach resulted in 29.1 inches/year.
3.7 Calibration
P8-UCM provides for hydrologic and water quality calibration through the use of many
calibration factors and a calibration utility. However, the project watershed and the New Hope
Creek tributary do not have any United States Geological Survey (USGS) gauging stations or
any other confident streamflow monitoring data. A hydrologic and water quality calibration may
not be warranted at this time since the focus of this effort is a relative comparison of alternatives.
However, if the direction of the model is to be a tool for detailed design assessment, collection of
calibration data would be beneficial.
SECTION 4.0 - MODEL EXECUTION
4.1 Alternatives Development
As previously mentioned in Section 1.1 Overall Project Description, this TM will focus on the
water quality benefit gain or loss of the three alternatives: dam safety and flood attenuation,
water quality improvements, and a composite plan integrating the two. Several factors were
considered in the development of these alternatives. Technical Memorandum #3 Conceptual
Plans delivers full detail of the alternatives for each respective lake and the factors for the use of
particular design elements. A summary follows providing representation of each alternative as it
was modeled in P8-UCM. A fourth scenario was developed to represent a situation where
Northshore and Brentwood Today Lakes were breached and return to natural streams.
Dam Safety and Flood Attenuation
The major enhancement to the Lakes for this alternative include dredging, water surface
elevation change (Northshore only), and improved outlet design. These enhancements provide
minor water quality improvement. The new discharge outlets suppress lower design flows thus
increasing hydraulic residence time for particle settling. The dredging of unconsolidated
sediment in the Lake will provide for a net removal of sediment, nutrients, and metals that have
been historically trapped. A net removal of these pollutants will prevent any re-introduction into
the system due to the mixing of high velocity flows with shallow, unconsolidated sediment
layers. The two lake systems were modeled as general devices as opposed to detention ponds due
to their complex weir configuration. The particle removal scale factor was reduced from 1.0 to
Watcr Quality Evaluation 9 February 2005
of Conceptual Plans
0.75 to incorporate the poor distribution of incoming flow at the headwater of the Northshore
Lake and the existence of channelized flow through the Northshore Lake (i.e., short-circuiting).
Removal scale factors less than 1.0 can be assumed to account for poor hydraulic design
(Walker, 1990). Figure 4-1 (on page 12) depicts the model's representation of the system for
this alternative.
Water Quality Enhancements
The water quality improvement alternative utilizes a variety of design elements to ensure the
removal of a variety of pollutants as well as provide additional habitat that would promote the
well being of aquatic life. The improvements for water quality include dredging, water surface
elevation change, improved outlet design, sediment pools, variety of concentrated wetlands,
wetland shelving (Northshore only), and plunge pools for point source runoff discharges. These
improvements attempt to concentrate the settling of the largest particles at the headwaters of the
Lakes where removal of accumulated matter is more manageable. The wetlands are expected to
provide filtration of smaller particles but also promote the biological uptake and trapping of
nutrients. Both Lakes were modeled as a series of detention ponds for the sediment pool and
wetlands. Wetlands were differentiated from the sediment pools primarily by increasing the
particle removal scale factor to 3 to accommodate for additional removal of TSS and TP.
Studies performed using P8-UCM relating detention ponds vegetated with macrophytes to
particle removal factors exhibited scale factors of 2 to 3 for TSS and 3 to 6 for TP to account for
=5 to 30 percent removal (Phillips & Goyen, 1987; Lawrence, 1986). The remaining open water
area of the Lakes was modeled as a separate general device. The wetland shelves and plunge
pools were not included as model elements because they are minor in size and lack definable
continuity with the rest of the system. Figure 4-1 depicts the model's representation of the
system for this alternative.
Recommended
The Recommended alternative combines many of the aspects of the Dam Safety alternative with
some water quality enhancements. Whereas the first two alternatives have specific design
objectives, this alternative considers those objectives in addition to factors such as public
acceptance, constructability, maintainability, and economic value. The design elements for
Northshore are similar to the Water Quality Alternative. However, headwater wetlands exists in
a lower quantity and wetland shelving is limited to plunge pool areas. The volume of dredging
for this alternative is more in line to the Dam Safety alternative. For the Brentwood Today Lake,
the recommended alternative resembles the Dam Safety alternative with the addition of sediment
Water Quality Evaluation 10 February 2005
of Conceptual Plans
pools located at the headwaters of the lake and plunge pools at point source runoff discharges.
Both lake systems were modeled similarly to the Water Quality alternative except with a
reduction in the area of the wetlands at Northshore and exclusion of wetlands at Brentwood
Today Lake. Figure 4-1 depicts the model's representation of the system for this alternative.
No Lakes
The final scenario is a theoretical simulation of the natural drainage system under the future land
use. In this scenario, Northshore and Brentwood Today Lakes are replaced by streams. The No
Lakes scenario provides a baseline of current loadings, concentrations, removal efficiencies as if
the Lakes were never constructed.
Global Model Assumptions
In all alternatives, some general assumptions were made to simplify the assessment. These
assumptions are as follows:
¦ The unnamed lake south of Calvary Drive was conservatively modeled the same in all
alternatives. It was included since its efficiency is important in terms of overall efficiency of
the system.
¦ Stream reaches were modeled as pipe segments with time of concentrations estimated as the
travel time at a bank full event. Pipe segments do not account for any pollutant removal,
which P8-UCM does not have the capacity to model.
¦ Base flow was not simulated since calibration data was not available and land use did not
change from alternative to alternative (i.e., volume of base flow would not change). Base
flow simulation would have yielded minor differences in loadings and removal efficiency
since the particle data file used accounts for 100 percent filtration through the ground in four
of five particle classes and 90 percent for the fifth particle class.
¦ Each alternative was run for a statistically dry, average, and wet year and for the 1-inch Type
II SCS distribution design storm. The statistical years were developed from a 55-year record
of total precipitation values. The statistical wet and dry years were plus or minus one
standard deviation about the average, respectively.
Water Quality Evaluation » February 2005
of Conceptual Plans
DAM SAFETY AND FLOOD ATTENUATION
UPPER MIDDLE TRIBUTARY
NORTHSHORE
UNNAMED BRENTWOOD
TODAY
LOWER MAIN
WATER QUALITY IMPROVEMENTS TRIBUTARY
( MIDDLE UPPER 1
NORTHSHORE
UNNAMED BRENTWOOD
TODAY
LOWER MAIN
RECOMMENDED TRIBUTARY
UPPER MIDDLE
NORTHSHORE
UNNAMED BRENTWOOD
TODAY
LOWER MAIN
ct) 0 o a
WATERSHED DETENTION SEDIMENT WETLAND
POND POOL
Figure 4-1. Graphical depictions of the modeled networks in P8-UCM for the alternatives
Water Quality Evaluation 12 February 2005
of Conceptual Plans
4.2 Results and Findings
Several primary sets of data were retrieved from the model runs for analysis and discussion in
this section. The first set of data summarizes loadings to Northshore and Brentwood Today
Lakes from their respective watersheds. Table 4-1 displays these results and provides a
comparison of previously determined loadings from TM #2. The loadings from P8-UCM model
were developed from accumulation/wash-off dynamics of particle distributions based on NURP
data. Their export mass is a direct result of the interaction with continuous hydrologic events.
The loadings for the preliminary assessment are empirically based on studies relating land use to
storm event concentrations. The P8-UCM-based set of TSS loadings exceeds our previously
determined loadings primarily due to differences in EMCs. EMCs used in the preliminary
assessment ranged from 40-80 mg/L for TSS, while the NURP data supporting P8-UCM had a
TSS EMC of 100 mg/L. EMC's for both assessments were similar for TP and the results
reiterated that similarity. TKN, the predominant particulate form of nitrogen, is modeled in P8-
UCM since the primary removal mechanism of the model is settling. A direct comparison of TN
versus TKN loadings is not valid. However, the values have been provided below as a reference.
Table 4-1
Comparison of Pollutant Loadings from the PreliminaryAssessment and the Model
TSS 168,840 260,691 116,210 207,971
TP 840 833 560 667
TN/TKN 7,300(TN) 3,748(TKN) 6,020(TN) 3,002(TKN)
NOTES: Loadings are presented in Ibs/year. Preliminary loadings for TN only. Final loadings for TKN only.
Tables 4-2, 4-3, and 4-4 summarize the removal efficiency of pollutants for the overall system.
The data included within these tables reflects the relative comparison of the alternatives and a
theoretical simulation of the system with no Northshore and Brentwood Today Lakes. Median
values of pollutant removal efficiency have been referenced from the National Pollutant
Removal Database for Stonnwater Treatment Practices, 2"d Edition developed by the Center for
Watershed Protection and authored by Rebecca Winer. These values provide a baseline for
evaluation; however it must be understood that those median values represent a multitude of sites
under varied design conditions (new construction, retrofit, etc).
Water Quality Evaluation 13 February 2005
of Conceptual Plans
Table 4-2
Overall TSS Removal Efficiency (%)
Average 71 81 76 10
1- Inch Design 62 73 67 9
NOTE: Removal efficiency measured in %.
TSS removal efficiencies ranged from 71 to 81 percent for the average year and 62 to 73 percent
for the 1-inch design storm. Median baseline levels of TSS removal for regional wet detention
ponds and stormwater wetlands are 70 and 80 percent, respectively (Winer, 2000). The Dam
Safety alternative, which contains only wet detention ponds as the main design element, is inline
with this median baseline level. The other alternatives, which include sediment pools and
wetlands, provide only minor increases (z5 percent) on this efficiency and are also in line with
the median baseline level (80 percent). The Recommended and Water Quality alternatives show
improvement in the removal efficiency of the middle two particle classes (P30, P50) as shown in
Figure 4-2. The removal of these particles is directly attributable to the filtering capacity of
wetlands. Dissolved particles (PO) are not significantly removed in any alternative.
Figure 4-2
Removal Efficiency (%) for Discrete Particles
100
90
80
0
>. 70
L)
60
U
50
W
40
E 30
ccc 20
10
0
PO P10 P30 P50 P80
Particle Distribution
- s Dam Safety - * Recommended Water Duality
The preliminary assessment of TM #2 expressed removal efficiency of 80 percent for the overall
system in its current state. The efficiencies selected for Northshore and Brentwood Today Lakes
that culminated in that overall efficiency were likely over estimated; also, that assessment does
Water Quality Evaluation 14 February 2005
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not consider the conservative modeling of the unnamed lake upstream of Northshore Lake,
which reduced overall efficiency in this analysis. Removal efficiencies for the wet and dry year
were within two percent of the efficiency expressed for the average year. The No Lakes scenario
provides minor TSS removal (z10 percent), which is solely attributable to the efficiency of the
unnamed lake.
Table 4-3 displays overall TP removal efficiencies for the alternatives and the No Lakes
scenario. TP removal efficiencies ranged from 38 to 50 percent for the average year and 28 to 40
percent for the 1-inch design storm. Median baseline levels of TP removal for regional wet
detention ponds and stormwater wetlands are 48 and 43 percent, respectively (Winer, 2000). The
Dam Safety alternative, which contains only wet detention ponds as the main design element,
performs below the median level. The other alternatives, which include sediment pools and
wetlands, provide only minor increases (z6 percent) on this efficiency, as expected and are also
in line with the median baseline level (48 percent). The values in Table 4-3 only report TP
removed by settling. It would be expected that as TP breaks down into a non-particulate, bio-
available form (orthophosphorus), nutrient uptake would occur. The nutrient uptake would
improve upon the removal efficiencies displayed in this table for alternatives that include a
wetland. It is difficult to pinpoint the expected removal efficiency attributed to nutrient uptake
as water chemistry and vegetation selection would be major factors in the performance of the
wetland. It could also be expected that during winter months or poor wetland maintenance, that
the wetland would decrease removal efficiency or even be a source of TP.
Table 4-3
Overall TP Removal Efficiency (51c)
Average 38 50 44 4
1- Inch Design 28 40 33 3
NOTE: Removal efficiency measured in °b.
The preliminary assessment of TM #2 expressed removal efficiency of 56 percent for the overall
system in its current state. The efficiencies selected for Northshore and Brentwood Today Lakes
that culminated in that overall efficiency were likely over estimated; also, that assessment does
not consider the conservative modeling of the unnamed lake upstream of Northshore Lake.
Removal efficiencies for the wet and dry year were within 1 percent of the efficiency expressed
for the average year. The No Lakes scenario provides minor TP removal (z4 percent), which is
primarily attributable to the efficiency of the unnamed lake.
Water Quality Evakration 15 February 2005
of Conccptural Plans
Table 4-4 displays overall TKN removal efficiencies for the alternatives and the No Lakes
scenario. TKN removal efficiencies ranged from 33 to 44 percent for the average year and 24 to
36 percent for the 1-inch design storm. Median baseline levels of TN removal for regional wet
detention ponds and stormwater wetlands are 37 and 35 percent, respectively (Winer, 2000).
TKN represents the primarily settleable component of TN. Therefore, it can be roughly assumed
that design elements involving only removal by settling would equate TN and TKN removal
efficiency. The Dam Safety alternative, which contains only wet detention ponds and, therefore,
emphasizes particulate settlement as its primary removal mechanism, performs in line with the
median baseline level for TN. The other alternatives, which include sediment pools and
wetlands, provide only minor increases (z6 percent) on this efficiency. The values in Table 4-4
only report TKN removed by settling. It would be expected that as TKN breaks down and
transforms into non-particulate, bio-available forms, such as ammonium (NH4') and nitrite-
nitrate (NOZ -NO3-) nutrient uptake would occur. The nutrient uptake would improve upon the
removal efficiencies displayed in this Table for alternatives that include a wetland. The median
level of NO, removal in a stormwater wetland versus as wet pond is triple (68 versus 23 percent).
It is difficult to pinpoint the expected removal efficiency attributed to nutrient uptake as water
chemistry and vegetation selection would be major factors in the performance of the wetland. It
could also be expected that during winter months or poor wetland maintenance, that the wetland
would decrease removal efficiency or even be a source of TN/TKN.
Table 4-4
Overall TKN Removal Efficiency (%)
Average 33 44 38 4
1- Inch Design 24 36 29 2
NOTE: Removal efficiency measured in %.
The preliminary assessment of TM #2 expressed removal efficiency for TN of 31 percent for the
overall system in its current state. That estimation was fairly accurate as the TKN removal for
the Dam Safety alternative is within range. Removal efficiencies for the wet and dry year were
within 1 percent of the efficiency expressed for the average year. The No Lakes scenario
provides minor TKN removal (z4 percent), which is primarily attributable to the efficiency of
the unnamed lake.
Tables 4-5, 4-6, and 4-7 summarize the cumulative load entering the stream downstream of
Brentwood Today Lake. Once again, the strength of P8-UCM is not in absolute prediction of
loadings and concentrations; therefore, the alternatives were executed and reported for a
Water Quality Evaluation 16 February 2005
of Conceptual Plans
statistically dry, average, and wet year off rainfall volume. These results demonstrate the range
of loading that could occur under different hydrologic conditions and during a typical design
storm (1-inch SCS Type II distribution). These values may provide reference in determining
downstream impacts.
Table 4-5
TSS Loading (Ibs) discharged out of Brentwood Today Lake
Dry 126,500 86,100 106,500 379,500
Average 137,000 91,200 113,700 421,300
Wet 168,500 113,400 141,100 503,600
1- Inch Design 4,300 3,000 3,700 10,300
NOTE: Loadings measured in lbs.
Table 4-G
TP Loading (Ibs) discharged out of Brentwood Today Lake
Dry 840 680 760 1,390
Average 930 750 840 1,440
Wet 1,120 900 1,020 1,700
1- Inch Design 20 20 20 40
NOTE: Loadings measured in Ibs.
Table 4-7
TICN Loading (lbs) discharged out of Brentwood Today Lake
Dry 4,060 3,390 3,750 5,800
Average 4,530 3,780 4,170 6,500
Wet 5,410 4,530 5,000 7,700
1- Inch Design 130 110 120 160
NOTE: Loadings measured in Ibs.
Water Quality Evaluation 17 February 2005
of Conceptual Plans
SECTION 5.0 - MODEL EVALUATION
5.1 Continuity Errors
P8-UCM performs continuous water-balance and mass-balance checks for single devices and the
entire network. Differences in these checks are identified as continuity errors, which can be
highlighted to the user through the setting of a maximum continuity difference. These continuity
errors are typical of devices with large, rapid fluctuations in volume (e.g., swales/buffers, smaller
detention ponds) (Walker, 1990). Continuity errors can be controlled through a reduced time
step. It was necessary in this modeling effort to run all scenarios with a time step = 8, in order to
reduce continuity errors within the smaller detention ponds representing sediment pools. A
comparison analysis of a particular model run at a time step = 1 and = 8 demonstrated minor
differences in removal efficiency results (less than 1.5 percent). Concentrations and loads
demonstrated slightly higher differences (2 to 6 percent) with the higher end of these differences
occurring in the TSS concentrations.
5.2 Sensitivity Analysis
As previously discussed, P8-UCM and other water quality models exhibit a high level of
variability. Many of the parameters used within this model are based upon estimation and
generalized calibrations; therefore, it is beneficial to understand which of these parameters may
significantly impact the results when not properly quantified. P8-UCM includes a utility that
automates sensitivity analysis for a desired scenario. The sensitivity analysis utility groups input
parameters into four categories: watershed, device, storm, and particle. The parameters for the
first three of these groups are typically user defined and the final group, particle, include default
parameters.
A sensitivity analysis was performed for the water quality scenario since it included the full
range of devices and their parameters. This analysis was run for the average precipitation year
and the variables were increased 25 percent individually. There were two primary observations
from the results of this analysis. Removal efficiencies were less affected than outflow
concentrations by the change in parameters. This reinforces the value of the model as a relative
predictor among scenarios. The second observation showed that the most variable parameters
were in the particle group; a default group of data based on field and laboratory data collected
from a multitude of sites for the NURP program. The parameters demonstrating the highest
variability were the accumulation rate, accumulation decay rate, and wash-off exponent. Their
sensitivity measured as percent change for removal efficiencies and concentrations ranged from
near 0 to 21.6 percent and 3.6 to 24.8 percent, respectively. The high variability in wash-off
Dater Quality Evaluation 18 February 2005
of Conceptual Plans
exponent is due to the exponential response it yields in comparison to linear coefficients
(Walker, 1990). Watershed areas and storm volumes also produced a significant sensitivity as
expected, however they are parameters that can be calculated with confidence.
SECTION 6.0 - CONCLUSION AND DISCUSSION
The purpose of this TM and water quality evaluation was to develop sound input for the relative
evaluation of several proposed alternatives. These alternatives were developed to reestablish or
improve lost functions of Northshore and Brentwood Today Lakes. It was determined that a
modeling effort would provide an objective means of evaluation of these alternatives with
respect to water quality. P8-UCM, an urban runoff model, was selected as a tool that could
objectively evaluate a range of scenarios with limited data. The P8-UCM modeling effort
allowed for the creation of baseline input data, definition of several design elements or BMPs,
and simulation of physical pollutant removal processes. The modeling effort yielded several
sets of data that could be conservatively interpreted into water quality benefits of the varying
alternatives. The water quality benefits are an essential determining factor, but not the only
factor, for the selection and implementation of an alternative for rehabilitation of Northshore and
Brentwood Today Lakes.
Based on this evaluation of pollutant loadings and BMP removal efficiency with results from the
Preliminary Assessment and nationally/regionally expected performance levels the following
conclusions are made:
¦ The use of NURP calibrated particle distribution data allows for the discrete mass
accumulation and removal of particles and their bound pollutants. Regional EMC values
would produce more representative loading but do not provide for accurate removal
efficiency development. Removal efficiency development was a goal of this effort.
¦ Overall pollutant removal efficiencies for TSS did not improve significantly. As expected the
existing lake systems function well with regards to settling out of TSS. However, the
existing system does not provide an accessible, cost effective means of permanently
removing sediment that can be achieved with a sediment pool.
¦ Overall pollutant removal efficiencies for the middle ranged particles (P30 and P50) are
higher in alternatives that include a wetland. There is no significant change in removal for
large particles (P80) and dissolved particles (PO) in any alternative.
Water Quality Evaluation 19 February 2005
of Conceptual Plans
¦ Pollutant removal efficiencies for TP are expected to be higher in the Water Quality and
Recommended alternative than reported. P8-UCM does not account for orthophosphorus
uptake in wetlands, which could significantly increase TP removal.
¦ Pollutant removal efficiencies for TN would be expected to be lower than reported TKN
removal values as TKN is a single component of TN. However, these efficiencies should
bounce back for the Water Quality and Recommended alternative. P8-UCM does not
account for ammonium or nitrite/nitrate uptake in wetlands, which could significantly
increase overall TN removal.
¦ The TN removal efficiency for the Water Quality and Recommended alternative should
fulfill a TN reduction of at least 30 percent per Neuse River Nutrient Management Strategy,
although that requirement is for singular, new development.
¦ Furthermore, pollutant removal efficiencies may be negatively impacted without proper
maintenance and harvesting of BMPs that present the opportunity to permanently remove
pollutants from the Lakes system.
¦ The addition of wetlands and sediment pools would provide for more laminar flow regions
near the headwaters of the lake and increase hydraulic residence time. These changes could
increase the potential for fecal coliform die off and lessen downstream impact through
ultraviolet radiation and longer travel time.
This water quality evaluation provides evidence that the Recommended and Water Quality
alternative demonstrate improvement in pollutant removal efficiency over the Dam Safety
alternative, which provides better function of flood control over existing lake conditions by
reconfiguration and construction of new spillways. The relative water quality results of the
alternatives and other benefits of the inclusive design elements should be taken from this TM
and used in the global evaluation of alternatives to be discussed further in an Alternative
Design Summary and Final Report. Their level of value must be weighed against results of
other analyses to determine the best alternative for Northshore and Brentwood Today Lakes.
Water Quality Evaluation 20 February 2005
of Conceptual Plans
SECTION 7.0 - REFERENCES
Haith, D.A. and L.L. Shoemaker, 1987. "Generalized Watershed Loading Functions for Stream
Flow Nutrients", Water Resources Bulletin, American Water Resources Association, Vol. 23 No.
3.
Hamon, W.R., 1961. "Estimating Potential Evapotranspiration", Proceedings of the American
Society of Civil Engineers , Journal of Hydraulics Division, Vol. 87, No. HY3.
US Environmental Protection Agency, 1992. Compendium of Watershed-Scale Models for
TMDL Development, Washington D.C., 841R94002.
US Environmental Protection Agency, 1999. Protocol for Developing Nutrient TMDLs,
Washington D.C., 8411399007.
Wright-McLaughlin Engineers, 1969. Urban Storm Drainage Criteria Manual, Denver, Colorado.
Soil Conservation Service, 1986. Urban Hydrology for Small Watersheds, Technical Release
No. 55, US Department of Agriculture, Washington D.C.
Walker, William W, Jr. Ph.D., 1990. P8 Urban Catchment Model: Program Documentation
Concord, Massachusetts.
Winer, Rebecca, 2000. National Pollutant Removal Performance Results for Stormwater
Treatment Devices, 2nd Edition. Center for Watershed Protection, Elliot City, Maryland.
Water Quality Evaluation 21 February 2005
of Conceptual Plans
Northshore/Brentwood Today Lakes - Adjacent Property Owners
PIN # OWNER Mailing Address Mailing Address 2 Mailing Address 3 Lot Description Street # Street Name Street T e
1725.0519 7143 SIMMONS, VINCENT L & SHELIA B 4016 INGRAM DR RALEIGH NC 27604-3406 LT 52 BLK 25 BRENTWOOD ESTS SECT 10 PT C 4016 INGRAM DR
1725.0519 9140 DICKSON, HOWARD KENNETH JR & KAREN 3900 BEAUMONT CT RALEIGH NC 27604.3452 LT 10 BRENTWOOD TODAY PH III BM 1978.670 3900 BEAUMONT CT
1725.05 29 0026 BRANCH, STEVE & VALERIE C 3904 BEAUMONT CT RALEIGH NC 27604-3452 LOT 11 BRENTWOOD TODAY PH III 3904 BEAUMONT CT
1725.0519 7034 BURRELL, JOSEPHINE H 4012 INGRAM DR RALEIGH NC 27604-3406 LT 51 BLK 25 BRNTWD ESTS SEC 10 PT C 4012 INGRAM DR
1725.0518 7935 BAILLIE, JAMES C 4008 INGRAM DR RALEIGH NC 27604-3406 LT 50 BLK 25 BRENTWOOD EST SEC 10 PT C 4008 INGRAM DR
1725.0518 9982 SHACKLEFORD, ROGER J & JILMA C 3901 PEPPERTREE PL RALEIGH NC 27604.3442 L 18 BRENTWOOD TODAY PH III BM 1978.670 3901 PEPPERTREE PL
1725.0518 7807 BRIDGER, ROBERT CAMERON &SANDRA GAIL MERA 4004 INGRAM DR RALEIGH NC 27604.3406 LT 49 BRENTWOOD EST SEC 10 PT C 1967.180 4004 ING RAM DR
1725.0518 9883 NGUYEN, XUAN VAN & XAM THI DO 3900 PEPPERTREE PL RALEIGH NC 27604.3443 L 19 REV BRENTWOOD TODAY PH 31981.26 3900 PEPPERTREE PL
1725.05 28 0768 MIRCHANDANI, SHARON L 3904 PEPPERTREE PL RALEIGH NC 27604.3443 LOT 20 BRENTWOOD TODAY PHASE III 3904 PEPPERTREE PL
1725.0518 6860 KRIEGSMAN, JEFF 0 4000 INGRAM DR RALEIGH NC 27604.3406 L48 BL 25 BRENTWD EST SC10 PT C BM67.180 4000 INGRAM DR
1725.0518 6723 VOCKEROTH, ALFRED F JR &KATHLEEN J 3920 INGRAM DR RALEIGH NC 27604.3404 LT 47 BLK 25 BRENTWOOD ESTS SEC 10 PT C 3920 INGRAM DR
1725.05 28 0636 BROWN, WILL S III & DEBORAH M 3901 OLD CREEK CT RALEIGH NC 27604.3455 LOT 25 BRENTWOOD TODAY PH III 3901 OLD CREEK CT
1725.0518 5686 LIGGINS, DAVID RICKY & DEBORAH C 3916 INGRAM DR RALEIGH NC 27604.3404 LT 46 BL 25 BRENTWD EST SEC 10 PT C 3916 INGRAM DR
1725.05 28 0537 MUNK, DON E & CHILI CHU LIN 3900 OLD CREEK CT RALEIGH NC 27604.3454 LT 26 BRENTWOOD TODAY PH 3 BM1978-670 3900 OLD CREEK CT
1725.0518 5549 PARKER, JOHN RANDOLPH JR &DORIS B 3912 INGRAM DR RALEIGH NC 27604.3404 L 45 BL 25 BRENTWD EST SEC 10 PT C 3912 INGRAM DR
1725.05 28 0479 BARRESI, PATRICIA EILEEN BOURS 3904 OLD CREEK CT RALEIGH NC 27604.3454 LT 27 BRENTWOOD TODAY PH III BM78-670 3904 OLD CREEK CT
1725.0518 5522 FERRARO, MICHAEL VINCENT 4300 BLAND RD RALEIGH NC 27609-6125 LT 44 BLK 25 BRENTWOOD ESTS SECT 10 PT C 3908 INGRAM DR
1725.0518 5405 PILKINGTON, ALBERT JR & CARLINE 3904 INGRAM DR RALEIGH NC 27604.3404 LT 43 BL 25 BRENTWD EST SEC 10 PT C 3904 INGRAM DR
1725.0518 4387 ROSE, LARRY B & OPE F 3900 INGRAM DR RALEIGH NC 27604-3404 L 42 BL 25 BRENTWD EST SC 10 PT C 67.180 3900 INGRAM DR
1725.0518 9391 KOONS, DARREN J & HEATHER HUGHES 3633 GREYWOOD DR RALEIGH NC 27604.3462 LT 33 BRENTWOOD TODAY PH ,1 BM 1980-678 3633 GREYWOOD DR
1725.0518 4269 BAILEY, LORILYN & STEPHEN E 3828 INGRAM DR RALEIGH NC 27604.3316 LT 41 BLK 25 BRENTWD ESTS SEC 10 PT C 3828 INGRAM DR
1725.0518 9236 MACENTEE, JASON D & ERIN E DOUGH 3629 GREYWOOD DR RALEIGH NC 27604.3462 LOT 34 BRENTWOOD TODAY PHASE 4 3629 GREYWOOD DR
1725.0518 4241 BAILEY, STEPHEN E & LORILYN 3824 INGRAM DR RALEIGH NC 27604.3316 L 40 BL 25 BRENTWD EST SEC .0 PT C 3824 INGRAM DR
1725.0518 8270 JOHNSON, TYRONE B & AGNES C 3625 GREYWOOD DR RALEIGH NC 27604.3462 LT 35 BRENTWOOD TODAY PH 4 BM1980-642 3625 GREYWOOD DR
1725.0518 4114 WILLIAMS, ALVIN & ANNIE S 3820 INGRAM DR RALEIGH NC 27604.3316 LT 39 BLK 25 BRENTWOOD ESTS SECT 10 PT C 3820 INGRAM DR
1725.0518 8123 ELLIOTT, PAUL WAYNE & TERESA L 3621 GREYWOOD DR RALEIGH NC 27604.3462 LT 36 BRENTWOOD TODAY PH 4 (BM1980-678) 3621 GREYWOOD DR
1725.0518 4006 ARCHER, KEIRA T 3816 INGRAM DR RALEIGH NC 27604.3316 L38 & SM ADJ ST BL 25 BRENTWD EST S10 P 3816 INGRAM DR
1725.0518 7097 LAHOUD, MICHAEL A 3617 GREYWOOD DR RALEIGH NC 27604.3462 LT 37 BRENTWOOD TODAY PH 4 BM 1980-678 3617 GREYWOOD DR
1725.0518 7002 FRANZEL, RONALD A & ANN Z 3613 GREYWOOD DR RALEIGH NC 27604.3462 LT 38 BRENTWOOD TODAY PHASE 4 (BM80.678 3613 GREYWOOD DR
1725.0517 4908 ADESUYI, ISRAEL 0 & JACQUELINE MUS DEPARTMENT OF HUD, HOFPA ATTN: SEC-HELD SF NOTES, RM 6240 PO BOX 44813 WASHINGTON DC 20026.4813 L37 BL 25 BRENTWD ESTS SC 10 P C SM ST 3812 INGRAM DR
1725.0517 6936 FREEZE, DAVID A 3609 GREYWOOD DR RALEIGH NC 27604.3462 LT 39 BRENTWOOD TODAY PH 4 BM 1979-224 3609 GREYWOOD DR
1725.0517 4819 FLOWERS, AYDREN D & JEANNETTE P 3808 INGRAM DR RALEIGH NC 27604-3316 LT 36 BILK 25 BRENTWOOD ESTS SEC 10 PT C 3808 INGRAM DR
1725.0517 6837 RIVERA, MANUAL C & DORALICIA D M 3605 GREYWOOD DR RALEIGH NC 27604.3462 LT 40 BRENTWOOD TODAY PH 4 BM 1979-224 3605 GREYWOOD DR
1725.0517 4800 HOULE, RICKY D 3804 INGRAM DR RALEIGH NC 27604.3316 LT 35 BLK 25 BRENTWD ESTS SEC 10 PT C 3804 INGRAM DR
1725.0517 6727 THORPE, BRIAN R 3601 GREYWOOD DR RALEIGH NC 27604.3462 LT 41 BRENTWOOD TODAY PH 4 (BM 1979.224) 3601 GREYWOOD DR
1725.0517 2782 HIGGINS, REGINALD R 3800 INGRAM DR RALEIGH NC 27604.3316 LT 34 BLK 25 BRENTWD ESTS SEC 10 PT C 3800 INGRAM DR
1725.0517 6609 BRITTON, RHONDA K 3533 GREYWOOD DR RALEIGH NC 27604.3347 LT 42 BRENTWOOD TODAY PH 4 BM1979-224 3533 GREYWOOD DR
1725.0517 4606 SMITSHON, ELLA W 3804 CAMARO CT RALEIGH NC 27604.3306 LT 33 BLK 25 BRENTWD EST SEC 10 PT C 3804 CAMARO CT
1725.05 17 5680 PITTMAN, OLIVER L & ANITA M 3529 GREYWOOD DR RALEIGH NC 27604.3347 LT 43 BRENTWOOD TODAY PH 4 BM 1979-224 3529 GREYWOOD DR
1725.0517 3586 VIKLUND, VICTOR L & KATHLEEN G 3808 CAMARO CT RALEIGH NC 27604.3306 LT 32 BLK 25 BRENTWOOD ESTS SECT 10 PT C 3808 CAMARO CT
1725.0917 3423 DANIEL, WILLIAM L JR & CLAUDIA C 3809 CAMARO CT RALEIGH NC 27604.3305 LT 31 BLK 25 BRENTWD ESTS SEC 10 PT C 3809 CAMARO CT
1725.05 17 5544 TURNER, JAMES HENRY 3527 GREYWOOD DR RALEIGH NC 27604.3347 LT 90 ADDT TO BRENTWOOD TODAY BM1980.921 3527 GREYWOOD DR
1725.0917 5435 DUNN, DWIGHT & ANNA M 3525 GREYWOOD DR RALEIGH NC 27604.3347 LT 91 ADDT TO BRENTWOOD TODAY BM 1980-921 3525 GREYWOOD DR
1725.09 17 1395 WOOMER, CLARK FULTON 3717 MARLIN CT RALEIGH NC 27604.3319 LT 19 BLK 25 BRENTWD EST SEC 10 PT B 3717 MARLIN CT
1725.09 17 4399 JOHNSON, TRACEY A &DONNA R JOHNSON 3523 GREYWOOD OR RALEIGH NC 27604.3347 LT 92 ADDT TO BRENTWOOD TODAY BM1980.921 3523 GREYWOOD DR
1725.0917 4341 PRESSLEY, CHRISTINA J & MATTHEW S 3521 GREYWOOD DR RALEIGH NC 27604.3347 LT 93 ADDT TO BRENTWOOD TODAY BM1980.921 3521 GREYWOOD DR
1725.0917 3271 BARBOUR, DANIEL M & LINDA T 3517 GREYWOOD DR RALEIGH NC 27604.3347 LT 94 ADDT TO BRENTWOOD TODAY BM90-1210 3517 GREYWOOD DR
1725.0917 2214 RYAN, DANIEL J 3720 MARLIN CT RALEIGH NC 27604.3320 LT 18 ELK 25 BRENTWD ESTS SEC 10 PT B 3720 MARLIN CT
1725.09 17 1164 MARK, CLYDE M III & ELLEN R 3716 MARLIN CT RALEIGH NC 27604.3320 L17 BL25 BRENTWD ESTS SC10 PT B BM66.241 3716 MARLIN CT
1725.09 17 3121 BAKER, JEANNETTE 3513 GREYWOOD DR RALEIGH NC 27604.3347 LT 95 ADDT TO BRENTWOOD TODAY BM1980.921 3213 GREYWOOD DR
1725.0916 2955 ADAMS BILT COMPANY THE PO BOX 18108 RALEIGH NC 27619.8108 LT 96 ADDT TO BRENTWOOD TODAY BM 1980-921 3509 GREYWOOD DR
1725.0916 0997 BINGHAM, WILLIAM D & PEGGY H 3713 LANCELOT CT RALEIGH NC 276043317 LT 8 BLK 25 BRENTWOOD EST SEC 10 PT B 3713 LANCELOT CT
1725.0916 1813 HUNTER, LEWIS JR & JACQUELINE B 3716 LANCELOT CT RALEIGH NC 27604.3318 LT 7 BLK 25 BRENTWD ESTS SEC 10 PT B 3716 LANCELOT CT
1725.0916 0744 MOORE, SCOTT E 3712 LANCELOT CT RALEIGH NC 27604.3318 LT 6 BLK 25 BRENTWOOD ESTS SC 10 PT B 3712 LANCELOT CT
1725.0916 2607 BILGER, GEORGE JR 3409 GREYWOOD DR RALEIGH NC 27604.3349 LT 101 ADD TO BRENTWOOD TODAY BM90.1210 3409 GREYWOOD DR
1725.0916 0508 ROBERTS, DON LEE & PAULA M 3312 HUNTLEIGH DR RALEIGH NC 27604.3312 LT 1-A BLK 25 BRENTWOOD EST SEC 9 PT C 3312 HUNTLEIGH DR
1725.0916 2500 GALLANT, DANIEL R & VIVIENNE M 3405 GREYWOOD DR RALEIGH NC 27604.3349 LT 102 ADD TO BRENTWOOD TODAY BM1980.921 3405 GREYWOOD DR
1725.09 16 1415 EDUCARE COMMUNITY LIVING CORP 10140 LINN STATION RD LOUISVILLE KY 40223-3813 L 1 BL 25A BRENTWD EST SC 11 BM70.288 3300 HUNTLEIGH DR
1726.18 20 6533 NORTHSHORE HOMEOWNERS ASSOCC/0 JAMES F & MARTHA B WILLIAMS 4313 WATERBURY RD RALEIGH NC 27604.3546 NORTHSHORE LAKE 0 COMSTOCK RD
1726.17 201018 SOUTHERLAND, JIMMIE H &RALEIGH DOUGLAS SOUTHERLAND JR 4308 RYEGATE DR RALEIGH NC 27604.3501 LT 10 BLK A NORTHSHORE SECT 1 4308 RYEGATE DR
1726.17 20 0015 LISOWE, DAVID G 4304 RYEGATE DR RALEIGH NC 27604.3501 LT 9 BLK A NORTHSHORE SEC 1 BM1968.184 4304 RYE ATE DR
1726.1710 9013 BROWN, LINDA W 4120 PITTSFORD RD RALEIGH NC 27604.3459 LT 8 ELK A NORTHSHORE SEC 1 BM1968.184 4120 PITTSFORD RD
1725.06 29 7933 LAWTON, CAROLYN DIANE 3113 DEANA LN RALEIGH NC 27604.3478 LT 40 BLK A NORTHSHORE SEC 1 BM 1968-184 3111 DEANA LA
1725.06 29 8924 GRADUS, PAUL A & BECKWITH S 816 MOUNT VERNON CHURCH RD RALEIGH NC 27614.9283 LT 39 BLK A NORTHSHORE SECT 1 3117 DEANA LA
1725.06 29 6817 CHATHAM, BOBBY CLARKC/O POLLY CHATHAM 8121 LAKISTA POINT LN GARNER NC 27529.9096 LT 41 BL A NORTH SHORE SEC 1 3101 NEW HOPE CHURCH RD
1725.0519 9932 SMITH, ANDRE C & SANDRA WALLACE 4116 PITTSFORD RD RALEIGH NC 27604.3459 LT 7 BILK A NORTHSHORE SEC 1 4116 PITTSFORD RD
1725.0519 9864 WEAVER, HUEY P & DOROTHY A 4112 PITTSFORD RD RALEIGH NC 27604.3459 LT 6 BLK A NORTHSHORE SEC 1' 4112 PITTSFORD RD
Northshore/Brentwood Today Lakes - Adjacent Property Owners
PIN # OWNER Mailing Address Mailing Address 2 Mailing Address 3 Lot Description Street # Street Name Street T e
1725.0519 9786 KODACK, JONATHAN A & JULIE G 4108 PITTSFORD RD RALEIGH NC 27604.3459 LT 5 BL A NORTHSHORE SC 1 BM 1968-184 4108 PITTSFORD RD
1725.05 291730 CHATHAM, B CLARK & POLLY 1 8121 LAKISTA POINT LN GARNER NC 27529.9096 LT 2 BLK A NORTHSHORE SEC 1 3005 NEW HOPE CHURCH RD
1725.05 29 2761 CHATHAM, B CLARK & POLLY 1 8121 LAKISTA POINT LN GARNER NC 27529-9096 LT 1 BLK A NORTHSHORE SEC 1 3019 NEW HOPE CHURCH RD
1725.0519 8700 TOMLINSON, JANET M 4109 PITTSFORD RD RALEIGH NC 27604.3458 LT 7 BLK B NORTHSHORE SECT 1 4109 PITTSFORD RD
1725.0519 6679 BRADY, WILLIE G & JANET S 329 MOSS RD ZEBULON NC 27597-8805 LT 45 SHAMROCK MEADOW SECT 1 2920 DUNSINANE CT
1725.05 29 0618 WOODALL, WILLIAM A & MARY B 4104 PITTSFORD RD RALEIGH NC 27604.3459 LT 4 BLK A NORTHSHORE SECT 1 4104 PITTSFORD RD
1725.0519 8631 FERGUSON, ARTHUR E JR & SUSAN H 4105 PITTSFORD RD RALEIGH NC 27604.3458 LT 6 BL B NORTHSHORE SC 1 BM1968.184 4105 PITTSFORD RD
1725.0519 6670 BERGMAN, WILLIAM C & ELLEN M 2916 DUNSINANE CT RALEIGH NC 27604.3417 LT 44 SHAMROCK MEADOW SEC 1 2916 DUNSINANE CT
1725.05 29 0549 KALU, NENA 3001 NEW HOPE CHURCH RD RALEIGH NC 27604-3427 LT 3 BLK A NORTHSHORE SEC 1 4100 PITTSFORD RD
1725.0519 8571 PIOTROWSKI, STEPHEN & NANCY S 4101 PITTSFORD RD RALEIGH NC 27604.3458 LT 5 BLK B NORTHSHORE SEC 1 4101 PITTSFORD RD
1725.0519 7478 LATKOWSKI, PATRICIA B 2919 NEW HOPE CHURCH RD # R RALEIGH NO 27604.3425 LT 4 BLK B N SHORE SEC 1 2919 NEW HOPE CHURCH RD
1725.05 291303 BEATTY, ROSEMARY 3909 BEAUMONT CT RALEIGH NC 27604-3453 LT 7 BRENTWOOD TODAY PH 1 3909 BEAUMONT CT
1725.05 29 0300 KUO, LIU KUIE HELEN 3905 BEAUMONT CT RALEIGH NC 27604.3453 LOT 8 BRENTWOOD TODAY PHASE ONE 3905 BEAUMONT CT
1725.0518 7587 ADAMS BILT COMPANY THE PO BOX 18108 RALEIGH NO 27619.8108 ARNOLD LD 0 SARATOGA DR
1725.0519 9251 PEARSON, SCOTT C TRUSTEE 222 MONTIBELLO DR CARY NC 27513.2466 LOT 9 BRENTWOOD TODAY PHASE ONE 3901 BEAUMONT CT
1725.0519 7212 FRYE, HARLAN E 2908 NEW HOPE CHURCH RD RALEIGH NO 27604.3426 LT 53 BL 25 BRENTWD EST SIC PT C (ADD) 2908 NEW HOPE CHURCH RD
1726.18 32 4278 CRIT NC LLCCIO MARVIN F POER & CO ATTN: RAV 4 EXECUTIVE PARK W STE 100 ATLANTA GA 30329.2212 PROP NORTH BOULEVARD PLAZA BM 1984.212 4702 BAYRIDGE CRSG
1726.18 321016 MASSENGALE, SUSAN L 4616 WATERBURY RD RALEIGH NO 27604-3553 L224 PT L223 SHAMROCK MDWS SC 5 84.930 4616 WATERBURY RD
1726.18 31 2936 DIDKIVSKA, GANNA &VOLODYMYR DIDKIVSKYY 4600 WATERBURY RD RALEIGH NC 27604.3553 L7 BL G NTHSHORE SC5 PT 223 SHAMROCK MDW 4600 WATERBURY RD
1726.18 31 0838 LANGLEY, BOBBIE LEWIS HARWARD 4613 WATERBURY RD RALEIGH NC 27604-3552 LT 222 SHAMROCK MEADOW SEC 5 BM1973.391 0 WATERBURY RD
1726.18 21 9850 SHARPE, JUDITH P 4608 PAISLEY PL RALEIGH NC 27604.3532 LT 220 SHAMROCK MEADOW SEC 5 BM 1971-200 4608 PAISLEY PL
1726.18 31 0766 LE, LANH THI MELVIN 307 WINDEL DR RALEIGH NC 27609-4443 LT 10 BLK F N SHORES SEC 5 4517 WATERBURY RD
1726.18 21 8792 FORE, CLAYTON LEWIS 4604 PAISLEY PL RALEIGH NC 27604.3532 LT 219 SHAMROCK MEADOW SEC 5 4604 PAISLEY PL
1726.18 310615 REED, WILLIAM S & ELIZABETH B 4513 WATERBURY RD RALEIGH NC 27604-3550 LT 9 BLK F NORTHSHORE SEC 5 4513 WATERBURY RD
1726.18 21 7663 MESSENGER, JUN GILLS 3109 SELKIRK DR RALEIGH NC 27604.3541 LT 206 SHAMROCK MEADOW SEC 5 3109 SELKIRK PL
1726.18 31 0516 BARWICK, ALLEN J & CAROL B 4509 WATERBURY RD RALEIGH NC 27604.3550 LT 8 BLK F NORTHSHORE SEC 5 4509 WATERBURY RD
1726.18 21 8443 ROSSI, LAWRENCE 0 SR & MOZELL H 3113 COMSTOCK RD RALEIGH NC 27604.3506 LT 4 BLK F NORTHSHORE SEC 5 3113 COMSTOCK RD
1726.18 21 7543 NIPPER, JOHN BLOISE JR & LINDA JEAN 3112 SELKIRK DR RALEIGH NC 27604.3542 LT 205 SHAMROCK MDW SEC 5 3112 SELKIRK PL
1726.18 21 7327 BIRGER, BORIS L 3109 COMSTOCK RD RALEIGH NC 276043506 LT 3 BLK F NORTHSHORE SEC 3 3109 COMSTOCK RD
1726.18 21 9211 LUBBERS, JEFFREY A & CAROL A 3116 COMSTOCK RD RALEIGH NC 27604.3507 LT 25 BLK A NORTHSHORE SEC 5 3116 COMSTOCK RD
1726.18 21 8135 PEREZ, POLICARPIO CARRASCO &BLANCA ESTELA REYES 3112 COMSTOCK RD RALEIGH NC 27604.3507 LT 24 BLK A NORTHSHORE SEC 5 BM73.461 3112 COMSTOCK RD
1726.18 21 7128 NORTHSHORE NEIGHBORHOODASSOCIATION INC 4108 PITTSFORD RD RALEIGH NC 27604.3459 3108 COMSTOCK RD
1726.18 31 0220 TRUONG, DIEN NGOC &LOAN THI TRAN 4417 WATERBURY RD RALEIGH NC 27604.3548 LT 26 BLK A NORTHSHORE SEC 5 4417 WATERBURY RD
1726.18 21 9171 REHM, HUBERT H & CHRISTINE M 4413 WATERBURY RD RALEIGH NC 27604-3548 LT 27 BLK A NORTHSHORE SECT 5 4413 WATERBURY RD
1726.18 21 6106 HOLDEN, CHARLES RUDOLPH 4508 RYEGATE DR RALEIGH NC 27604.3538 LOT #23 BLK A NORTHSHORE SECT 3 4508 RYEGATE DR
1726.18 21 5094 KNIGHT, WILLIAM C & ADELINA G 4504 RYEGATE DR RALEIGH NO 27604.3538 LT 22 BLK A NORTHSHORE SEC 3 4504 RYEGATE DR
1726.18 21 9012 THOMPSON, GEORGE E & SHELIA M 4409 WATERBURY RD RALEIGH NO 27604.3548 LT 28 BL A NORTHSHORE SEC 5 BM 1972.2 4409 WATERBURY RD
1726.18 20 6905 TOMLINSON, PAULA V &JOHN D TOMILSON 4500 RYEGATE DR RALEIGH NC 27604.3538 LT 21 BLK A NORTHSHORE SECT 3 4500 RYEGATE DR
1726.18 20 9913 SARGINGER, FRANCIS E JR & PHYLLIS G 4405 WATERBURY RD RALEIGH NC 27604.3548 LT 29 BLK A NORTHSHORE SECT 5 4405 WATERBURY RD
1726.18 20 9813 SCOTT, EDWIN W & SUSAN K 6900 VALLEY RIDGE CT RALEIGH NC 27615.7130 LT 30 BLK A NORTHSHORE SEC 5 4401 WATERBURY RD
1726.18 20 5885 SASNETT, K HAINES & NANCY C 4424 RYEGATE DR RALEIGH NC 27604-3536 LT 20 BLK A NORTHSHORE SECT 1 4424 RYEGATE DR
1726.18 20 5757 TOMLINSON, JOSH W & IDA R 4420 RYEGATE DR RALEIGH NC 27604.3536 LT 19 BLK A NORTHSHORE SEC 1 4420 RYEGATE DR
1726.18 20 9714 WILLIAMS, JAMES FULLER & MARTHA B 4313 WATERBURY RD RALEIGH NC 27604.3546 LT 31 BLK A NORTHSHORE SECT 5 4313 WATERBURY RD
1726.18 20 5647 SHUMATE, MARLENE 4416 RYEGATE DR RALEIGH NC 27604-3536 LT 18 BLK A NORTHSHORE SEC 1 4416 RYEGATE DR
1726.18 20 9615 FINCH, GEORGE C & SYLVIA JEAN 4309 WATERBURY RD RALEIGH NC 27604-3546 LT 32 BLK A NORTHSHORE SEC 5 4309 WATERBURY RD
1726.17 20 4651 RICHARDSON, CHANDLER 0 & CYNTHIA P 4412 RYEGATE DR RALEIGH NC 27604.3536 LT 17 BLK A NORTH SHORE SECT 1 4412 RYEGATE DR
1726.18 20 8574 SIMS, WELFORD M & CAROL C 4305 WATERBURY RD RALEIGH NO 27604.3546 LT 33 BLK A NORTH SHORE SECT 4 4305 WATERBURY RD
1726.17 20 4523 HUTAFF, THOMAS G & KRISTIE R 4408 RYEGATE DR RALEIGH NO 27604.3536 LT 16 BLK A NORHTSHORE SEC 1 4408 RYEGATE DR
1726.18 20 8435 MCCONNELL, GARY D & LISA S 4301 WATERBURY RD RALEIGH NC 27604.3546 LT 34 BLK A NORTHSHORE SC 4 4301 WATERBURY RD
1726.17 20 3485 FINNERTY, WILLIAM EDWARD & NORMA J 4404 RYEGATE DR RALEIGH NO 27604.3536 LT 15 BLK A NORTHSHORE SEC 1 BM 1968-184 4404 RYEGATE DR
1726.17 20 3347
- WHAREY, SHERYL SWITZER & PAUL 4400 RYEGATE OR RALEIGH NC 27604.3536 LT 14 BLK A NORTHSHORE SEC 1 4400 RYEGATE DR
1726.18 20 8317 HAYES, YVONNE S &ELIZABETH BUNCH 4217 WATERBURY RD RALEIGH NC 27604.3448 LT 35 BLK A NO SHORE SECT 4 4217 WATERBURY RD
1726.17 20 3228 WHITE, LIDIA A 4320 RYEGATE DR RALEIGH NO 27604.3501 LT 13 BLK A NORTHSHORE SEC 1 BM1968.184 4320 RYEGATE DR
1726.18 20 8217 MILLER, PATRICIA B 4213 WATERBURY RD RALEIGH NC 27604.3448 LT 36 BLK A NORTHSHORE SEC 4 4213 WATERBURY RD
1726.17 20 2270 BIGGERS, JACK L 4316 RYEGATE OR RALEIGH NO 27604.3501 LT 12 BLK A NORTH SHORE SEC 1 4316 RYEGATE DR
1726.18 20 8108 JONES, DOROTHY F 4209 WATERBURY RD RALEIGH NO 27604.3448 LT 37 BLK A NORTHSHORE SEC 4 4209 WATERBURY RD
1726.17 201193 PURSER, HAUGHTON CHUNN & FUSAKO M 4312 RYEGATE DR RALEIGH NO 27604-3501 LT 11 BLK A NORTHSHORE SECT 1 4312 RYEGATE DR
1726.18 20 7077 SPRISSLER, DANIEL L & CRYSTAL D 109 SOUTH BND KNIGHTDALE NC 27545-9795 LT 38 BLK A NORTHSHORE SEC 4 BM670.323 4205 WATERBURY RD
1 1
J1
US Army Corps PUBLIC NOTICE
Of Engineers
Wilmington District
Issue Date: July 15, 2005
Comment Deadline: August 15, 2005
Corps Action ID #: 200421569
All interested parties are hereby advised that the Wilmington District, Corps of Engineers
(Corps) has received an application for work within jurisdictional waters of the United
States. Specific plans and location information are described below and shown on the
attached plans. This Public Notice and all attached plans are also available on the
Wilmington District Web Site at www.saw.usace.army.miI/wetlands
r7on /--N
Applicant: City of Raleigh L?l U[99 t/ IS D
Attn: Mr. Carl R. Dawson Jr. R
Public Works Department JUL 2 0 2005
Post Office Box 590
City of Raleigh, NC 27602-0590 %-EMMSA14DSTT ORMATERIBUX-1-1
Authority
The Corps will evaluate this application and decide whether to issue, conditionally issue,
or deny the proposed work pursuant to the applicable procedures of Section 404 of the
Clean Water Act.
Location
The project, Northshore and Brentwood Today Dam and Lake Rehabilitation, is located
on the north and south of New Hope Church Road, approximately 0.5 miles west of
Capital Boulevard (U.S. Highway 1), in Raleigh, Wake County, North Carolina.
Coordinates (in decimal degrees) for the site are 35.8370°North, 78.5875 ° West. The
project site contains an unnamed tributary to Marsh Creek, and adjacent wetlands, in the
Neuse River Basin (8-Digit Cataloging Unit 03020201).
Existing Site Conditions
Northshore and Brentwood Today are the second and third lakes in a series of four lakes
that occurs along a 2-mile stretch of an unnamed tributary to Marsh Creek. Northshore
Lake is approximately 7.68 acres in size and Brentwood Today Lake is approximately 4.4
acres in size. Both lakes were originally constructed more than 50 years ago as amenities
to the surrounding residential developments. Below the lowest lake in the series, the
tributary flows into Marsh Creek, which in turnflows into Crabtree Creek about two
miles downstream. The land use in the area immediately adjacent to the lakes is
primarily medium to high-density residential subdivisions. A substantial portion of the
watershed that drains into the lakes also consists of commercial and industrial areas
located along the Capital Boulevard corridor.
Both Northshore Lake and Brentwood Today Lake have been experiencing significant
sediment deposition over the last several decades, due in large part to development
activities that have occurred in the drainage basin. The deepest portions of both lakes
have an estimated 3-5 feet of sediment buildup, and the upper ends of the lakes have
become very shallow. The accumulation of sediment has also led to the development of
wetland areas in the headwater regions of both lakes. Additionally, both lakes have
received increasing amounts of stormwater runoff as the extent of impervious surface has
increased in their watershed. Spillways for both lakes have also significantly eroded and
are in poor condition. The City has stated that both dams have been a safety concern for
more than 20 years.
Applicant's Stated Purpose
As stated by the applicant, the project has three primary objectives: 1) to address NC
Dam Safety concerns for long-term stability and downstream protection; 2) to identify
opportunities for water quality enhancement of the watershed supplemental to ongoing
City efforts; and 3) to preserve property value for the neighborhoods surrounding the
lakes.
Project Description
The project involves the reconstruction of the dam and spillway structures for Northshore
and Brentwood Today Lakes, as well as excavation and reshaping activities within both
lakebeds. For Northshore Lake, the dam is proposed to be improved to meet dam safety
requirements. The primary spillway structure would be enlarged and protrude into the
lakebed. A 150-foot weir at elevation 265.9 would be constructed along the front edge of
the spillway in order to pass expected high flows. The spillway would be notched for 25
feet down to an elevation of 263 feet, and 2-inch water-quality drawdown holes would be
placed at elevation 262. The drawdown holes would pass the normal daily flows and
establish the new normal pool of the lake at 262 feet, a drop of 2.5 feet from the existing
normal pool of the lake. The work would result in a 1.5-foot increase in the flood storage
capacity of the structure.
Approximately 1.5 acres of the lakebed would be dredged to remove accumulated
sediment. Most of the dredging would occur in upper portions of the lakebed and around
the perimeter of the lake. The dredging would allow the overall surface area of the lake
to remain approximately equal to current conditions. Plans also call for the construction
of a 0.8-acre sediment pool at the upper end of the lake just south of Comstock Road.
The pool would be constructed in a spot that currently contains a house that would have
to be removed. The sediment pool would be constructed to allow periodic maintenance
dredging to remove sediment build-up. Additionally, a 0.7-acre headwater wetland
2
would be constructed just downstream of the sediment pool to help filter nutrients and
contaminants. Small plunge pool structures are also proposed at the outlets of existing
outfalls and channels to provide treatment for sediment and contaminant runoff.
Impacts to Waters of the U.S. associated with the rehabilitation to Northshore Lake
include the temporary disturbance of 1.5 acres of lakebed for dredging, and the
permanent loss of 0.08 acre of open water for construction of the spillway device. The
reduction of the normal pool of the lake and construction of the sediment pool would also
lead to the loss of 0.46 acre of riparian forested wetland, 0.03 acre of fringe wetland, 0.51
acre of open water, and 260 linear feet of perennial stream channel that is currently
inundated by the lake.
For Brentwood Today Lake the dam would be upgraded with a new spillway. The
spillway would have a 100-foot weir at elevation 245.2, with a 20-foot notch cut down to
242 feet. No change in water level is proposed to the lake. Approximately 3 acres of
lakebed would be dredged to remove accumulated sediment, and a 0.4-acre sediment pool
would be created where a primary tributary enters the lake along the eastern side. A
smaller sediment pool is also proposed just downstream of New Hope Church Road, and
a plunge pool would be constructed on the western side of the lake. The majority of
existing wetlands within the lake would be preserved.
Impacts to Waters of the U.S. associated with the rehabilitation to Brentwood Today
Lake include the temporary disturbance of 3 acres of lakebed for dredging, and the
permanent loss of 0.04 acre of open water for construction of the spillway. Spillway
construction will also impact 50 linear feet of unstable perennial stream channel that has
developed in the location of the eroded spillway. The construction of the sediment pool
at the tributary draining into the eastern side of the lake would also lead to the loss of
0.07 acre of forested wetlands and 80 linear feet of perennial stream channel.
The impact to jurisdictional areas resulting from the rehabilitation of both lakes totals 4.5
acres of temporary disturbance due to dredging, the loss of 0.63 acre of open waters, 0.53
acre of forested wetlands, 0.03 acre of fringe wetlands, and 390 linear feet of stream
channel. Plans included with this notice that show the project details as well as the
details for impacted streams and wetlands.
The applicant does not propose specific mitigation for impacts resulting from the project
because one of the primary purposes of the project is to improve water quality.
Additionally, as part of the project, a 0.7-acre forested wetland is proposed to be created
at the upper end of Northshore Lake, and it is expected that more than 0.5 acres of
wetlands will develop in portions of the exposed lakebed once the water level is lowered.
Other Required Authorizations
This notice and all applicable application materials are being forwarded to the appropriate
State agencies for review. The Corps will generally not make a final permit decision
until the North Carolina Division of Water Quality (NCDWQ) issues, denies, or waives
State certification required by Section 401 of the Clean Water Act (PL 92-500). The
receipt of the application and this public notice in the NCDWQ Central Office in Raleigh
serves as application to the NCDWQ for certification. A waiver will be deemed to occur
if the NCDWQ fails to act on this request for certification within sixty days of the date of
the receipt of this notice in the NCDWQ Central Office. Additional information
regarding the Clean Water Act certification may be reviewed at the NCDWQ Central
Office, 401 Oversight and Express Permits Unit, 2321 Crabtree Boulevard, Raleigh,
North Carolina 27604-2260. All persons desiring to make comments regarding the
application for certification under Section 401 of the Clean Water Act should do so in
writing delivered to the North Carolina Division of Water Quality (NCDWQ), 1650 Mail
Service Center, Raleigh, North Carolina, 27699-1650 Attention: Ms Cyndi Karoly by
August 8, 2005.
Essential Fish Habitat
This notice initiates the Essential Fish Habitat (EFH) consultation requirements of the
Magnuson-Stevens Fishery Conservation and Management Act. The Corps' initial
determination is that the proposed project will not adversely impact EFH or associated
fisheries managed by the South Atlantic or Mid Atlantic Fishery Management Councils
or the National Marine Fisheries Service.
Cultural Resources
The Corps has consulted the latest published version of the National Register of Historic
Places and is not aware that any registered properties, or properties listed as being
eligible for inclusion therein are located along the project corridor or will be affected by
the proposed work. Presently, unknown archeological, scientific, prehistoric, or
historical data may be located within the project area and/or could be affected by the
proposed work.
Endangered Species
The Corps has reviewed the project area, examined all information provided by the
applicant and consulted the latest North Carolina Natural Heritage Database. Based on
available information, the Corps has determined pursuant to the Endangered Species Act
of 1973, that the proposed project will have no effect on federally listed endangered or
threatened species or their formally designated critical habitat.
Evaluation
The decision whether to issue a permit will be based on an evaluation of the probable
impacts, including cumulative impacts, of the proposed activity on the public interest.
That decision will reflect the national concern for both protection and utilization of
important resources. The benefit which reasonably may be expected to accrue from the
proposal must be balanced against its reasonably foreseeable detriments. All factors
which may be relevant to the proposal will be considered including the cumulative effects
4
thereof; among those are conservation, economics, aesthetics, general environmental
concerns, wetlands, historic properties, fish and wildlife values, flood hazards, flood plain
values (in accordance with Executive Order 11988), land use, navigation, shoreline
erosion and accretion, recreation, water supply and conservation, water quality, energy
needs, safety, food and fiber production, mineral needs, considerations of property
ownership, and, in general, the needs and welfare of the people. For activities involving
the discharge of dredged or fill materials in waters of the United States, the evaluation of
the impact of the activity on the public interest will include application of the
Environmental Protection Agency's 404(b)(1) guidelines.
Commenting Information
The Corps is soliciting comments from the public; Federal, State and local agencies and
officials, including any consolidate State Viewpoint or written position of the Governor;
Indian Tribes and other interested parties in order to consider and evaluate the impacts of
this proposed activity. Any comments received will be considered by the Corps to
determine whether to issue, modify, condition or deny a permit for this proposal. To
make this decision, comments are used to assess impacts on endangered species, historic
properties, water quality, general environmental effects and the other public interest
factors listed above. Comments are used in the preparation of an Environmental
Assessment (EA) and/or an Environmental Impact Statement (EIS) pursuant to the
National Environmental Policy Act (NEPA). Comments are also used to determine the
need for a public hearing and to determine the overall public interest of the proposed
activity.
Any person may request, in writing, within the comment period specified in this notice,
that a public hearing be held to consider the application. Requests for public hearings
shall state, with particularity, the reasons for holding a public hearing. Requests for a
public hearing shall be granted, unless the District Engineer determines that the issues
raised are insubstantial or there is otherwise no valid interest to be served by a hearing.
Written comments pertinent to the proposed work, as outlined above, will be received
by the Corps of Engineers, Wilmington District, until 5pm, August 15, 2005. Comments
should be submitted to Todd Tugwell, Raleigh Regulatory Field Office, 6508 Falls of the
Neuse Road, Suite 120, Raleigh, NC 27615.

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RECEIVED
JUN '3 0 2000
RALEIGH REGULATORY FIELD OFFICE
3pmueys WV Lo:LS:oL Soon [1z `al9ad 'JMO'J13£0-Q0M17SL61H0131vu 30 A1101WONIMM

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June 29, 2005
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JUN 3 0 2005
RALEIGHREGULATORyFIELD OFFICE
R19@R9WRP
JUL 2 0 2005
Mr. Todd Tugwell, Project Manager
U. S. Army Corps of Engineers DENR - WATER QUALITY
Raleigh Regulatory Office 1ti'EWDS AND STORIMATER 6UXI-I
6508 Falls of Neuse Road - Suite 120
Raleigh, NC 27615
RE: Northshore and Brentwood Today Lakes Rehabilitation Project
Raleigh, North Carolina
Dear Mr. Tugwell:
Enclosed is an individual permit application, under Section 404 of the Clean Water Act (CWA),
for the Northshore and Brentwood Today Lakes Rehabilitation Project. The City of Raleigh
contracted HDR Engineering, Inc. of the Carolinas (HDR) to perform a study of these lakes,
prepare alternative recommendations, and coordinate public input on the rehabilitation of these
facilities. This permit application includes this cover letter, ENG Form 4345, associated
attachments, permit impact sheets, and a list of property owners as specified in the application
requirements. The application is being submitted for CWA Section 404 permit approval, CWA
Section 401 certification, and Neuse Buffer certification under the Neuse River Riparian Buffer
Rules.
Although this plan and design are conceptual in nature, the impacts are primarily related to the
repair and rehabilitation of the spillways and dams, and the reduction of water level in
Northshore Lake. The design of the spillway structures and the reduction of water levels have
reached the point where an impact estimate can be made. Therefore, the City is submitting this
pennit application for your review and feedback in order to gain input and comments that will be
incorporated into the final design and, if needed, pen-nit re-application. Additional design will be
occurring as the project continues, but should not significantly change the impacts discussed
below.
OFFICES • 222 WEST HARGETT STREET • POST OFFICE BOX 590 • RALEIGH. NORTH CAROLINA 27602
RECYCLED PAFER
Mr. Todd Tugwell
June 29, 2005
Page Two
Please contact me at telephone number 890-3931 if I may answer any questions concerning this
application or be of further assistance.
Sincerely,
17Q? Lt.
James K. Leumas, P. E.
Senior Project Engineer
JKL/
Enclosures
cc: Mr. Carl R. Dawson, Jr., P. E.
Mr. H. Daniel Bowden, P. E.
Ms. Veronica L. High, E. I.
Ms. Cyndi Karoly
Mr. Ronald A. Geiger, P. E.
Ms. Cyndi Karoly
June 29, 2005
Page Two
Please contact me at telephone number 890-3931 if I may answer any questions concerning this
application or be of further assistance.
Sincerely,

James K. Leumas, P. E.
Senior Project Engineer
JKL/
Enclosures
cc: Mr. Carl R. Dawson, Jr., P. E.
Mr. H. Daniel Bowden, P. E.
Ms. Veronica L. High, E. I.
Mr. Todd Tugwell
Mr. Ronald A. Geiger, P. E.
APPLICATION FOR DEPARTMENT OF THE ARMY PERMIT
/33 CFR 3251 31, 2004
The Public burden for this collection of information is sestimated to average 10 hours per response, although the majority of applications should require
5 hours or less. This includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and
completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of
information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Service Directorate of Information
Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302; and to the Office of Management and Budget,
Paperwork Reduction Project (0710-0003), Washington, DC 20503. Respondents should be aware that notwithstanding any other provision of law,
no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control
number. Please DO NOT RETURN your form to either of those addresses. Completed applications must be submitted to the District Engineer having
jurisdiction over the location of the proposed activity.
PRIVACY ACT STATEMENT
Authorities: Rivers and Harbors Act, Section 10, 33 USC 403; Clean Water Act, Section 404, 33 USC 1344; Marine Protection , Research and
Sanctuaries Act, 33 USC 1413, Section 103. Principal Purpose: Information provided on this form will be used in evaluating the application.for a
permit. Routine Uses: This information may be shared with the Department of Justice and other federal, state, and local government agencies.
Submission of requested information is voluntary, however, if information is not provided the permit application cannot be evaluated nor can a permit
be issued.
One set of original drawings or good reproducible copies which show the location and character of the proposed activity must be attached to this
application (see sample drawings and instructions) and be submitted to the District Engineer having jurisdiction over the location of the proposed
activity. An application that is not completed in full will be returned.
1. APPLICATION NO. O(' ? I C / C1 I 2 CICDS?ICODj & ? F, I 3. DATE RECEIVED I4. DATE APPLICATION COMPLETED
2 '1
5. APPLICANT'S NAME 8. AUTHORIZED AGENT'S NAME AND TITLE tan agent is not required)
Carl R. Dawson Jr., PE, Public Works Director
City of Raleigh, Public Works Department
6. APPLICANT'S ADDRESS 9. AGENT'S ADDRESS
City of Raleigh, Public Works Department
PO Box 590 Raleigh, NC 27602-0590
a. Residence I a. Residence
b. Business 919-890-3030 1 b. Business
11. STATEMENT OF AUTHORIZATION
I hereby authorize, to act in my behalf as my agent in the processing of this application and to
iurnish, upon request, supplemental information in support of this permit application.
APPLICANT'S SIGNATURE DATE
NAME, LOCATION AND DESCRIPTION OF PROJECT OR ACTIVITY
12. PROJECT NAME OR TITLE (see instructions!
Northshore and Brentwood Today Dam and Lake Rehabilitation
'13. NAME OF WATERBODY, IF KNOWN or.pplicabiel 14. PROJECT STREET ADDRESS ffapplicab/e)
Northshore Lake and Brentwood Today Lake, both on the New Hope
to Marsh Creek
15. LOCATION OF PROJECT
Wake County
COUNTY
North Carolina
STATE
16. OTHER LOCATION DESCRIPTIONS, IF KNOWN, (see instructions)
Northshore Lake Dam coordinates: Latitude 35 deg. 50 min. 13 sec. / Longitude 78 deg. 35 min. 16 sec.;
Brentwood Today Lake Dam coordinates: Latitude 35 deg. 49 min. 56 sec. / Longitude 78 deg. 35 min. 24 sec.
17. DIRECTIONS TO THE SITE
Take 1-440 Beltline to Capital Boulevard, proceed north on Capital approximately 2 miles to New Hope Church Road, turn left on New Hope
Church, after -1/4-mile you will pass Deana Lane on the right, Northshore Lake is then immediately to your north (right) and Brentwood Today
Lake is to your south (left)
G FORM 4345, u 97 EDITION OF FEB 94 IS OBSOLETE. (Proponent: CECW-OR)
18. Nature of Activity (Descriprion of project, indudeall feeturesJ
This activity includes repair and rehabilitation of Northshore and Brentwood Today dams and spillways, dry ?"of b'othT2syntgv?te+F?n9 of
the water level in Northshore Lake for flood control. [See attachment] it •`et ?? ,jam t1
JUN 3 0 2005
U
19. Project Purpose (Describe the reason or purpose of the project, see instructions) ititti u xL UL A'1 UR, 1•' ELD OFFICE
These two lakes are privately-owned earthen dams with a recent history of overtopping during high flood events. Both dams and spillways are
in need of repair. The lakes are surrounded by residential homes and apartments that are subject to flooding. New Hope Church Road, just
downstream of Northshore Lake, could wash out due to an overtopping event. Both lakes have filled in with sediment over the past several
decades, thereby decreasing water quality. [See attachment]
USE BLOCKS 20-22 IF DREDGED AND/OR FILL MATERIAL IS TO BE DISCHARGED
20. Reason(s) for Discharge
Discharges are mainly related to the repair and rehabilitation of the dams and spillways. Some additional discharges will be associated with the
sediment pool construction and establishment of fringe wetlands around the lakes. [See attachment]
21. Type(s) of Material Being Discharged and the Amount of Each Type in Cubic Yards
[See attachment]
22. Surface Area in Acres of Wetlands or Other Waters Filled /seeinsrructions)
[See attachment]
23. Is Any Portion of the Work Already Complete? Yes No X IF YES, DESCRIBE THE COMPLETED WORK
24. Addresses of Adjoining Property Owners, Lessees, Etc., Whose Property Adjoins the Waterbody (If more than can be entered here,
please attach a supplemental list).
See attached list
25. List of Other Certifications or Approvals/Denials Received from other Federal, State or Local Agencies for Work Described in This Application.
AGENCY TYPE APPROVAL' IDENTIFICATION NUMBER DATE APPLIED DATE APPROVED DATE DENIED
Would include but is not restricted to zoning, buildina and flood plain permits
26. Application is hereby made for a permit or permits to authorize the work described in this application. I certify that the information in this
application is complete and accurate. I further certify that I possess the authority to undertake the work described herein or am acting as the
duly authorized e o th applicant.
? 2,916S
SIGNATURE OF APPL ANT DATE SIGNATURE OF AGENT DATE
The application must be signed by the person who desires to undertake the proposed activity (applicant) or it may be signed by a duly
authorized agent if the statement in block 11 has been filled out and signed.
18 U.S.C. Section 1001 provides that: Whoever, in any manner within the jurisdiction of any department or agency of the United States
knowingly and willfully falsifies, conceals, or covers up any trick, scheme, or disguises a material fact or makes any false, fictitious or
fraudulent statements or representations or makes or uses any false writing or document knowing same to contain any false, fictitious or
fraudulent statements or entry, shall be fined not more than $10,000 or imprisoned not more than five years or both.
Northshore and Brentwood Today Dam and Lake Rehabilitation
List of Permit Application Attachments
Permit Narrative (with Photographs)
Figures 1-7 (includes Project Vicinity Map)
Preliminary Spillway Drawings (3 figures)
Email Communication with Becky Fox of the USEPA
Technical Memorandum No. 4 (Water Quality Evaluation of Conceptual Plans)
List of Adjacent Property Owners
Nortlishore and Brentwood Today Dam and Lake Rehabilitation Project
Section 404 Permit and Section 401/Netcse Buffer Certification Narrative
The narrative below is a thorough description of the project. Under each heading, the
corresponding item from ENG Form 4345 is listed in parentheses if applicable. For
continuity and readability reasons, the items are not necessarily in the order they occur in
the permit, and additional items are included for justification of the project.
Project Background and Purpose (Item 19)
There are a series of four lakes along the New Hope tributary to Marsh Creek and
Crabtree Creek: an unnamed lake, Northshore Lake, Brentwood Today Lake, and
Beaman Lake. The dam at Beaman Lake was breached several years ago and
reconstruction was recently completed to restore the dam embankment and install
features to improve water quality, including constructed wetlands.
This Project includes Northshore Lake and Brentwood Today Lake, which are located in
the City of Raleigh (City) near New Hope Church Road and west of U.S. Highway 1
(Capital Blvd.) as shown in Figure 1. The dams at both Lakes were identified as small,
high hazard dams in a report by Titan Atlantic dated July 20, 2004. Furthermore, the
spillways at both Lakes have been a safety concern for over 20 years. The dams have
been overtopped several times in recent years, causing flooding in the surrounding
residential area. There is also concern that New Hope Church Road, located just
downstream of Northshore Dam, has the potential to wash out during an overtopping
event.
In addition to safety concerns, development in the drainage basin over the last several
decades has created a significant amount of runoff and sedimentation entering these
lakes. Both Northshore and Brentwood Today have an estimated 3-5 feet of sediment in
their lower, deeper areas, and are very shallow in the upper ends with less than a foot of
water in some areas. Peninsula wetlands have been created in the headwater regions of
both lakes through accumulation of sediment. Algae and other noxious plants are present
throughout the lakes, but are concentrated in these shallow upper-headwater areas.
In 2004, the City of Raleigh (City) made a commitment to evaluate the potential of
rehabilitating the Northshore Lake and the Brentwood Today Lake dams and spillways to
minimize and/or prevent flooding to the neighboring property owners as well as improve
public safety downstream. The analysis of these two lakes was driven by three primary
objectives:
1) Address NC Dam Safety concerns for long-term stability and downstream
protection
2) Identify opportunities for water quality enhancement of the watershed
supplemental to ongoing City efforts
3) Preserve property value for the neighborhoods surrounding these lakes.
Northshore & Brentwood Today lakes Page 2 of 15
4041401 Permit Application Narrative
The underlying goal for this effort is to provide a project that addresses these objectives
while achieving public support and meeting the goals of the City of Raleigh's Storm
Water Program. The planning process provided the basis for conceptual layouts for
rehabilitating the dam structures while also increasing water storage capacities and water
quality benefits. The conceptual layouts, discussed in the alternatives analysis section,
were produced with City input and presented for public comment. This planning process
provided a recommended plan comprising dam safety and water quality benefits. Both
lakes are located within the Marsh Creek watershed, which exhibits serious nutrient-
loading problems. This concept would help to reduce some of this nutrient loading as
discussed below.
Project Description (Item 18)
Although two separate lakes, the recommended improvements to these facilities are being
proposed in conjunction due to the overall purpose of this project. The analysis of
alternatives and development of a recommended plan were performed using a watershed
approach to the water quality issues, while looking individually at the project components
such as each dam and spillway. This plan development included incorporation of the
available flood control capacity of Northshore Lake, and the water quality improvements
of Beaman Lake to yield an overall approach for the New Hope tributary watershed.
Northshore Lake (Figure 2)
The Northshore Lake recommended plan is focused on long-term aquatic habitat
and nutrient-removal improvements, in addition to the required dam safety
improvements. An approximate 0.8-acre sediment pool is proposed to be located
just south of Comstock Road within the old Northshore Marina lot and an
adjacent parcel that currently contains a residential structure. The house is
located within the 100-year floodplain and is considered a hazard for flooding.
The sediment pool would require periodic maintenance in order to remove the
sediment build-up. Upland areas around the sediment pool would be set aside for
maintenance access and storage. The pool will serve the same function that the
lake has been providing by trapping sediment, but this will limit the area requiring
maintenance and increase accessibility.
Normal pool elevation would be dropped 2.5 feet to a normal pool elevation of
262 feet in order to provide additional flood storage without raising the dam and
impacting adjacent landowners. The proposed spillway structure is a notched
drop-chute spillway that would incorporate a 25-foot-wide weir at an elevation of
263'. In order to pass high flows, a 150-foot weir length would be constructed at
an elevation of 265.9'. To minimize impacts to the dam, the structure will
protrude into the lake. The hardened channel below the weir would slope from an
invert elevation of 261' down to 256', where it would then tie into the existing
channel below the dam. In addition, several 2" water-quality drawdown holes
using orifice plates at an elevation of 262' will be included in the spillway. These
holes will reduce clogging and will pass the daily flow in addition to any
floodwaters stored between 262' and 263'. Flood storage capacity would be
Northshore & Brentwood Today Ides
4041401 Permit Application Narrative
Page 3 of 15
increased by 1.5 vertical feet with an additional 1-foot drawdown for water
quality improvement purposes.
Approximately 1.5 acres of the lake would be dredged to remove much of the
depositional sediment that has accumulated over the 50+-year life of the lake.
Using existing bathymetry as a guide, the dredging would occur in the upper
portions of the lake and around parts of the lake perimeter. The dredging would
also be performed in order to keep the lake surface area approximately equal to
current conditions. Since some of the existing wetlands may be drained due to the
drop in water elevation, planting of created headwater wetland areas may occur to
enhance their development. An approximate 0.7-acre headwater wetland would
be created below the sediment pool to help filter out nutrients and contaminants
prior to reaching the lake. This headwater wetland will be planted with trees and
constructed such that shallow channels braid through the system. Small plunge
pools are proposed where existing point-source pipes and channels discharge
directly into the lake. These would provide some treatment for sediment and
contaminant runoff from the stormwater outfalls.
Brentwood Today Lake (Fillure 3)
The Brentwood plan would provide primarily for spillway replacement and lake
bathymetry restoration. The existing spillway structure has been progressively
failing over a period of years and needs to be addressed relatively soon in order to
prevent a complete failure of the spillway (a failure of this magnitude may result
in an outflow that could adversely impact downstream lives and property in
addition to the aforementioned Beaman Lake reconstruction project). The
proposed structure would have a 100-foot weir length at an elevation of 245.2'
with a 20-foot notch cut down to 242'. The channel invert below the weir would
be 238', sloping down on a 1-percent grade to an energy-dissipating structure at
the confluence with the existing stream channel. No change in water level is
proposed for this lake since it would add only a minor amount of additional flood
storage.
Approximately 3 acres of lakebed would be dredged. A 0.4-acre sediment pool
would be created where an eastern tributary enters the lake. A plunge pool along
the western shoreline and a sediment pool below New Hope Church Road are also
proposed in this plan. Other than the minor wetland impact from the eastern
sediment pool, the wetlands on-site are to be preserved in order to provide water
quality and habitat benefits.
Alternatives Analysis
The attached technical memoranda describe the Concept Plans shown in Figures 2
through 3, along with the analysis used in the evaluation of these alternatives. In general,
three alternatives were evaluated for each lake:
¦ Dam safety and flood attenuation,
Northshore & Brennvood Today Lakes Page 4 of 15
4041401 Permit Application Narrative
¦ Water quality improvements, and
¦ A composite plan integrating dam safety and water quality (Recommended Plan).
The dam safety recommendations were integrated into all three alternative scenarios,
since exclusion of these recommendations was not practical due to public safety
concerns. Therefore, a "no action alternative" was not considered for permitting
purposes for this project.
The analysis, fully documented in the attached technical memoranda, resulted in the
recommendation of the plan described above. This plan included the required elements
for dam safety and flood attenuation, and incorporated both water quality elements and
public interests. The resulting project yields an increase in water quality efficiency of the
facilities, while satisfying to the greatest practical extent the needs and interests of the
adjacent landowners.
Project Impacts, Minimization, and Avoidance (Items 20, 21, 22)
The impacts of the proposed project on each type of jurisdictional area are presented in
Table 1 and discussed by site below. Along with each impact description is a discussion
of the minimization and avoidance performed at each site. Overall, impacts are mostly
limited to the original footprint of the lakes and spillways prior to the sedimentation and
infilling that has occurred over their 50+-year existence. Stream and wetland delineation
was performed in April-May 2004, and field-verified by Ms. Jennifer Burdette on July
13, 2004 (existing conditions are shown in Figures 4a, 4b, 5a, and 5b; proposed
conditions with impacts in Figures 6a, 6b, 7a, and 7b).
Table 1: Imnact Summarv
Site
Number Lake open
Water ac Forested Wetland
Impact ac Fringe
Wetlands ac Stream
Channel U.
1 Northshore 0.51 0.46 - 260
2 Northshore - - 0.03 -
3 Northshore 0.08 - - -
4 Brentwood Today - 0.07 - 80
L 5 Brentwood Today 0.04 - - 50
Totals 0.63 0.53 0.03 390
Site 1 - Northshore Headwaters:
0.46 acres of riparian forested wetlands will be impacted in this area due to the
drop in the normal pool elevation of the lake (Figure 6a). This will eliminate the
hydrologic conditions necessary for the survival and propagation of the wetland
species currently present. In addition, over time the hydric soil characteristics of
this area will be eliminated and the area will likely revert to an upland riparian
system. 0.51 acres of pond will be converted to wetland due to the reduction in
water levels. This area will be planted with riparian wetland vegetation in order
to enhance the water quality benefits of the project and replace the habitat lost in
the draining of the current wetland areas. Approximately 0.18 acres of the 0.46
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Page 5 of I5
acres of wetlands will also be excavated to allow for the construction of a 0.8 acre
sediment pool or forebay within the original footprint of the lake. This forebay
will be used to minimize the amount of maintenance required in the future and
limit this activity to an easily accessible area. The forebay construction will
impact an additional 260 linear feet of perennial stream channel that is currently
inundated by the lake.
Avoidance of this impact was not practical due to the heavy historical and current
sediment load that has led to the conditions described above. An off-line
sediment pool or forebay was considered for this location in order to avoid
impacting the current stream channel and wetlands. This would have divided the
forebay into two sections on either side of the stream and greatly reduced the
volume of water controlled. In addition, normal base flows would have been
passed by the stream without contact with the sediment pools. Since the entire
lake is currently acting as a sediment pool for the upstream drainage, it was
determined that an in-line forebay was the most practical option.
Draining of the current wetland areas was examined to determine if there were
options to avoid this impact. However, since flood control is a primary concern
below the dam, the water level has been decreased in the Recommended Plan to
provide additional flood storage and spillway capacity, which brings the dam's
spillway capacity into compliance with the NC Dam Safety Act. Since the flood
control storage drop of 1.5 feet is necessary and would drain the wetlands at the
site, it was determined that an additional 1 foot of water drop would be beneficial
for water quality purposes and would not cause additional impacts to the
wetlands. Alternative flood control strategies, such as raising the existing dam
elevation, were considered but found to not be practical due to the potential
impacts on adjacent landowners.
Site 2 - Northshore FrinVe Wetlands
0.03 acres of current fringe wetlands are . located around Northshore Lake as
shown in Figures 4a and 4b. These wetlands have formed in the flatter portions of
the lake margin where water is shallow enough to allow colonization by
hydrophytic plants. Lowering the water level will impact all of these wetlands.
The dredging of the lake will maintain the current lake margins by creating a
shallow shelf along the edge of the lake. Fringe wetlands are likely to reform in
areas that supply suitable depth.
As stated above, avoidance of the water level decrease was examined but deemed
not practical due to flood control and spillway capacity issues necessary to
comply with the NC Dam Safety Act. Therefore, the impacts to the fringe
wetlands are necessary. Minimization of these impacts is being achieved through
the dredging of adjacent shallow waters to maintain the current lake banks and
create shelves along the shore. This will allow for the natural reestablishment of
fringe wetlands in suitable locations around the perimeter of the lake.
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Site 3 - Northshore Dam and Spillway
Page 6 of 15
The construction of the Northshore spillway device, shown in Figure 6b, will
impact approximately 0.08 acres of open waters. No additional stream channel
will be impacted by the rehabilitation of the existing spillway downstream of the
dam. This stream channel is currently concrete and rock lined. This material will
be removed and replaced with proper materials. During construction, the stream
will be diverted around the current channel through pipes, preferably via gravity
flow.
Avoidance of this impact was deemed impractical due to the high flood hazard
conditions, the current state of the spillway, and lack of compliance with the NC
Dam Safety Act. The enlarged weir will remove some open water, but is
necessary to control the flows entering the spillway and reduce downstream
velocities and flooding potential. The current spillway is cracked and a portion of
the base flow is bypassing the spillway through voids underneath. This would
eventually lead to the failure of the spillway and degradation of the downstream
channel. The spillway length has been limited to not cause additional impacts to
the stream channel. The leveling of the dam will not impact the stream or open
water.
Site 4 - Brentwood Today Eastern Tributary
Although sediment is being controlled along the main stem lakes and stream
through the sediment pool on Northshore Lake, there is a significant amount of
the overall watershed (31%) that enters Brentwood Today Lake through an
eastern tributary that is piped under the Mini-City area along Capital Boulevard.
The sediment load in this tributary has created headwater wetlands similar to
those at the upper end of both lakes. In order to reduce this sediment load and
minimize further filling of the Brentwood Today Lake, a sediment pool is
proposed on this tributary. Construction of this pool will impact 0.07 acres of this
wetland area. The remaining wetland and the wetlands at the upper end of the
lake will not be impacted. In addition, 80 feet of perennial stream channel of the
eastern tributary will be impacted by construction of the sediment pool (Figure
7b).
Avoidance of this impact was considered, but it was not deemed practical due to
the sediment load currently produced from the watershed to the east of Brentwood
Today. As discussed above, an offline forebay would not control base flow
sediment load and would be greatly reduced in size. In addition, it would likely
involve additional taking of properties.
Site 5 - Brentwood Today Dam and Spillway
The 50 feet of remaining spillway at the Brentwood Today Lake is progressively
collapsing and the banks of the stream channel are sloughing in. The original
spillway length below the dam was approximately 200 feet. The proposed
spillway length is 100 feet, which yields an additional impact of 50 linear feet of
Northshore & Brentwood Today Lakes
4041401 Pennit Application Narrative
Page 7of15
perennial stream channel when compared to current conditions, but is within the
original footprint of the 200' spillway. The current conditions of this stream
channel, and the impending failure of the remaining 50 feet of the spillway,
prevent any other alternative solution besides draining the lake. The inlet
structure will impact an additional 0.04 acres of open waters.
Avoidance of the spillway improvements was unavoidable due to the state of the
current structure. Of the original 200 foot spillway, only 50 feet remain (and
sections are continuing to collapse). The proposed length of the spillway is
enough to pass the required flows (based on Dam Safety Act requirements) and
tie into the existing stream channel while reducing velocities of the outflow so as
to minimize potential for downstream degradation.
Mitigation
The original concept for compensatory mitigation for this project was to use the enhanced
wetlands associated with the Northshore Lake (Figures 6a and 6b) to offset the
unavoidable wetland losses. In an October 5, 2004 pre-application meeting with the
USACE, it was determined that these wetlands could not be used as compensatory
mitigation since they are a component of a stormwater facility. This was concurred by
the EPA in email correspondence on February 7, 2005. It was agreed in the pre-
application meeting with the USACE that a proposal would be considered to not require
mitigation for impacts if functional replacement could be proven for the project. DWQ
401 Certification Unit staff tentatively agreed to a similar approach in an October 22,
2004 pre-application meeting. Therefore, the following mitigation section is designed to
justify the waving of compensatory mitigation for the proposed impacts due to the
functional replacement of the project components.
Wetland Functions
The impacted wetlands are discussed below by category of wetland functions as
described in the "Guidance for Rating the Values of Wetlands in North Carolina"
published by NCDENR.
Water Storage
The current wetland areas consist of bars of sediment transported downstream and
deposited at the inlet of the lakes. Little micro topographic relief is present in
these wetlands and therefore their water storage capacity during flood events is
low. As these wetlands have formed above the normal pool elevation of the lakes,
they have actually decreased the amount of flood storage provided by the
freeboard of the lakes. The increase in flood storage capacity created by the drop
in water level of Northshore Lake will greatly increase flood storage capacity of
the entire system and therefore offset any loss of flood storage retention in the
wetland areas.
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Bank/Shoreline Stabilization
Page 8 of 15
The current wetlands consist of fine silts and sands deposited in the upper end of
the lakes. These areas are constantly shifting and provide little stabilization of the
stream banks. Vegetation in much of these areas is limited to herbaceous species
such as Jewelweed (linpatiens capensis) that provide little stabilization.
Reduction of the water level in Northshore, along with the dredging of sediments
in both lakes, will remove most of these sediments. The creation of the sediment
pools prior to these wetland areas will help to reduce the erosive velocities and
scour potential of the streams and therefore will not decrease the bank
stabilization of the system. Currently, the stream channels immediately upstream
of the open water are pooled, channelized, and relatively incised. The channel
below the Brentwood Today dam is currently caving in and causing additional
water quality problems. Overall, the project will reduce downstream erosion
potential by controlling flooding and reducing velocities downstream of the
spillways. This reduction in erosion and stabilization of the currently eroding
banks adjacent to the spillway will help mitigate the minor stream impacts
associated with the project. The current conditions of the streams, specifically the
stream below Brentwood Today, would more than mitigate for the loss of this
function.
Pollutant Removal
The current wetlands do provide some pollutant removal for the incoming flows.
However, as described in the following text and supported in the attached
technical memoranda, pollutant removal efficiencies will be increased throughout
the watershed as a result of this project. This was one of the primary purposes of
this project.
Examination of the New Hope Tributary (including Northshore and Brentwood
Today Lakes) as the system of treatment facilities for the entire watershed
provides a comprehensive assessment of water quality. Table 2 integrates the
combined loadings from all five sub-watersheds studied (attached as Technical
Memorandum No. 4) and the trapping capacity of both lakes to yield a composite
load and overall removal efficiency from the system. These results are presented
in the last three columns of Table 2. The system is operating in the mid-range of
the removal efficiency for wet ponds, based on the initial assumptions of poor
removal capacity for the individual lakes. However, the main function of this
system simply operates to detain pollutants and does not facilitate the expedition
of these pollutants entirely out of the system. Nitrogen, phosphorus, and TSS
would be available for reintroduction into the system's downstream conveyance.
Northshore & Brentwood Today Lakes
4041401 Pertnit Application Narrative
Tahle 2: Comnarative Loading Analvsis
Page 9 of 15
Loadings to Total Loadings to
Trapped Load from
Loadings out of Overall
Constituent Beaman Brentwood &
the System
Brentwood Removal
Lake ' Northshore Efficiency
Total Nitrogen 3,872 13,320 4,124 9,196 31%
Total Phosphorus 1,215 1,400 787 613 56%
TSS 284,712 285,050 226,648 58,402 80%
Fecal Coliform N/A 4,540 850 3,690 19%
NOTES: Loadings are presented in Ibs/year except for fecal coliform, which are presented in colony forming units x
109/year; '- Data from Beaman Lake Embankment Rehabilitation report.
The initial assessment of total nitrogen removed by Northshore and Brentwood
appears to meet the 30 percent reduction requirement in nitrogen specified in the
Neuse River Rules. However, the City of Raleigh's Stormwater Management
Design Manual requires that the nitrogen load from new development not exceed
3.6 lbs/acre/year. This equates to approximately 2,700 lbs/year, which would
theoretically be the target loading out of Brentwood Lake if the two watersheds
were not already mostly built-out. This is a much smaller loading as compared to
the present loading of approximately 9,200 lbs/year out of Brentwood Today.
While the 2,700 lbs/year may not be a reasonable goal, it still emphasizes the need
for maximizing nitrogen control where possible.
Wildlife Habitat
The current wetlands are relatively small and provide little wildlife habitat. The
vegetation primarily consists of herbaceous species, with some younger saplings,
shrubs, and trees. The surrounding land use is almost completely built out and
provides little refuge for populations of wildlife. Potential cover is adequate only
in spotty areas, and is periodically cleared out by adjacent landowners. Mast
producing trees and other food sources are limited by this disturbance. The
project will remove some of the thin riparian buffer along the streams and lakes in
the area of the sediment pools. This will be mitigated by the replacement of
similar vegetation types and cover in the enhanced wetlands created by the
exposure of additional land surface when the Northshore Lake level is dropped.
Additional open water created by the dredging operations, along with the
establishment of littoral shelves and benches around the perimeter of Northshore
Lake will increase waterfowl habitat.
Aquatic Life
Currently, the aquatic habitat of the two lakes and connecting streams is in poor
condition. As described above, the lakes have gradually filled in with sediment
and therefore removed most of the deepwater habitat in these systems.
Approximately 30% of Northshore Lake and 50% of Brentwood Today are less
than 1 foot deep. This has created conditions that promote the growth of algae
and invasive aquatic plants that are currently choking the system. The dredging
of the lakes and control of the sediment load coming downstream will greatly
enhance the aquatic habitat of the lakes. The lowering of the Northshore water
level will allow the stream below Comstock Road to flow rather than be
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Page 10 of 15
inundated most of the time. Based on interviews with local residents, fish
populations in both lakes have seriously declined in the last several decades. The
aquatic benches created by the dredging operations will add aquatic habitat by
providing shallow water refuge adjacent to deeper water habitat. The construction
of the spillways will not change the current impediments to fish passage. The
overall project will improve the quality of the aquatic habitat in both the lakes.
Recreation and Education
Recreation opportunities, which were originally quite high for these lakes, have
drastically decreased over the last several decades. Fishing has declined due to
the decrease in fish populations associated with the poor water quality and
sedimentation. Boating opportunities have also declined as significant portions of
these lakes have become inaccessible by watercraft. Several docks are currently
surrounded by wetlands or water less than 1 foot deep. The project will increase
both these functions to a great extent. Fish habitat will be increased, and over
time fishing opportunities should likewise increase. Boat access will be enhanced
through the dredging of the lakes. While some areas without current open water
access will not change (such as the upper portion of Brentwood Today),
landowners with access to open water will have that access enhanced through the
dredging of channels and deepening of the lakes.
Stream Mitigation
Stream impacts associated with this project are limited to 390 linear feet of
perennial stream. Current stream channel degradation along the old spillway of
Brentwood Today Lake will be repaired during the construction of the spillway,
and downstream impacts from sedimentation and erosive velocities will be
reduced by the proposed enhancements and rehabilitation. Since the stream
channels along the spillways of these lakes have already been impacted, only
additional stream channel impacts have been included in these calculations. Any
channel impacts occurring at the upper reaches of each lake are impacting open
water that falls within the streambanks - these channels are not functioning as
streams but as open water conveyances. Some grade control points may be
established in the exposed stream channels to prevent head cutting as needed.
Therefore, no stream mitigation is being proposed for this project. The overall
watershed and water quality improvements associated with this project provide
sufficient mitigation for the minor amounts of stream impacts.
Based on the overall assessment of the functions described above, each wetland
function is at minimum replaced and, more frequently, enhanced by the project.
Stream impacts and enhancements are largely offset by the primary goal of water
quality improvements and the rehabilitation of the dams. The overall goals of
flood control and water quality, along with the current severely degraded state of
these lakes, provides mitigation for these functions through an alternative delivery
process rather than traditional compensatory mitigation. It is therefore proposed
that no formal compensatory mitigation be required for the impacts associated
with this project.
NonAshore & Brennvood Today Ickes
4041401 Permit Application Narrative
Neuse Buffer Impacts and Mitigation Requirements
Page 11 of 15
Figures 6a, 6b, 7a, and 7b present the current riparian buffers within the project area
under jurisdiction of the Neuse River Riparian Buffer Rules. The proposed plan will
impact 1.95 acres of the total 12 acres of buffers currently surrounding the lakes. These
impacts stem primarily from spillway improvements and sediment pool construction.
The impacts related to the rehabilitation of the dams and spillways are exempt under the
current rules. Since the dredging operation will retain the current lake limits by creating
benches along the shores, no permanent loss of riparian buffers are associated with this
activity. The construction of the sediment pools will require impacts to 0.84 acres of
riparian buffers. These impacts do not create new impervious surfaces.
Protected Species
Plants and animals classified as Endangered or Threatened by the U.S. Fish and Wildlife
Service (USFWS) are protected under provisions of Section 7 and Section 9 of the
Endangered Species Act of 1973, as amended. Table 9 presents USFWS list of federally
protected species for Wake County, North Carolina as of February 25, 2003.
Table 3: Federal Listed Protected Species for Wake County, NC
Scientific Name Common Name Federal Status
Haliaeetus leucocephalus Bald eagle Threatened-Proposed
for Delistin
Picoides borealis Red-cockaded woodpecker (RCW) Endangered
Alasmidonta heterodon Dwarf wedgemussel Endangered
Rhus nzichalixii Michaux's sumac Endangered
Limited potential habitat exists on-site for each species (Bald eagle - open water; RCW -
mature pines; Dwarf wedgemussel - perennial streams; Michaux's sumac - regularly
maintained edge habitat). Prior to construction, surveys will be performed for each
species as requested by the permitting agencies.
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Photographs
4 f'
.

/t

Page 12 of 15
Upper end of Northshore Lake
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
[ '1 If
r'
Page 13 of 15
Top of Northshore Lake spillway
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative
Brentwood Today Lake, looking upstream
Brentwood Today dam spillway, looking dowt
September
i .;
Page 14 of 15
spillway (as of
Northshore & Brentwood Today Lakes
4041401 Permit Application Narrative

Post-storm destruction below Brentwood Today spillway due to
(April 2004, along the eastern streambank and -20' downstri

Approximate former location of Brentwood Today spillway, no
the progressively collapsing end of the spillway
erosion and
Fexisting sp
above
Page 15 of 15
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a

Jamison, John R.
From: [e-mail]
Sent: Monday, February 07, 2005 3:00 PM
To: May, Philip
Cc: [e-mail]
Subject: RE: Forebay Issues
Phil,
Just wanted to send you a quick reply to your forebay question before I head out on work
travel. It is my opinion that the forebays will not be an issue if the permit decision is
made to convert these ponds to stormwater treatment systems and appropriate mitigation is
provided for this loss of "waters" since they will no longer be jurisdictional waters of
the US. I also spoke to EPA's regional stormwater expert and she concurred with this. We
would caution that the forebays should not be constructed to a depth as to allow them to
become anoxic and/or to thermally stratify. It appears this is not the case with your
design which indicates forebays will be constructed 2 to 4 feet in depth. Most literature
recommends an average depth of wet ponds to be in the range of 3 to 9 feet. If you are
wanting to go deeper than that we would like to further discuss this with you. We would
recommend that you might want to make your forebays a little deeper than you are proposing
to allow for some accumulation of coarse material between scheduled maintenance. This
would help prevent resuspension of particulates during larger events.
One concern I did have when I reviewed your website is that it appears you are proposing
wetlands between the forebay and the larger pond to be used as mitigation for project
impacts. This is something we would want to discuss with you and Jennifer since it is our
position that mitigation credit can not be given for an area that is not jurisdictional
which would apply to these ponds if they are converted to storm water treatment systems.
Shallow wetland shelves are an important component of a good pond treatment system so we
would encourage their construction but can not recommend they be used to provide
mitigation credit.
Let me know if I can be of any more assistance.
getting back to you on the forebay issue.
Once again, sorry for the delay in
Becky Fox
Wetland Regulatory Section
USEPA
Phone: [phone]
Email: [e-mail]
"May, Philip" <[e-mail]> wrote on 01/24/2005 03:08:59 PM:
> Thanks Becky - I understand how your schedule must be - especially
around the
> holidays.
> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]]
> Sent: Monday, January 24, 2005 3:00 PM
> To: May, Philip
> Subject: RE: Forebay Issues
> Thanks for the reminder Phil. Things have been crazy since we
communicated
> in Nov and I have not been to Raleigh since then but this project has
been
> floating about in the back recesses of my mind and I knew that I owed
you
> some comments. I will try to get back with you sometime either this
week or
> early next week.
i
> Becky Fox
> Wetland Regulatory Section
> USEPA
> Phone: [phone]
> Email: [e-mail]
> "May, Philip"
> <Phil.May@hdrinc. To: Rebecca
> Fox/R4/USEPA/US@EPA
> com> cc:
> Subject: RE: Forebay
Issues
> 01/24/2005 02:33
> PM
> Becky
> I just wanted to let you know that the City is asking us to prepare
and
> submit our permit prior to our last meeting with the public. If you
have any
> comments on the forebay issue in the next couple of weeks, please let
me
> know. Otherwise, we should be submitting the IP in mid-February and
will
> respond to any comments during the review of the permit.
> Thanks
> Phil
> -----Original Message-----
> From: May, Philip
> Sent: Monday, November 29, 2004 11:32 AM
> To: '[e-mail]'
> Subject: RE: Forebay Issues
> Becky,
> The forebays are planned for the upstream portions of the ponds, which
have
> filled in over the last couple of decades. There are existing
wetlands in
> these areas, however the planned change in water level (to alleviate
flooding
> below the dam by increasing flood storage) would likely drain these
areas.
> We have a web site for the project - www.raleighlakes.com - this has a
> summary of the information provided in a couple of public meetings.
The web
> site is probably the easiest way to get you information - it has a
couple of
2
> powerpoint presentations used in the first community meetings (click
on "more
> information" at each of the community meetings). If you need any more
> information please let me know.
> At this point we have come up with three alternative plans for each of
the
> two lakes and proposed one of each as the recommended plan, but we
would like
> to incorporate all the regulatory input we can get prior to a last
public
> meeting on the final recommended plan. I would like to know the
feasibility
> of using forebays on the project prior to that. I doubt this meeting
will
> happen before January.
> Please call me at your convenience if you have any questions or need
me to
> send you more information.
> Thanks
> Phil
> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]]
> Sent: Monday, November 29, 2004 10:05 AM
> To: May, Philip
> Subject: Re: Forebay Issues
> Phil,
> Will the forebays be constructed in the upstream portion of the ponds
to be
> rehabilitated or will the forebays be constructed upstream of the
current
> dams? If you could send me some info that would be great. You could
send
> smaller files (without pictures and maps electronically) or mail
larger files
> to:
> 1349 Firefly Road
> Whittier, NC 28789
> After reviewing the info I will contact you about either meeting or
phone
> conference to further discuss the projects. What is your time frame?
> Thanks,
> Becky Fox
> Wetland Regulatory Section
> USEPA
> Phone: [phone]
> Email: [e-mail]
> "May, Philip"
> <Phil.May@hdrinc. To: Rebecca
> Fox/R4/USEPA/US@EPA
> com> cc:
> Subject: Forebay
3
Issues
> 11/29/2004 09:49
> AM
> Becky,
> On John Dorney's advice, I am contacting you in regard to the use of
forebays
> on a project involving the rehabilitation of a couple of dams on small
ponds
> in the City of Raleigh. The City is studying these lakes with the
intention
> of repairing the dams or spillways, and adjusting the water levels
(with some
> dredging) to provide additional flood storage and water quality
improvements.
> As a part of the plan we are developing, we have included the use of
deep
> pools or forebays at the upper end of these lakes. I was hesitant to
include
> this and warned our engineers and the City that in-line forebays could
be an
> issues, but the Corps (Jennifer Burdette) said that in conversations
with you
> the forebay issue was not really a problem since the entire lake would
serve
> a stormwater function. John Dorney's take on this is different and he
> therefore recommended we discuss this directly with you.
> I would be happy to send you some information to review. We would
also like
> to meet with you when it is convenient to discuss the project. Do you
have
> any time on upcoming trips to Raleigh to meet?
> Thanks
> Phil
> Philip May
> HDR Engineering, Inc. of the Carolinas
> 3733 National Drive, Suite 207
> Raleigh, NC 27612
> [phone]
> [e-mail]
4
TECHNICAL MEMORANDUM NO. 4
Water Quality Evaluation of Conceptual Plans
NORTHSHORE LAKE AND
BRENTWOOD TODAY LACE
DAM REHABILITATION PROJECTS
CITY OF RALEIGH, NORTH CAROLINA
February 22, 2005
Prepared By:
fua--l
HDR Engineering, Inc. of the Carolinas
HDR Project No. 10913-9154
TABLE OF CONTENTS
SECTION
PAGE
1.0 INTRODUCTION ............................................................................................................................1
1.1 Overall Project Description ..................................................................................................1
1.2 Water Quality Component ...................................................................................................1
1.3 Preliminary Water Quality Assessment Methodology ........................................................2
2.0 WATER QUALITY EVALUATION AND MODELING ...........................................................3
2.1 Purpose .................................................................................................................................3
2.2 Model Selection ...................................................................................................................3
3.0 MODEL DEVELOPMENT ............................................................................................................5
3.1 Future Land Use Analysis ....................................................................................................5
3.2 Watershed Delineation ..... ....................................................................................................5
3.3 Hydrologic Parameters .........................................................................................................6
3.4 Water Quality Parameters ....................................................................................................7
3.5 Device Parameters ............ ...................................................................................................8
3.6 Meteorological Data .............................................................................................................8
3.7 Calibration ............................................................................................................................9
4.0 MODEL EXECUTION ....................................................................................................................9
4.1 Alternatives Development ...................................................................................................9
4.2 Results and Findings ..........................................................................................................13
5.0 MODEL EVALUATION ...............................................................................................................18
5.1 Continuity Errors ................................................................................................................18
5.2 Sensitivity Analysis ............................................................................................................18
6.0 CONCLUSION AND DISCUSSION ...........................................................................................19
7.0 REFERENCES ...............................................................................................................................21
LIST OF TABLES
3-1 Event Mean Concentrations (EMC) for Selected Pollutants ..............................................................8
4-1 Comparison of Pollutant Loadings from the Preliminary Assessment and the Model .................... 13
4-2 Overall TSS Removal Efficiency (%) .............................................................................................. 14
4-3 Overall TPP Removal Efficiency (%) .............................................................................................. 15
4-4 Overall TKN Removal Efficiency (Vo) ............................................................................................. 16
4-5 TSS Loading (lbs) Discharge out of Brentwood Today Lake .......................................................... 17
4-6 TP Loading (lbs) Discharged out of Brentwood Today Lake .......................................................... 17
4-7 TKN Loading (lbs) Discharged out of Brentwood Today Lake ....................................................... 17
LIST OF FIGURES
1-1 Project Site Location ...........................................................................................................................2
4-1 Graphical Depictions of the Modeled Networks for the Alternatives ..............................................12
4-2 Removal Efficiency (%) for Discrete Particles .................................................................................15
1Vater Quality Evaluation i February 2005
of Conceptual Plans
SECTION 1.0 - INTRODUCTION
1.1 Overall Project Description
There are a series of four lakes along the New Hope tributary to Marsh and Crabtree Creeks: an
unnamed lake, Northshore, Brentwood Today, and Beaman. The unnamed lake and Beaman are
presently not included within the scope of this Project. The dam at Beaman Lake was breached
several years ago and is currently under reconstruction, restoring the dam embankment and
installing features to improve water quality.
This Project includes Northshore and Brentwood Today Lakes, which are located in the City of
Raleigh (City) near New Hope Church Road and west of U.S. 1 as shown in Figure 1-1. The
dams at both Lakes were identified as small, high hazard dams in the Titan Atlantic Report dated
July 20, 2004. Furthermore, the spillways at both Lakes have been a concern for over 20 years.
The dams have been overtopped several times in recent years, causing flooding in the
surrounding residential area. There is a concern that New Hope Church Road, located just
downstream of Northshore Dam, may wash out during an overtopping event.
The purpose of this project is to evaluate both Northshore and Brentwood Today Lakes for dam
safety concerns and water quality improvements. Three different aspects will be evaluated:
? Dam safety and flood attenuation,
? Water quality improvements, and
? A composite plan integrating dam safety and water quality.
The purpose of this Technical Memorandum (TM) is to provide an evaluation of water quality
for these three alternatives. Additionally, a discussion of the results of this evaluation along with
baseline conditions derived in previous assessments and the differing aspects of the two
approaches will be presented.
1.2 Water Quality Component
Northshore and Brentwood Today Lakes are classified as C Nutrient Sensitive Waters (NSW) by
the North Carolina Division of Water Quality (NCDWQ). Both Lakes have not yet been rated
for their level of support for this designated use. NSW are less likely to assimilate additional
loadings of nutrients, primarily nitrogen and phosphorus, without detrimental effects on the
water quality. The lake's inclusion as NSW is likely due to their watershed being part of the
Lower Neuse River Basin.
Water Quality Evaluation February 2005
of Conceptual Plans
Northshore and Brentwood Today Lakes have been significantly impacted in the last 20 years.
During this time, the watershed has seen significant commercial.and high density residential
development. The most notable commercial development was the construction of "Mini City"
off Capital Boulevard. With this development has come the disturbance of land and an increase
in impervious area throughout the watershed. The increase in impervious surface increases peak
flows during storm events may have resulted in erosion of unstable stream banks. In addition,
stormwater has transported sediment to these Lakes. This is evident by the unconsolidated soil
deposition found in the mouths of the contributing streams to Northshore and Brentwood Today
Lakes. It is also likely that sediment is carrying a host of urban pollutants to these Lakes, such as
nutrients, metals, organic matter, and fecal coliform.
Eutrophication is also apparent in both Northshore and Brentwood Today Lakes. The abundance
of sediments and solids in stormwater, likely transporting nutrients, as well as dissolved nutrients
found in fertilizers typically used in residential areas have also been conveyed to these Lakes.
Their presence in excess quantity has lead to the excessive growth of phytoplankton or floating
algae that is currently seen in the two Lakes. As the excessive algal biomass dies, it consumes
the bulk of dissolved oxygen that supports life Other contributing sources to the eutrophication
include the waterfowl nesting at the Lakes, domestic pet waste, and possible failing sanitary
sewer lines or sewer overflows.
Bacterial contamination of the Northshore and Brentwood Today Lakes is a prominent concern
as these Lakes are sources of recreation for the adjacent property owners. The Lakes are Class C
and therefore should support the designated uses of secondary contact recreation such as boating
and wading. Visual inspection of the area indicates that some sources of bacterial contamination
(i.e., waterfowl excreta) have direct contact with the Lakes. These Lakes are typical of the urban
setting, in that they likely exhibit fecal coliform levels that do not support the C waters
classification.
1.3 Preliminary Water Quality Assessment Methodology
A preliminary water quality assessment was performed early in the project and documented in
Technical Memorandum #2 Water Quality Assessment (TM #2). The objective of that water
quality assessment was to evaluate the level and location of pollutant stress being delivered to
these Lakes. That assessment assisted in determining suitable design elements and their location
as well as providing a preliminary baseline for design efficiency. The methodology employed
for the analysis utilized literature values of pollutant export coefficients and geographic land use
data to generate loadings for specific sub-watersheds. That cursory view of watershed conditions
was beneficial in determining a more detailed approach to be used in the final water quality
evaluation of the Project alternatives.
Water Quality Evaluation 2 February 2005
of Conceptual Plans
SECTION 2.0 - WATER QUALITY EVALUATION AND MODELING
2.1 Purpose
The purpose of this effort and TM are to provide an evaluation of several alternatives with
respect to the improvement of water quality downstream and within the Lakes' system. It is
difficult to translate water quality goals (i.e., concentration and removal efficiency) into tangible
water quality benefits due to the high variability of natural processes and the existence of
unaccountable interactions. However, assuming that this variability is inherent and global, a
relative evaluation of alternatives with similar base conditions and processes will yield a similar
relative response in water quality benefit. An evaluation performed through modeling and sound
interpretation of results will provide this relative assessment.
Water quality models can be used for the prediction of loading, transport, and control of
pollutants. The application of a water quality model will expand upon the empirical effort
accomplished in the TM #2 by incorporating representative data with the simulation of the
existing physical processes. The use of a water quality model will further the assessment in the
following ways:
¦ Provide pollutant loading based on studied pollutant development and hydrologic interaction.
¦ Routing and transport of flow and pollutants through continuous water and mass balance.
¦ Simulation of physical pollutant removal processes and their efficiency over varied
flow/volume regimes.
2.2 Model Selection
The type of water quality model required to fulfill the aforementioned objectives lies within the
range of mid-level models. These models compromise the empiricism of the simple methods
and the complexity of detailed models driven by parameter intensive, mechanistic processes
(EPA, 1999). When fully calibrated and inputed with site-specific parameters they can provide
an appropriate means of prediction. Despite limitations on data availability, these models still
provide decision makers the ability to select watershed-level planning solutions based on relative
comparisons. PS-Urban Catchment Model (PS-UCM), developed for IEP, Inc and the
Narragansett Bay Project by William W. Walker, Jr., Ph.D, was selected for this application
based on these needs. The relative ease of parameter estimation and input and HDR's familiarity
Water Quality Evaluation: 3 February 2005
of Conceptual Plans
of the model were factors in its selection. Additional strengths of the model for use in this
Project are listed below (EPA, 1992):
¦ Developed and calibrated for use within small, urban watersheds.
¦ Distributed with particle and water quality pollutant distribution data calibrated against
Nationwide Urban Runoff Program (NURP) data.
¦ Simulation of particle accumulation, decay, and wash-off dynamics.
¦ Sources can be characterized as single, continuous, or diffuse release.
¦ Continuous and storm event simulation.
¦ Provides for the inclusion of several structural Best Management Practices (BMPs): wetland,
detention ponds (dry, wet, and extended), infiltration basins, and swales/buffers.
¦ Hydrologic and water quality output can be evaluated at discrete model components.
¦ Relative evaluation of pollutant loadings, outflow concentrations, and BMP removal
efficiencies.
P8-UCM like many other urban runoff models has some limitations. The following is a brief
listing of limitations of this model (EPA, 1992):
¦ Lack of site specific calibration data limits the model in absolute prediction of pollutants
loads and concentrations.
¦ Primary pollutant removal process is sedimentation and filtration.
¦ Does not simulate in-stream transport and transformation processes for pollutants.
¦ Watershed lag is not simulated.
However, P8-UCM can be a scalable model, in the sense that many of these limitations can be
overcome with site-specific water quality data and representation of physical, chemical, and
biological processes through alternative parameterization.
Water Quality Evaluation 4 February 2005
of Conceptual Plans
SECTION 3.0 - MODEL DEVELOPMENT
3.1 Future Land Use Analysis
A future build-out analysis was performed by Watershed Concepts for the entire Marsh Creek
Basin as part of a hydrologic model. Field inspections of the Northshore and Brentwood Today
Lakes watersheds suggest that current land use conditions are near, if not at, future build-out
conditions. Performing another future build-out analysis with the same base data would yield
similar results. Better value of this analysis would be to evaluate the base data against
orthophotography and field inspections performed while collecting storm sewer inventory. It is
likely that due to the breadth of that previous future build-out analysis and the intent of its end
product, the data was not site checked entirely. With the limited focus of this project the existing
land use and future land use conditions can be individually verified. This is important in
determining hydrologic and water quality parameters for the water quality modeling. The
findings of this evaluation show that the current open space was under estimated by 50 acres.
Much of the land was either characterized as medium residential or industrial. Future build-out
analysis of the open space portion would likely result in some additional commercial land use
but remain mostly open space, as the identified parcels are small and isolated. Due to the small
percentage of mischaracterized land (approximately 6 percent of total watershed area) and its
distribution across the watershed, it is likely this difference will have little effect on
parameterization for this evaluation.
3.2 Watershed Delineation
Watershed delineations were first performed in TM #2 for the purposing of identifying
magnitude and source location of pollutant loads into the Lakes. These same delineations proved
to be sufficient for application in the water quality model and this evaluation. The delineations
were generated using a variety of data detailed below:
¦ City of Raleigh topographic and planimetric CAD data (2000)
¦ NCGIA/DWQ Hydrography (1998)
¦ HDR Storm Sewer Inventory (2004)
P8-UCM emphasizes the location of incoming flows for the proper mixing of flows and
concentrations. Watershed delineations were created to accurately represent the appropriate
routing of flows through existing and proposed water quality controls (sediment pools, wetlands,
Water Quality Evaluation 5 February 2005
of Conceptual Plans
and ponds). The Northshore Lake drainage was delineated into three sub-watersheds called
Upper, Middle, and Lower. The Upper sub-watershed includes the area where the generated
runoff would pass through the smaller unnamed pond south of Calvary Road. The Middle sub-
watershed includes the area where the generated runoff would enter Northshore Lake as a stream
at the mouth of the lake. The final sub-watershed called Lower includes areas draining directly to
the body of Northshore Lake. The Brentwood Today Lake follows the same logic. It is
delineated into two sub-watersheds called Main and Tributary. They represent the areas where
generated stormwater enter the head and body laterally of Brentwood Today Lake and as a side
tributary, respectively.
3.3 Hydrologic Parameters
P8-UCM estimates runoff from precipitation data and hydrologic parameters. The model
evaluates runoff from pervious and impervious areas separately. Runoff for the pervious areas is
computed using the SCS curve number method. These values are adjusted internally based on
antecedent moisture conditions (Haith and Shoemaker, 1987). Since, P8-UCM is mainly applied
in urban settings; this method proves to be a sufficient approach due to its simple
parameterization of pervious conditions that account for only a minor component of the total
urban runoff. The required parameters for pervious runoff generation are SCS curve numbers
representing "open space" land use and respective hydrologic soil groups (SCS, 1986).
Impervious runoff is computed from the difference of cumulative rainfall and depression storage.
Runoff initiates as cumulative rainfall depth exceeds a user-specified depression storage depth.
After this point, runoff equals rainfall intensity for the impervious fraction of the watershed. The
required parameters for impervious runoff generation include depression storage values and
impervious fractions. Depression storage values were obtained from literature values
categorized by land uses (Wright-McLaughin Engineers, 1969) and impervious fractions were
obtained from SCS curve number descriptions (SCS, 1986). The runoff from pervious and
impervious areas is combined and routed to the downstream device with no lag.
The future build-out land use data, described in more detail in Section 3.1 Future Land Use
Analysis, and NRCS digital soil surveys were used to create areas for parameterization. This
hydrologic data was input into P8-UCM for individual land uses within the watershed
delineations. This was done so that future application of the model could be calibrated for
pollutant event mean concentrations if desired. Depression storage and impervious fractions were
input wholly for their respective land use. Only curve numbers for pervious areas were
computed on a composite area average for their hydrologic soil group.
Water Quality Evaluation 6 February 2005
of Conceptual Plans
3.4 Water Quality Parameters
The generation of water quality pollutant loads and runoff concentrations for P8-UCM is based
on the dynamics of particle accumulation and wash-off principles as well as pollutant mass
distribution within those particles. The first component of the quality representation is the
parameterization of particle classes. P8-UCM allows for the distribution of five particle classes.
For each particle class, particle generation parameters are input for both impervious and pervious
segments of a watershed. Impervious input parameters include accumulation rates, decay rates,
wash-off exponents and coefficients, and street sweeping efficiency (when applicable).
Additionally, runoff concentrations can be provided in favor of accumulation and wash-off
dynamics. On the pervious portion of the watershed, particle generation is based on input
parameters of pollutant concentration for the individual particle classes. Particle removal
dynamics are quantified within this component of the P8-UCM model as well. Removal
dynamics are characterized for individual particle classes by settling velocity and filtration
efficiency through pervious mediums.
The second component of the water quality representation within P8-UCM provides for the
distribution of pollutants among the particle classes. Pollutant mass per particle class is the input
parameter. Since multiple pollutants can be modeled with a single particle distribution, scale
factors exist for calibration if desired.
P8-UCM includes several particle distribution data files that can be used for default parameters
when particle and pollutant mass data is not available. The majority of this default data was
calibrated to represent the results obtained in the Nationwide Urban Runoff Program (NURP).
The particle distribution file titled nurp50.par was used in this evaluation. The file contains five
particles classes that are based on calibration of runoff concentration and settling velocity
distributions representative of median sites (i.e., particle class P10 = 10th percentile). Distribution
of the pollutant mass among particle classes is based upon results of direct runoff concentration,
settling column tests, and typical removal efficiencies of treatment devices (Walker, 1990). This
particle distribution file contains accumulation/wash-off parameters and settling velocities for
four non-dissolved particle classes. The fifth particle class was developed to simulate the non-
settling, dissolved particles. The file also contains mass distributions for a variety of urban
pollutants such as particulates, nutrients, heavy metals, and hydrocarbons. Attention will be
primarily focused on total suspended solids (TSS), total phosphorus (TP), and total Kjeldahl
nitrogen (TKN). Table 3-1 displays the calibrated event mean concentrations per median data
sites of NURP.
Water Quality Evaluation 7 February 2005
of Conceptual Plans
Table 3-1
Event Mean Concentrations (EMC) for Selected Pollutants
Total suspended solids 100.0
Total phosphorus 0.33
Total Kjeldahl nitrogen 1.5
3.5 Device Parameters
Devices provide for the hydraulic routing of runoff and areas for pollutant removal. P8-UCM
utilizes a variety of devices such as an infiltration basin, swale/buffer, flow splitter, and aquifer;
however, this assessment will only require the use of a detention pond, a general device, and a
pipe/manhole. The detention pond can be used as a device with a permanent pool and a normal
outlet that can be quantified by a single weir and/or collection of orifices. The required input
data for detention pond devices include surface area and volume quantities for permanent and
flood pool levels. The normal outlet that drains only the flood pool requires weir and orifice
dimensions and coefficients. Devices with more complex outlet configurations can be modeled
with the general device which requires a stage-surface area-discharge relationship for its volume
and outlet data. Both these devices also possess a particle removal scale factor. This value is
typically z 1 but can be adjusted higher or lower for the response of the device due to decreases
or increases in hydraulic residence time. The pipe/manhole device is useful for mixing two or
more incoming flows before being routed onto a removal device. Its only input parameter is a
time of concentration and the device provides for no pollutant removal. Pipe/manhole devices
can be used for delaying the hydrologic response of watersheds through the time of concentration
parameter. This approach is beneficial for the modeling of larger watersheds since the watershed
components route runoff with no lag.
3.6 Meteorological Data
Several meteorological parameters are required to balance hydrology for the watershed in P8-
UCM (i.e. precipitation, evapotranspiration, and percolation). Only precipitation and
evapotranspiration require meteorological data. Hydrologic events are driven by hourly
precipitation. Hourly rainfall data monitored at the Raleigh-Durham International Airport was
obtained from the National Climatic Data Center (NCDC) and used with the model. A SCS
Type II distribution (1-inch design storm precipitation file) is distributed with the model package
and also used in this effort. P8-UCM also calculates evapotranspiration using Hamon's Method
from monthly averages of vegetative cover, air temperatures, and hours of daylight (Hamon,
1961). Daylight hours and air temperatures were collected for the area from Summary of the Day
Water Quality Evaluation 8 February 2005
of Conceptual Plans
data also obtained from NCDC. Average monthly values for daylight and temperature were
calculated and inputted. Default data was used for vegetative cover. The total evapotranspiration
calculated by this approach resulted in 29.1 inches/year.
3.7 Calibration
P8-UCM provides for hydrologic and water quality calibration through the use of many
calibration factors and a calibration utility. However, the project watershed and the New Hope
Creek tributary do not have any United States Geological Survey (USGS) gauging stations or
any other confident streamflow monitoring data. A hydrologic and water quality calibration may
not be warranted at this time since the focus of this effort is a relative comparison of alternatives.
However, if the direction of the model is to be a tool for detailed design assessment, collection of
calibration data would be beneficial.
SECTION 4.0 - MODEL EXECUTION
4.1 Alternatives Development
As previously mentioned in Section 1.1 Overall Project Description, this TM will focus on the
water quality benefit gain or loss of the three alternatives: dam safety and flood attenuation,
water quality improvements, and a composite plan integrating the two. Several factors were
considered in the development of these alternatives. Technical Memorandum #3 Conceptual
Plans delivers full detail of the alternatives for each respective lake and the factors for the use of
particular design elements. A summary follows providing representation of each alternative as it
was modeled in P8-UCM. A fourth scenario was developed to represent a situation where
Northshore and Brentwood Today Lakes were breached and return to natural streams.
Dana Safety and Flood Attenuation
The major enhancement to the Lakes for this alternative include dredging, water surface
elevation change (Northshore only), and improved outlet design. These enhancements provide
minor water quality improvement. The new discharge outlets suppress lower design flows thus
increasing hydraulic residence time for particle settling. The dredging of unconsolidated
sediment in the Lake will provide for a net removal of sediment, nutrients, and metals that have
been historically trapped. A net removal of these pollutants will prevent any re-introduction into
the system due to the mixing of high velocity flows with shallow, unconsolidated sediment
layers. The two lake systems were modeled as general devices as opposed to detention ponds due
to their complex weir configuration. The particle removal scale factor was reduced from 1.0 to
Water Quality Evaluation 9 February 2005
of Conceptual Plans
0.75 to incorporate the poor distribution of incoming flow at the headwater of the Northshore
Lake and the existence of channelized flow through the Northshore Lake (i.e., short-circuiting).
Removal scale factors less than 1.0 can be assumed to account for poor hydraulic design
(Walker, 1990). Figure 4-1 (on page 12) depicts the model's representation of the system for
this alternative.
Dater Quality Enhancements
The water quality improvement alternative utilizes a variety of design elements to ensure the
removal of a variety of pollutants as well as provide additional habitat that would promote the
well being of aquatic life. The improvements for water quality include dredging, water surface
elevation change, improved outlet design, sediment pools, variety of concentrated wetlands,
wetland shelving (Northshore only), and plunge pools for point source runoff discharges. These
improvements attempt to concentrate the settling of the largest particles at the headwaters of the
Lakes where removal of accumulated matter is more manageable. The wetlands are expected to
provide filtration of smaller particles but also promote the biological uptake and trapping of
nutrients. Both Lakes were modeled as a series of detention ponds for the sediment pool and
wetlands. Wetlands were differentiated from the sediment pools primarily by increasing the
particle removal scale factor to 3 to accommodate for additional removal of TSS and TP.
Studies performed using P8-UCM relating detention ponds vegetated with macrophytes to
particle removal factors exhibited scale factors of 2 to 3 for TSS and 3 to 6 for TP to account for
z5 to 30 percent removal (Phillips & Goyen, 1987; Lawrence, 1986). The remaining open water
area of the Lakes was modeled as a separate general device. The wetland shelves and plunge
pools were not included as model elements because they are minor in size and lack definable
continuity with the rest of the system. Figure 4-1 depicts the model's representation of the
system for this alternative.
Recommended
The Recommended alternative combines many of the aspects of the Dam Safety alternative with
some water quality enhancements. Whereas the first two alternatives have specific design
objectives, this alternative considers those objectives in addition to factors such as public
acceptance, constructability, maintainability, and economic value. The design elements for
Northshore are similar to the Water Quality Alternative. However, headwater wetlands exists in
a lower quantity and wetland shelving is limited to plunge pool areas. The volume of dredging
for this alternative is more in line to the Dam Safety alternative. For the Brentwood Today Lake,
the recommended alternative resembles the Dam Safety alternative with the addition of sediment
Water Quality Evaluation 10 February 2005
of Conceptual Plans
pools located at the headwaters of the lake and plunge pools at point source runoff discharges.
Both lake systems were modeled similarly to the Water Quality alternative except with a
reduction in the area of the wetlands at Northshore and exclusion of wetlands at Brentwood
Today Lake. Figure 4-1 depicts the model's representation of the system for this alternative.
No Lakes
The final scenario is a theoretical simulation of the natural drainage system under the future land
use. In this scenario, Northshore and Brentwood Today Lakes are replaced by streams. The No
Lakes scenario provides a baseline of current loadings, concentrations, removal efficiencies as if
the Lakes were never constructed.
Global Model Assumptions
In all alternatives, some general assumptions were made to simplify the assessment. These
assumptions are as follows:
¦ The unnamed lake south of Calvary Drive was conservatively modeled the same in all
alternatives. It was included since its efficiency is important in terms of overall efficiency of
the system.
¦ Stream reaches were modeled as pipe segments with time of concentrations estimated as the
travel time at a bank full event. Pipe segments do not account for any pollutant removal,
which P8-UCM does not have the capacity to model.
¦ Base flow was not simulated since calibration data was not available and land use did not
change from alternative to alternative (i.e., volume of base flow would not change). Base
flow simulation would have yielded minor differences in loadings and removal efficiency
since the particle data file used accounts for 100 percent filtration through the ground in four
of five particle classes and 90 percent for the fifth particle class.
¦ Each alternative was run for a statistically dry, average, and wet year and for the 1-inch Type
II SCS distribution design storm. The statistical years were developed from a 55-year record
of total precipitation values. The statistical wet and dry years were plus or minus one
standard deviation about the average, respectively.
Water Quality Evaluation 11 February 2005
of Conceptual Plans
DAM SAFETY AND FLOOD ATTENUATION
UPPER MIDDLE TRIBUTARY
LOWER l MAIN
UNNAMED
NORTHSHORE
BRENTWOOD
TODAY
WATER QUALITY IMPROVEMENTS TRIBUTARY
TINORTHS,HCORE
L
UNNAMED BRENTWOOD
TODAY
LOWER MAIN
UPPER MIDDLE
RECOMMENDED JBRENTWOOD
LOWER MAIN 0
0 0
DETENTION SEDIMENT WETLAND
WATERSHED POND POOL
Figure 4-1. Graphical depictions of the modeled networks in P8-UCM for the alternatives
Water Quality Evaluation 12 February 2005
of Conceptual Plans
UNNAMED
NORTHSHORE

4.2 Results and Findings
Several primary sets of data were retrieved from the model runs for analysis and discussion in
this section. The first set of data summarizes loadings to Northshore and Brentwood Today
Lakes from their respective watersheds. Table 4-1 displays these results and provides a
comparison of previously determined loadings from TM #2. The loadings from P8-UCM model
were developed from accumulation/wash-off dynamics of particle distributions based on NURP
data. Their export mass is a direct result of the interaction with continuous hydrologic events.
The loadings for the preliminary assessment are empirically based on studies relating land use to
storm event concentrations. The P8-UCM-based set of TSS loadings exceeds our previously
determined loadings primarily due to differences in EMCs. EMCs used in the preliminary
assessment ranged from 40-80 mg/L for TSS, while the NURP data supporting P8-UCM had a
TSS EMC of 100 mg/L. EMC's for both assessments were similar for TP and the results
reiterated that similarity. TKN, the predominant particulate form of nitrogen, is modeled in P8-
UCM since the primary removal mechanism of the model is settling. A direct comparison of TN
versus TKN loadings is not valid. However, the values have been provided below as a reference.
Table 4-1
Comparison of Pollutant Loadings front the Preliminaq Assessment and the Model
TSS 168,840 260,691 116,210 207,971
TP 840 833 560 667
TN/TKN 7,300(TN) 3,748(TKN) 6,020(TN) 3,002(TKN)
NOTES: Loadings are presented in Ibs/year. Preliminary loadings for TN only. Final loadings for TKN only.
Tables 4-2, 4-3, and 4-4 summarize the removal efficiency of pollutants for the overall system.
The data included within these tables reflects the relative comparison of the alternatives and a
theoretical simulation of the system with no Northshore and Brentwood Today Lakes. Median
values of pollutant removal efficiency have been referenced from the National Pollutant
Removal Database for Stonnivater Treatment Practices, 2"d Edition developed by the Center for
Watershed Protection and authored by Rebecca Winer. These values provide a baseline for
evaluation; however it must be understood that those median values represent a multitude of sites
under varied design conditions (new construction, retrofit, etc).
Water Quality Evaluation 13 February 2005
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Table 4-2
Overall TSS Removal Efficiency (%)
f' 1 GITR•7 • , C? ?1t ?l?FTiit•"f1i?i ? ;_'il'?15 ?{..L ]! '? jI I:Ud•]hI JUIllut 11 t?[•a ?;c t
Average 71 81 76` 10
1-Inch Design 62 73 67 9
NOTE; Removal efficiency measured in %.
TSS removal efficiencies ranged from 71 to 81 percent for the average year and 62 to 73 percent
for the 1-inch design storm. Median baseline levels of TSS removal for regional wet detention
ponds and stormwater wetlands are 70 and 80 percent, respectively (Winer, 2000). The Dam
Safety alternative, which contains only wet detention ponds as the main design element, is inline
with this median baseline level. The other alternatives, which include sediment pools and
wetlands, provide only minor increases (=5 percent) on this efficiency and are also in line with
the median baseline level (80 percent). The Recommended and Water Quality alternatives show
improvement in the removal efficiency of the middle two particle classes (P30, P50) as shown in
Figure 4-2. The removal of these particles is directly attributable to the filtering capacity of
wetlands. Dissolved particles (PO) are not significantly removed in any alternative.
Figure 4-2
Removal Efficiency (oIo) for Discrete Particles
100
90 --- - - --- - --- -- --
80 ----- -- -------
a 70 _.- - '-------- - - - - --- - - .-
c 60
.U
50
40 _._. ---- ------------ - - --. - - -.
0 30 - --- --- - -- -- --- -
a) 20 - - -- - -- ---- - -- ------- ---- ---
O
PO P10 P30 P50 P80
Particle Distribution
-s Dam Safety - s Recommended < - Water Quality
The preliminary assessment of TM #2 expressed removal efficiency of 80 percent for the overall
system in its current state. The efficiencies selected for Northshore and Brentwood Today Lakes
that culminated in that overall efficiency were likely over estimated; also, that assessment does
Water Quality Evaluation 14 February 2005
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not consider the conservative modeling of the unnamed lake upstream of Northshore Lake,
which reduced overall efficiency in this analysis. Removal efficiencies for the wet and dry year
were within two percent of the efficiency expressed for the average year. The No Lakes scenario
provides minor TSS removal (z10 percent), which is solely attributable to the efficiency of the
unnamed lake.
Table 4-3 displays overall TP removal efficiencies for the alternatives and the No Lakes
scenario. TP removal efficiencies ranged from 38 to 50 percent for the average year and 28 to 40
percent for the 1-inch design storm. Median baseline levels of TP removal for regional wet
detention ponds and stormwater wetlands are 48 and 43 percent, respectively (Winer, 2000). The
Dam Safety alternative, which contains only wet detention ponds as the main design element,
performs below the median level. The other alternatives, which include sediment pools and
wetlands, provide only minor increases (z6 percent) on this efficiency, as expected and are also
in line with the median baseline level (48 percent). The values in Table 4-3 only report TP
removed by settling. It would be expected that as TP breaks down into a non-particulate, bio-
available form (orthophosphorus), nutrient uptake would occur. The nutrient uptake would
improve upon the removal efficiencies displayed in this table for alternatives that include a
wetland. It is difficult to pinpoint the expected removal efficiency attributed to nutrient uptake
as water chemistry and vegetation selection would be major factors in the performance of the
wetland. It could also be expected that during winter months or poor wetland maintenance, that
the wetland would decrease removal efficiency or even be a source of TP.
Table 4-3
Ovefall TP Removal Efficiency (%)
.g ?.
Average 38 50 44 4
1- Inch Design 28 40 33 3
NOTE: Removal efficiency measured in °o.
The preliminary assessment of TM #2 expressed removal efficiency of 56 percent for the overall
system in its current state. The efficiencies selected for Northshore and Brentwood Today Lakes
that culminated in that overall efficiency were likely over estimated; also, that assessment does
not consider the conservative modeling of the unnamed lake upstream of Northshore Lake.
Removal efficiencies for the wet and dry year were within 1 percent of the efficiency expressed
for the average year. The No Lakes scenario provides minor TP removal (--4 percent), which is
primarily attributable to the efficiency of the unnamed lake.
Dater Quality Evaluation 15 February 2005
of Conceptual Plans

Table 4-4 displays overall TKN removal efficiencies for the alternatives and the No Lakes
scenario. TKN removal efficiencies ranged from 33 to 44 percent for the average year and 24 to
36 percent for the 1-inch design storm. Median baseline levels of TN removal for regional wet
detention ponds and stormwater wetlands are 37 and 35 percent, respectively (Winer, 2000).
TKN represents the primarily settleable component of TN. Therefore, it can be roughly assumed
that design elements involving only removal by settling would equate TN and TKN removal
efficiency. The Dam Safety alternative, which contains only wet detention ponds and, therefore,
emphasizes particulate settlement as its primary removal mechanism, performs in line with the
median baseline level for TN. The other alternatives, which include sediment pools and
wetlands, provide only minor increases (z6 percent) on this efficiency. The values in Table 4-4
only report TKN removed by settling. It would be expected that as TKN breaks down and
transforms into non-particulate, bio-available forms, such as ammonium (NHL+) and nitrite-
nitrate (NOZ -NO3-) nutrient uptake would occur. The nutrient uptake would improve upon the
removal efficiencies displayed in this Table for alternatives that include a wetland. The median
level of NO, removal in a stormwater wetland versus as wet pond is triple (68 versus 23 percent).
It is difficult to pinpoint the expected removal efficiency attributed to nutrient uptake as water
chemistry and vegetation selection would be major factors in the performance of the wetland. It
could also be expected that during winter months or poor wetland maintenance, that the wetland
would decrease removal efficiency or even be a source of TN/TKN.
Table 4-4
Overall TICN Removal Efficiency (°Io)
92-M J
Average 33 44 38 4
1- Inch Design 24 36 29 2
NOTE: Removal efficiency measured in %.
The preliminary assessment of TM #2 expressed removal efficiency for TN of 31 percent for the
overall system in its current state. That estimation was fairly accurate as the TKN removal for
the Dam Safety alternative is within range. Removal efficiencies for the wet and dry year were
within 1 percent of the efficiency expressed for the average year. The No Lakes scenario
provides minor TKN removal (=4 percent), which is primarily attributable to the efficiency of
the unnamed lake.
Tables 4-5, 4-6, and 4-7 summarize the cumulative load entering the stream downstream of
Brentwood Today Lake. Once again, the strength of P8-UCM is not in absolute prediction of
loadings and concentrations; therefore, the alternatives were executed and reported for a
Water Quality Evaluation 16 February 2005
of Conceptual Plans
01
statistically dry, average, and wet year off rainfall volume. These results demonstrate the range
of loading that could occur under different hydrologic conditions and during a typical design
storm (1-inch SCS Type lI distribution). These values may provide reference in determining
downstream impacts.
Table 4-5
TSS Loading (Ibs) discharged out of Breuhvood Today Lake
Hydrologi e I t M.
Dry 126,500 86,100 106,500 379,500
Average 137,000 91,200 113,700 421,300
Wet 168,500 113,400 141,100 503,600
1- Inch Design 4,300 3,000 3,700 10,300
NOTE: Loadings measured in Ibs.
Table 4-G
r) discharged out c
680
750
900
20
rf Breutfvood Today Lake
760 1,390
840 1,440
1,020 1,700
20 40
NOTE: Loadings measured in Ibs.
TP Loading (lb,
..ra TM, M
Dry 840
Average 930
Wet 1,120
1- Inch Design 20
Table 4-7
TKN Loading (lbs) discharged out of Brentwood Today Lake
Dry 4,060 3,390 3,750 5,800
Average 4,530 3,780 4,170 6,500
Wet 5,410 4,530 5,000 7,700
1- Inch Design 130 110 120 160
NOTE: Loadings measured in Ibs.
Water Quality Evaluation 17 Febnsary 2005
of Conceptual Plans

SECTION 5.0 - MODEL EVALUATION
5.1 Continuity Errors
P8-UCM performs continuous water-balance and mass-balance checks for single devices and the
entire network. Differences in these checks are identified as continuity errors, which can be
highlighted to the user through the setting of a maximum continuity difference. These continuity
errors are typical of devices with large, rapid fluctuations in volume (e.g., swales/buffers, smaller
detention ponds) (Walker, 1990). Continuity errors can be controlled through a reduced time
step. It was necessary in this modeling effort to run all scenarios with a time step = 8, in order to
reduce continuity errors within the smaller detention ponds representing sediment pools. A
comparison analysis of a particular model run at a time step = 1 and = 8 demonstrated minor
differences in removal efficiency results (less than 1.5 percent). Concentrations and loads
demonstrated slightly higher differences (2 to 6 percent) with the higher end of these differences
occurring in the TSS concentrations.
5.2 Sensitivity Analysis
As previously discussed, P8-UCM and other water quality models exhibit a high level of
variability. Many of the parameters used within this model are based upon estimation and
generalized calibrations; therefore, it is beneficial to understand which of these parameters may
significantly impact the results when not properly quantified. P8-UCM includes a utility that
automates sensitivity analysis for a desired scenario. The sensitivity analysis utility groups input
parameters into four categories: watershed, device, storm, and particle. The parameters for the
first three of these groups are typically user defined and the final group, particle, include default
parameters.
A sensitivity analysis was performed for the water quality scenario since it included the full
range of devices and their parameters. This analysis was run for the average precipitation year
and the variables were increased 25 percent individually. There were two primary observations
from the results of this analysis. Removal efficiencies were less affected than outflow
concentrations by the change in parameters. This reinforces the value of the model as a relative
predictor among scenarios. The second observation showed that the most variable parameters
were in the particle group; a default group of data based on field and laboratory data collected
from a multitude of sites for the NURP program. The parameters demonstrating the highest
variability were the accumulation rate, accumulation decay rate, and wash-off exponent. Their
sensitivity measured as percent change for removal efficiencies and concentrations ranged from
near 0 to 21.6 percent and 3.6 to 24.8 percent, respectively. The high variability in wash-off
hater Quality Evaluation 18 February 2005
of Conceptual Plans

exponent is due to the exponential response it yields in comparison to linear coefficients
(Walker, 1990). Watershed areas and storm volumes also produced a significant sensitivity as
expected, however they are parameters that can be calculated with confidence.
SECTION 6.0 - CONCLUSION AND DISCUSSION
The purpose of this TM and water quality evaluation was to develop sound input for the relative
evaluation of several proposed alternatives. These alternatives were developed to reestablish or
improve lost functions of Northshore and Brentwood Today Lakes. It was determined that a
modeling effort would provide an objective means of evaluation of these alternatives with
respect to water quality. P8-UCM, an urban runoff model, was selected as a tool that could
objectively evaluate a range of scenarios with limited data. The P8-UCM modeling effort
allowed for the creation of baseline input data, definition of several design elements or BMPs,
and simulation of physical pollutant removal processes. The modeling effort yielded several
sets of data that could be conservatively interpreted into water quality benefits of the varying
alternatives. The water quality benefits are an essential determining factor, but not the only
factor, for the selection and implementation of an alternative for rehabilitation of Northshore and
Brentwood Today Lakes.
Based on this evaluation of pollutant loadings and BMP removal efficiency with results from the
Preliminary Assessment and nationally/regionally expected performance levels the following
conclusions are made:
¦ The use of NURP calibrated particle distribution data allows for the discrete mass
accumulation and removal of particles and their bound pollutants. Regional EMC values
would produce more representative loading but do not provide for accurate removal
efficiency development. Removal efficiency development was a goal of this effort.
¦ Overall pollutant removal efficiencies for TSS did not improve significantly. As expected the
existing lake systems function well with regards to settling out of TSS. However, the
existing system does not provide an accessible, cost effective means of permanently
removing sediment that can be achieved with a sediment pool.
¦ Overall pollutant removal efficiencies for the middle ranged particles (P30 and P50) are
higher in alternatives that include a wetland. There is no significant change in removal for
large particles (P80) and dissolved particles (PO) in any alternative.
Water Quality Evaluation 19 February 2005
of Conceptual Plans
I
¦ Pollutant removal efficiencies for TP are expected to be higher in the Water Quality and
Recommended alternative than reported. P8-UCM does not account for orthophosphorus
uptake in wetlands, which could significantly increase TP removal.
¦ Pollutant removal efficiencies for TN would be expected to be lower than reported TKN
removal values as TKN is a single component of TN. However, these efficiencies should
bounce back for the Water Quality and Recommended alternative. P8-UCM does not
account for ammonium or nitrite/nitrate uptake in wetlands, which could significantly
increase overall TN removal.
¦ The TN removal efficiency for the Water Quality and Recommended alternative should
fulfill a TN reduction of at least 30 percent per Neuse River Nutrient Management Strategy,
although that requirement is for singular, new development.
¦ Furthermore, pollutant removal efficiencies may be negatively impacted without proper
maintenance and harvesting of BMPs that present the opportunity to permanently remove
pollutants from the Lakes system.
¦ The addition of wetlands and sediment pools would provide for more laminar flow regions
near the headwaters of the lake and increase hydraulic residence time. These changes could
increase the potential for fecal coliform die off and lessen downstream impact through
ultraviolet radiation and longer travel time.
This water quality evaluation provides evidence that the Recommended and Water Quality
alternative demonstrate improvement in pollutant removal efficiency over the Dam Safety
alternative, which provides better function of flood control over existing lake conditions by
reconfiguration and construction of new spillways. The relative water quality results of the
alternatives and other benefits of the inclusive design elements should be taken from this TM
and used in the global evaluation of alternatives to be discussed further in an Alternative
Design Summary and Final Report. Their level of value must be weighed against results of
other analyses to determine the best alternative for Northshore and Brentwood Today Lakes.

l
Water Quality Evaluation 20 February 2005
of Conceptual Plans
•

SECTION 7.0 - RE, FERENCES
Haith, D.A. and L.L. Shoemaker, 1987. "Generalized Watershed Loading Functions for Stream
Flow Nutrients", Water Resources Bulletin, American Water Resources Association, Vol. 23 No.
3.
Hamon, W.R., 1961. "Estimating Potential Evapotranspiration", Proceedings of the American
Society of Civil Engineers , Journal of Hydraulics Division, Vol. 87, No. HY3.
US Environmental Protection Agency, 1992. Compendium of Watershed-Scale Models for
TMDL Development, Washington D.C., 841R94002.
US Environmental Protection Agency, 1999. Protocol for Developing Nutrient TMDLs,
Washington D.C., 841B99007.
Wright-McLaughlin Engineers, 1969. Urban Storm Drainage Criteria Manual, Denver, Colorado.
Soil Conservation Service, 1986. Urban Hydrology for Small Watersheds, Technical Release
No. 55, US Department of Agriculture, Washington D.C.
Walker, William W, Jr. Ph.D., 1990. P8 Urban Catchment Model: Program Documentation,
Concord, Massachusetts.
Winer, Rebecca, 2000. National Pollutant Removal Performance Results for Stormwater
Treatment Devices, 2°a Edition. Center for Watershed Protection, Elliot City, Maryland.
Water Quality Evaluation 21 February 2005
of Conceptual Plans
00567205
200` 206 ?IrcG;?7???ITc
.JUN 3 0 2005
DE:NR - WA)'FR UIJALITY
WETLANDS AND S i0RNS4'J1 TE R BRANCH
NC DEPT OF ENVIRONMENT & NATURAL RESOURC
NC DIVISION OF WATER QUALITY
401 WETLANDS UNIT
1650 MAIL SERVICE CENTER
RALEIGH NC 27699-1650
NUMBER DATE ..' MOUNT t DISCOUNT• TAX„ ADD: cHRO, , NET'AMOUNT
LAKEREHABPROJCT 06/16/05 475.00 .00 .00 .00 475.00