20081477 Ver 1_Modifications_20081030

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community infrastructure consultants
October 29, 2008
Ms. Crystal Amschler
US Army Corps of Engineers
Raleigh Regulatory Field Office
331 Heritage Trade Drive, Suite 105
Wake Forest, NC 27587
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COPY
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OCT 3 0 2008
DENR • WATER QUALI I'
WETLANDS AND STQRMWATER BRANCH
RE: Response to comments on PCNs for Culvert Improvements at Kaplan Drive (AID No. 2008-
02785) and Swift Drive (AID No. 2008-02783)
Dear Ms. Amschler:
Attached to this letter are updated PCN forms, narratives, and design plans for the proposed Kaplan
Drive and Swift Drive culvert improvements. The modifications are based on your emailed comments
on October 20, 2008 and our subsequent phone conversations. As requested the PCNs have been
changed to NWP 14 - Linear Transportation Projects. Other requested changes have been made as
follows:
Kaplan Drive - The culvert design has been modified from a weir type baffle to one box remaining
open to convey base flow and baffling the second box one foot to convey storm flow (per Regional
Condition 4.2). The open box is in-line with relocated channel. The PCN form and narrative have
been edited to more accurately describe the impacts and the improvements to hydraulic efficiency.
Other minor edits have been made to the PCN form and narrative to reflect comments from NCDWQ
401 Unit.
Swift Drive - The culvert design has been modified from a weir type baffle to one box remaining open
to convey base flow and baffling the second box one foot to convey storm flow (per Regional
Condition 4.2). The open box is in-line with the existing channel. Other minor edits have been made
to the PCN form and narrative to reflect comments from NCDWQ 401 Unit.
The 401 Certifications have already been issued for the proposed projects. Please contact me if you
have any questions regarding this PCN submittal ([e-mail]). Thank you for your
prompt attention to these important flood control projects.
Sincerely,
W.K. Dickson & Co., Inc.
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Daniel Ingram
Project Scientist
T1 car7
cc: Ian McMillan, NCDWQ t opr5
Craig Deal, Project Manager
Tom Murray, PE, Project Manager
File: 60319.00. RA
20 C..or por'We C ('ilea Dr i% e
Raleigh, NC' 2-607
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Office Use Only: Form Version March 08
USACE Action ID No. DWQ No. o0, - I Lk 1 1 V2,
(If any particular item is not applicable to this project, please enter "Not Applicable" or "N/A".)
1. Processing (+l()UR- EZ)
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1. Check all of the approval(s) requested for this project:
® Section 404 Permit ? Riparian or Watershed Buffer Rules
? Section 10 Permit ? Isolated Wetland Permit from DWQ
? 401 Water Quality Certification ? Express 401 Water Quality Certification
2. Nationwide, Regional or General Permit Number(s) Requested:
NWP 14
3. If this notification is solely a courtesy copy because written approval for the 401 Certification
is not required, check here: ?
4. If payment into the North Carolina Ecosystem Enhancement Program (NCEEP) is proposed
for mitigation of impacts, attach the acceptance letter from NCEEP, complete section VIII,
and check here: ?
5. If your project is located in any of North Carolina's twenty coastal counties (listed on page
4), and the project is within a North Carolina Division of Coastal Management Area of
Environmental Concern (see the top of page 2 for further details), check here: ?
II. Applicant Information D
Owner/Applicant Information
pOfi 3 0 2008
Name: City of Raleigh 1*% _WATER©U . A???BRASDH
Mailing Address: Public Works Department tiEnANDSAMD da'ta`
222 West Hargett Street
Raleigh, NC 27602-0590
Attn: Carl Dawson, P.E.
Telephone Number: [phone] Fax Number: [phone]
E-mail Address: [e-mail]
2. Agent/Consultant Information (A signed and dated copy of the Agent Authorization letter
must be attached if the Agent has signatory authority for the owner/applicant.)
Name: Daniel Ingram
Company Affiliation: WK Dickson
Mailing Address: 720 Corporate Center Drive
Raleigh, NC 27607
Telephone Number: 919-782-0495 Fax Number: 919-782-9672
E-mail Address: [e-mail]
Page I of 8
III. Project Information
Attach a vicinity map clearly showing the location of the property with respect to local
landmarks such as towns, rivers, and roads. Also provide a detailed site plan showing property
boundaries and development plans in relation to surrounding properties. Both the vicinity map
and site plan must include a scale and north arrow. The specific footprints of all buildings,
impervious surfaces, or other facilities must be included. If possible, the maps and plans should
include the appropriate USGS Topographic Quad Map and NRCS Soil Survey with the property
boundaries outlined. Plan drawings, or other maps may be included at the applicant's discretion,
so long as the property is clearly defined. For administrative and distribution purposes, the
USACE requires information to be submitted on sheets no larger than 11 by 17-inch format;
however, DWQ may accept paperwork of any size. DWQ prefers full-size construction
drawings rather than a sequential sheet version of the full-size plans. If full-size plans are
reduced to a small scale such that the final version is illegible, the applicant will be informed that
the project has been placed on hold until decipherable maps are provided.
1. Name of project: Kaplan Drive Culvert Improvement
2. T.I.P. Project Number or State Project Number (NCDOT Only):
3. Property Identification Number (Tax PIN): 783574025 (City of Raleigh)
4. Location
County: Wake Nearest Town: Raleigh
Subdivision name (include phase/lot number):
Directions to site (include road numbers/names, landmarks, etc.): Take the Gorman Street exit
from 1-40 and proceed north at the light at the end of the ramp. Take a left onto Avent Ferry Road and
go approximately 1.5 miles west. Take a right onto Kaplan Drive and go approximately 0.5 miles to the
culvert immediately after Ravel Street.
5. Site coordinates (Lat/Long or decimal degrees): 35.775°N -78.711°W
(Note - If project is linear, such as a road or utility line, attach a sheet that separately lists the coordinates for
each crossing of a distinct waterbody.)
6. Property size (acres): 0.25 (area of disturbance)
7. Name of nearest receiving body of water: Simmons Branch
8. River Basin: Neuse River Basin (03020201)
(Note - this must be one of North Carolina's seventeen designated major river basins. The
River Basin map is available at http://h2o.enr.state.nc.us/admin/mgps/.)
9. Describe the existing conditions on the site and general land use in the vicinity of the project
at the time of this application: The attached project narrative describes existing conditions.
10. Describe the overall project in detail, including the type of equipment to be used: The
attached project narrative describes the project in detail.
Page 2 of 8
11. Explain the purpose of the proposed work: the attached project narrative describes the
purpose of the proposed work in detail.
IV. Prior Project History
If jurisdictional determinations and/or permits have been requested and/or obtained for this
project (including all prior phases of the same subdivision) in the past, please explain. Include
the USACE Action ID Number, DWQ Project Number, application date, and date permits and
certifications were issued or withdrawn. Provide photocopies of previously issued permits,
certifications or other useful information. Describe previously approved wetland, stream and
buffer impacts, along with associated mitigation (where applicable). If this is a NCDOT project,
list and describe permits issued for prior segments of the same T.I.P. project, along with
construction schedules. No permits exist at this time for this project.
V. Future Project Plans
Are any future permit requests anticipated for this project? If so, describe the anticipated work,
and provide justification for the exclusion of this work from the current application.
None at this time.
VI. Proposed Impacts to Waters of the United States/Waters of the State
It is the applicant's (or agent's) responsibility to determine, delineate and map all impacts to
wetlands, open water, and stream channels associated with the project. Each impact must be
listed separately in the tables below (e.g., culvert installation should be listed separately from
riprap dissipater pads). Be sure to indicate if an impact is temporary. All proposed impacts,
permanent and temporary, must be listed, and must be labeled and clearly identifiable on an
accompanying site plan. All wetlands and waters, and all streams (intermittent and perennial)
should be shown on a delineation map, whether or not impacts are proposed to these systems.
Wetland and stream evaluation and delineation forms should be included as appropriate.
Photographs may be included at the applicant's discretion. If this proposed impact is strictly for
wetland or stream mitigation, list and describe the impact in Section VIII below. If additional
space is needed for listing or description, please attach a separate sheet.
1. Provide a written description of the proposed impacts: The attached project narrative
describes the proposed impacts in detail.
2. Individually list wetland impacts. Types of impacts include, but are not limited to
mechanized clearing, grading, fill, excavation, flooding, ditching/drainage, etc. For dams,
separately list impacts due to both structure and floodiniz.
Wetland Impact - Type of Wetland Located within Distance to Area of
Site Number Type of Impact (e.g., forested, marsh, 100-year Nearest Impact
(indicate on map) herbaceous, bog, etc.) Floodplain Stream (acres)
es/no) (linear feet)
Total Wetland Impact (acres) NA
Page 3 of 8
3. List the total acreage (estimated) of all existing wetlands on the property: NA
4. Individually list all intermittent and perennial stream impacts. Be sure to identify temporary
impacts. Stream impacts include, but are not limited to placement of fill or culverts, dam
construction, flooding, relocation, stabilization activities (e.g., cement walls, rip-rap, crib
walls, gabions, etc.), excavation, ditching/straightening, etc. If stream relocation is proposed,
plans and profiles showing the linear footprint for both the original and relocated streams
must be included. To calculate acreage, multiply length X width, then divide by 43,560.
Stream Impact Stream Perennial or Average Impact Area of
Number Name Type of Impact Intermittent? Stream Width Length Impact
(indicate on ma) Before Impact (linear feet) (acres)
Simmons Upstream channel
1 Branch relocation and culvert Perennial 10 72 0.02
upgrade
Simmons Downstream channel
2 Branch relocation and culvert Perennial 10 54 0.01
upgrade
Total Stream Impact (by length and acreage) 126 0.03
5. Individually list all open water impacts (including lakes, ponds, estuaries, sounds, Atlantic
Ocean and any other water of the U.S.). Open water impacts include, but are not limited to
fill, excavation, dredging, flooding, drainage, bulkheads, etc.
Open Water Impact Name of Waterbody Type of Waterbody Area of
Site Number (if applicable) Type of Impact (lake, pond, estuary, sound, bay, Impact
(indicate on ma) ocean, etc.) (acres)
Total Open Water Impact (acres) NA
6. List the cumulative impact to all Waters of the U. S. resulting from the project:
Stream Impact (acres): 0.03
Wetland Impact (acres): 0.00
Open Water Impact (acres): 0.00
Total Impact to Waters of the U.S. (acres) 0.03
Total Stream Impact (linear feet): 126
7. Isolated Waters
Do any isolated waters exist on the property? ? Yes ® No
Describe all impacts to isolated waters, and include the type of water (wetland or stream) and
the size of the proposed impact (acres or linear feet). Please note that this section only
applies to waters that have specifically been determined to be isolated by the USACE.
Page 4 of 8
8. Pond Creation
If construction of a pond is proposed, associated wetland and stream impacts should be
included above in the wetland and stream impact sections. Also, the proposed pond should
be described here and illustrated on any maps included with this application.
Pond to be created in (check all that apply): ? uplands ? stream ? wetlands
Describe the method of construction (e.g., dam/embankment, excavation, installation of
draw-down valve or spillway, etc.):
Proposed use or purpose of pond (e.g., livestock watering, irrigation, aesthetic, trout pond,
local stormwater requirement, etc.):
Current land use in the vicinity of the pond:
Size of watershed draining to pond: Expected pond surface area:
VII. Impact Justification (Avoidance and Minimization)
Specifically describe measures taken to avoid the proposed impacts. It may be useful to provide
information related to site constraints such as topography, building ordinances, accessibility, and
financial viability of the project. The applicant may attach drawings of alternative, lower-impact
site layouts, and explain why these design options were not feasible. Also discuss how impacts
were minimized once the desired site plan was developed. If applicable, discuss construction
techniques to be followed during construction to reduce impacts. The attached project narrative
describes impact justification and avoidance.
VIII. Mitigation
DWQ - In accordance with 15A NCAC 2H .0500, mitigation may be required by the NC
Division of Water Quality for projects involving greater than or equal to one acre of impacts to
freshwater wetlands or greater than or equal to 150 linear feet of total impacts to perennial
streams.
USACE - In accordance with the Final Notice of Issuance and Modification of Nationwide
Permits, published in the Federal Register on January 15, 2002, mitigation will be required when
necessary to ensure that adverse effects to the aquatic environment are minimal. Factors
including size and type of proposed impact and function and relative value of the impacted
aquatic resource will be considered in determining acceptability of appropriate and practicable
mitigation as proposed. Examples of mitigation that may be appropriate and practicable include,
but are not limited to: reducing the size of the project; establishing and maintaining wetland
and/or upland vegetated buffers to protect open waters such as streams; and replacing losses of
aquatic resource functions and values by creating, restoring, enhancing, or preserving similar
functions and values, preferable in the same watershed.
If mitigation is required for this project, a copy of the mitigation plan must be attached in order
for USACE, or DWQ to consider the application complete for processing. Any application
lacking a required mitigation plan or NCEEP concurrence shall be placed on hold as incomplete.
An applicant may also choose to review the current guidelines for stream restoration in DWQ's
Draft Technical Guide for Stream Work in North Carolina, available at
hiip://h2o.enr.state.nc.us/newetlands/stnnizide.html.
Page 5 of 8
1. Provide a brief description of the proposed mitigation plan. The description should provide
as much information as possible, including, but not limited to: site location (attach directions
and/or map, if offsite), affected stream and river basin, type and amount (acreage/linear feet)
of mitigation proposed (restoration, enhancement, creation, or preservation), a plan view,
preservation mechanism (e.g., deed restrictions, conservation easement, etc.), and a
description of the current site conditions and proposed method of construction. Please attach
a separate sheet if more space is needed.
The attached project narrative describes mitigative measures in detail.
2. Mitigation may also be made by payment into the North Carolina Ecosystem Enhancement
Program (NCEEP). Please note it is the applicant's responsibility to contact the NCEEP at
[phone] to determine availability, and written approval from the NCEEP indicating
that they are will to accept payment for the mitigation must be attached to this form. For
additional information regarding the application process for the NCEEP, check the NCEEP
website at http://h2o.enr.state.nc.us/wvM/index.htm. If use of the NCEEP is proposed, please
check the appropriate box on page three and provide the following information:
Amount of stream mitigation requested (linear feet):
Amount of buffer mitigation requested (square feet):
Amount of Riparian wetland mitigation requested (acres):
Amount of Non-riparian wetland mitigation requested (acres):
Amount of Coastal wetland mitigation requested (acres):
IX. Environmental Documentation (required by DWQ)
1. Does the project involve an expenditure of public (federal/state/local) funds or the use of
public (federal/state) land? Yes ® No ?
2. If yes, does the project require preparation of an environmental document pursuant to the
requirements of the National or North Carolina Environmental Policy Act (NEPA/SEPA)?
Note: If you are not sure whether a NEPA/SEPA document is required, call the SEPA
coordinator at [phone] to review current thresholds for environmental documentation.
Yes ? No
3. If yes, has the document review been finalized by the State Clearinghouse? If so, please
attach a copy of the NEPA or SEPA final approval letter. Yes ? No ?
X. Proposed Impacts on Riparian and Watershed Buffers (required by DWQ)
It is the applicant's (or agent's) responsibility to determine, delineate and map all impacts to
required state and local buffers associated with the project. The applicant must also provide
justification for these impacts in Section VII above. All proposed impacts must be listed herein,
and must be clearly identifiable on the accompanying site plan. All buffers must be shown on a
map, whether or not impacts are proposed to the buffers. Correspondence from the DWQ
Page 6 of 8
Regional Office may be included as appropriate. Photographs may also be included at the
applicant's discretion.
1. Will the project impact protected riparian buffers identified within 15A NCAC 2B .0233
(Meuse), 15A NCAC 2B .0259 (Tar-Pamlico), 15A NCAC 02B .0243 (Catawba) 15A NCAC
2B .0250 (Randleman Rules and Water Supply Buffer Requirements), or other (please
identify )? Yes ® No ?
2. If "yes", identify the square feet and acreage of impact to each zone of the riparian buffers.
If buffer mitigation is required calculate the required amount of mitigation by applying the
buffer multipliers.
Zone* Impact
(square feet) Multiplier Required
Mitigation
1 5,797 3 (2 for Catawba)
2 362 1.5
Total 6,159
* Zone 1 extends out 30 feet perpendicular from the top of the near bank of channel; Zone 2 extends an
additional 20 feet from the edge of Zone 1.
3. If buffer mitigation is required, please discuss what type of mitigation is proposed (i.e.,
Donation of Property, Riparian Buffer Restoration / Enhancement, or Payment into the
Riparian Buffer Restoration Fund). Please attach all appropriate information as identified
within 15A NCAC 2B .0242 or .0244, or .0260. the attached project narrative describes
buffer mitigative measures in detail.
XI. Stormwater (required by DWQ)
Describe impervious acreage (existing and proposed) versus total acreage on the site. Discuss
stormwater controls proposed in order to protect surface waters and wetlands downstream from
the property. If percent impervious surface exceeds 20%, please provide calculations
demonstrating total proposed impervious level. The proposed project does not require stormwater
planning per DWQ guidance.
XII. Sewage Disposal (required by DWQ)
Clearly detail the ultimate treatment methods and disposition (non-discharge or discharge) of
wastewater generated from the proposed project, or available capacity of the subject facility.
NA
XIII. Violations (required by DWQ)
Is this site in violation of DWQ Wetland Rules (15A NCAC 2H .0500) or any Buffer Rules?
Yes= ? No
Page 7 of 8
Is this an after-the-fact permit application? Yes ? No
XIV. Cumulative Impacts (required by DWQ)
Will this project (based on past and reasonably anticipated future impacts) result in additional
development, which could impact nearby downstream water quality? Yes ? No Z
If yes, please submit a qualitative or quantitative cumulative impact analysis in accordance with
the most recent North Carolina Division of Water Quality policy posted on our website at
http://b2o.enr,state.nc.us/ncwetlands. If no, please provide a short narrative description: The
project is maintenance upgrades of an existing culvert to reduce flooding. The surrounding watershed is
almost entirely developed and the project should have no impact on future land use.
XV. Other Circumstances (Optional):
It is the applicant's responsibility to submit the application sufficiently in advance of desired
construction dates to allow processing time for these permits. However, an applicant may
choose to list constraints associated with construction or sequencing that may impose limits on
work schedules (e.g., draw-down schedules for lakes, dates associated with Endangered and
Threatened Species, accessibility problems, or other issues outside of the applicant's control).
None.
Applicant/Agent's Sig ture D??o (Agent's signature is valid onl f an authorizaion ?Ja
letter
# J c??
the applicant is provided.)
Updated 11/1/2005
Page 13 of 13
PRE-CONSTRUCTION NOTIFICATION
NATIONWIDE PERMIT 14
PROPOSED KAPLAN DRIVE CULVERT IMPROVEMENTS
SIMMONS BRANCH DRAINAGE BASIN
WAKE COUNTY, NORTH CAROLINA
PROJECT NARRATIVE
Introduction
The Kaplan Drive culvert upgrade is part of a watershed wide plan for Simmons Branch to
reduce roadway and structure flooding in a predominantly residential neighborhood in
West Raleigh. The Kaplan Drive roadway currently overtops during the 2-year 24-hour
storm event based on built out land use conditions. Residential flooding occurs at two
houses within the vicinity of the Kaplan Drive culvert crossing based on survey elevations
provide by the City of Raleigh. The proposed project is designed to convey the 10-year
24-hour storm based on future land use conditions. The proposed culvert upgrade will
substantially reduce roadway flooding in the project area and reduce residential flooding.
Site Location and Description
Simmons Branch drains approximately 1.2 mil from Western Boulevard to south of Avent
Ferry Road (Figure 1). The stream discharges to Walnut Creek just south of Lake Johnson.
While commercial areas in the vicinity of Western Boulevard have developed in recent
years, the majority of land use along Kaplan Drive is residential. Rain events in 2001
caused significant residential flooding in the watershed precipitating the "Simmons Branch
Drainage Study", completed in 2002. Recommended project locations from the 2002
study are intended to provide a 10-year level of service at major roadway crossings
assuming built out conditions in the watershed.
The existing culvert crossing at Kaplan Drive consists of 65 linear feet of twin 54"
reinforced concrete pipe. The headwalls on each side are block walls with 45 degree
wing walls. The culvert currently overtops during the 2-year 24-hour storm event. One
residence located downstream of the culvert experiences flooding during the 10-year 24-
hour storm event based on model results. Design constraints for the Kaplan Drive culvert
crossing include large trees upstream and downstream of the culvert along the channel
banks, a sanitary sewer conflict, and a pedestrian bridge located upstream of Kaplan Drive.
The latitude and longitude coordinates are 35.775N -78.711 W.
The topography on the property consists of moderately sloping terrain. Simmons Branch
flows from west to east through the middle of the project area. The project area generally
drains to the south, away from Kaplan Drive, eventually draining into Walnut Creek. The
site is located in the Neuse river basin (HUC 03020201).
Project Description and Purpose
The purpose of the proposed project is to increase channel and culvert efficiency and
capacity to reduce roadway flooding and flood risk to existing structures. Kaplan Drive is
Proposed Culvert Improvements in the Simmon's Branch Drainage Basin Page 2
neighborhood thoroughfare for West Raleigh and road closures due to flooding are a
public safety concern. Two homes are subject to flooding as well. The proposed project is
part of a watershed level initiative to reduce flooding. Bank stability improvements will
also decrease erosion and improve water quality and aquatic habitat.
Based on the analysis of the existing conditions hydraulic model for Kaplan Drive, a 10' x
6' box culvert will convey the 10-year storm event; however this resulted in high velocities
downstream of the culvert in excess of 15 feet per second during the 10-year event. These
high velocities would require significant downstream erosion protection most likely
including a stilling basin. A 14' x 6' box culvert is proposed to reduce velocities thereby
reducing the risk of erosion and scour. The 10-year velocity through the 14' x 6' culvert
would be approximately 6.5 feet per second. Erosion protection upstream and
downstream of the culvert will still be required, but would be manageable with standard
protection techniques such as matting, live stakes, and seeding. A configuration of twin 7'
x 7' boxes, buried one foot, is proposed. One box will placed in-line with the relocated
channel and left open to convey base flow. The second box will be baffled approximately
one foot to only convey storm flows.
To improve hydraulic efficiency, reduce bank erosion, and avoid a significant sanitary
sewer conflict, the existing stream channel will be re-located to the south approximately
35 feet. The relocated channel will eliminate a 90-degree bend immediately upstream of
the existing culvert and allow the channel to enter the culvert perpendicularly. Relocating
the Kaplan Drive culvert south of the existing alignment will avoid a conflict with an
existing 12" clay sanitary sewer line. The sanitary sewer is underneath the existing culvert
crossing. By realigning the existing channel and culvert south of the current location, the
new culvert will avoid a conflict with the sanitary sewer line. Conflict avoidance in this
instance will reduce the overall construction cost and avoid additional impacts to streams
and riparian buffers. A sanitary realignment to avoid conflict with the existing alignment
would require the removal of several large trees in the Neuse Buffer and would potentially
cause additional utility conflicts under Kaplan Drive.
Equipment to be used will include typical earthmoving equipment and construction
equipment.
Jurisdictional Waters/Wetlands of the U.S.
One perennial stream is located in the central portion of the project area (Simmons
Branch). This stream is a tributary to Walnut Creek. The channel is typically ten feet wide.
No wetlands are present in the project area. Simmons Branch is a disturbed urban stream
with steep/vertical banks and many areas of active bank erosion. The riparian buffer is
mostly maintained lawn, right-of-way, or disturbed forest (Figure 2). The stream bed is
gravel with riffle-pool habitat present. No fish or benthic organisms were observed in the
channel at the time of the site visit.
Proposed Impacts to Waters of the US/Waters of the State
Storm water design requirements were obtained from the City of Raleigh stormwater
design manual entitled "City of Raleigh Stormwater Management Design Manual" dated
January 2002 and City of Raleigh code Section 10-3053. Design standards include:
Proposed Culvert Improvements in the Simmon's Branch Drainage Basin Page 3
• Systems must pass the 10-year 24-hour storm
• Culverts for more than 25 acres must have at least 2 feet of freeboard for the
10-year 24-hour storm and 6 inch of freeboard for the 100-year 24-hour
storm
• Pipe slopes shall be no less than 0.5% and no greater than 12%
• Minimum cover outside R.O.W is 0.5 feet
• Side slopes for vegetated channels should be no more than 3 to 1
Since the proposed culvert improvements will be retrofit in a predominantly developed
area, some of the design standards may not be feasible or cost effective. At a minimum the
culvert improvements were designed to convey the 10-year 24-hour storm based on future
land use conditions.
The project will impact a total of 126 linear feet of channel resulting from channel
relocation and culvert upgrade (54 feet downstream and 72 feet upstream from the existing
Kaplan Drive culvert). The new Kaplan Drive culvert will be 5 feet longer than the existing
culvert (70 feet proposed, 65 feet existing).
The proposed relocated channel will be 94 feet long (54 feet downstream, 40 feet
upstream); resulting in a total net loss of 32 linear feet of stream channel. The relocated
channel will be constructed using natural channel design techniques and will incorporate
rock cross weirs, riffle grade controls, and natural plantings to provide bed and bank
stability. No riprap or other hardened structures will be utilized for bed or bank
protection.
Avoidance and Minimization
Due to stream location, access considerations, and project requirements, impacts to
streams are unavoidable. The proposed culvert is being relocated south of the existing
culvert to avoid a sanitary sewer conflict, protect several large trees downstream of the
culvert, and to provide a more efficient entrance to the culvert which will result in a more
stable channel bank. Avoiding the sanitary sewer conflict will reduce Neuse Buffer
impacts and reduce the overall limits of disturbance. Stabilizing the left bank upstream of
the culvert will protect the roadway embankment and reduce sediment loads to the stream.
The proposed culvert is 5 feet longer than the existing culvert (70 feet proposed, 65 feet
existing) minimizing impacts from the relocation of the existing culvert. Because of the
culvert placement, the stream will need to be relocated immediately upstream and
downstream of the culvert. The total stream impacts for the realignment are 126 feet with
a proposed length estimated at 94 linear feet after the stream has been relocated. The
cumulative channel loss is 32 LF. The existing channel will be plugged as it connects into
the proposed channel on the upstream and downstream ends. The culvert will be baffled
and will be buried a foot with a scour pool forming naturally at a riffle grade control
structure.
Proposed Culvert Improvements in the Simmon's Branch Drainage Basin Page 4
The roadway width and fill slopes have been minimized while still fulfilling geometry and
traffic considerations. Stream disturbance width will be minimized and all conditions of
NWP 14 will be complied with.
The final site plan is the most practicable configuration in that it allows a usable yield of
land area while carefully configuring and placing infrastructure, utility lines, and roads to
minimize stream impact. Relocating the culvert will reduce stress on the upstream
channel bank, avoid sanitary sewer relocations, and preserve several large-sized trees on
the downstream end.
All impacts to waters of the U.S. have been avoided and minimized to the maximum
extent practicable. The attached project narrative describes avoidance and minimization
in detail. All conditions of NWP 3 will be satisfied to further minimize impacts.
jurisdictional Impacts
The total area of jurisdictional waters of the U.S. to be impacted by the proposed culvert
upgrade project is 0.03 acres of stream fill.
The stream fill is generated stream relocation and culvert upgrades. The impact is required
due to geometry constraints for the culvert upgrade to satisfy the flood control project
purpose.
Best Management Practices
Prior to the beginning of any construction activities, the applicant will implement Best
Management Practices (BMP's) to minimize erosion and migration of sediments into
affected waterways (streams and wetlands) during the construction phase. A detailed
Erosion Control Plan will be developed and submitted for review and permitting by the
local jurisdiction. It will include appropriate erosion and siltation control devices placed
between the construction area and adjacent waterways. These devices may include the use
of mulches, sediment basins, silt fences, or other devices capable of preventing erosion
and migration of sediments. Monitoring of BMP's will take place in accordance with the
requirements of the North Carolina NPDES general permit for construction activity to
assure that the erosion and sediment control devices are installed properly and maintained
in a functioning condition.
Compensatory Mitigation
The proposed project impacts 126 linear feet of stream. No off site mitigation is proposed
for this project. On site mitigative measures include use of natural channel design
techniques on 94 linear feet of relocated portions of Simmons Branch, strict erosion
control measures, and adherence to construction BMPs. Natural channel design
components include rock cross weirs, riffle grade control structures, coir matting on stream
banks, black willow live stakes, and use of a native riparian seed mik for stabilization. No
riprap or other hardened structures are proposed for bed or bank stability. It is proposed
that the relocated channel is self mitigating for the proposed impacts and no off-site
mitigation is required as net impacts are 32 linear feet.
Proposed Culvert Improvements in the Simmon's Branch Drainage Basin Page 5
Riparian and Watershed Buffers
The culvert upgrade at Kaplan Drive does not result in an increase in impervious surfaces.
The proposed project is in an urban watershed and forested riparian buffers are not
present. The riparian buffer has an existing land use of maintained residential lawn and
maintained right-of-way. There are several large trees with maintained grass below them.
Impacts to the riparian buffer will be minimal with only the removal of some small trees
along the stream banks and in the vicinity of the culvert upgrade. The stream channel loss
due to relocation is necessary to avoid conflicts with an existing sanitary sewer line
beneath the existing culvert. If the culvert were replaced in its current location then
impacts to the riparian buffer would increase as a result of replacing the sanitary sewer in
the project area. The trees that are removed will be replaced with appropriate native tree
species and the buffer replanted with appropriate native shrub species and stabilized with
a riparian seed mix on stream banks and turf grasses in residential areas. No offsite buffer
mitigation is proposed.
Floodplain Encroachment
The proposed project will not encroach upon the 100-year floodplain and is not in a flood
hazard area.
Threatened and Endangered Species
Table 1 below lists threatened and endangered species in Wake County. No protected
species or suitable habitat was observed in the project area. The proposed project is not
likely to adversely affect any protected species.
Table 1. Threatened and endangered species in nrniPrt area
Common Name
I Scientific Name
Federal Status
Record Status
Vertebrates
Red-cockaded woodpecker Picoides borealis Endangered Historic
Invertebrates
Dwarf wedgemussel Alasmidonta heterodon Endangered Current
Vascular Plants
Michaux's sumac Rhus michauxii Endangered Current
Cultural and Historical Resources
A database search of National Register of Historic Properties indicated no listed historic
properties in the project vicinity. Additionally, a site visit determined that no existing
structures will be impacted by the proposed project.
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