20001137 Ver 2_401 Application_20080815

I

August 15, 2008
US Army Corps of Engineers
Raleigh Regulatory Field Office
3331 Heritage Trade Drive
Suite 105
Wake Forest, North Carolina 27587
And
North Carolina Department of Environment
and Natural Resources
Division of Water Quality
401 Wetlands Unit
1650 Mail Service Center
Raleigh, North Carolina 27699-1786
RE: Laurel Hills Dam Spillway Upgrade Project
To Whom It May Concern:
P? IT
Pf-?
The City of Raleigh would like to submit a revised Pre-Construction Notification
Application form per the North Carolina Division of Water Quality's request for a
previously approved Pre-Construction Notification (PCN) Application for the Laurel
Hills Dam Spillway Upgrade in the City of Raleigh, Wake County, North Carolina. The
City of Raleigh proposes to make improvements to the dam and spillway in order to meet
current Dam Safety design standards. Recently, a Section 404 Nationwide Permit #3 was
re-issued for this project and is dated May 8, 2008 and we are now requesting 401 Water
Quality Certification and Riparian Buffer Rule approvals.
The Laurel Hills Dam Spillway Upgrade Project has been modified from our previous
PCN approval (DWQ ID #001137) which has since expired. Modifications were made to
the plans and specifications to incorporate changes requested as a part of the Dam Safety
review and property owner plan requests. These changes are itemized below:
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Laurel Hills Dam Spillway Upgrade Project August 15, 2008
City of Raleigh PCN Application Page 2
o The City of Raleigh has asked our consultant MACTEC Engineering to include a
water control plan for the project. In the past, our construction contractor was
tasked with devising a plan for water control that would meet criteria established
by the City and conforming to State requirements. The City decided to
incorporate a water control plan as a part of these construction drawings. The
water control plan consists of a temporary cofferdam and temporary drain pipe.
o The downstream property owner enjoyed the small, tranquil flow that currently
exists in the downstream channel section. The property owner was concerned that
the size of the weir length of the new riser would prevent much base flow from
flowing through the existing 24-inch diameter culvert which currently has a small
"waterfall-like effect" near the right end of the dam, as the flow discharges along
the right abutment contact which is located in natural rock. The normal pool
elevation that was approved by your office on March 23, 2000, is at an elevation
of 91.82' and is controlled by the 24-inch diameter culvert near the right end of
the dam. That elevation has not changed with the revised drawings. The top of
the riser structure shown on the previously approved drawings were at the same
elevation as normal pool. In response to the property owner's concerns, we have
raised the riser by 3 inches (0.25') in order to accommodate his request and to
alleviate his concerns. The City has also shown on the plans a requirement to
install a 21-inch restrictor plate over the opening of the 24-inch diameter culvert
inlet such that only 3 inches of flow depth can discharge through the culvert. In
this way, the inlet invert of the 24-inch diameter culvert will continue to control
the normal pool (with a maximum depth of flow of 3 inches at the inlet), but the
new riser to be constructed will still accommodate the required design storm event
without overtopping of the dam.
o The plans have also been revised to include additional information on shoring that
would be required in order to construct the project. Our engineering consultant
has proposed the use of bentonite clay type geomembrane along the sheet piling
to be used for shoring during construction of the dam. A detail illustrating the
location of this geomembrane is shown on construction plan sheet U-2 and
referenced in the technical specifications in section 2.4. LF Principal Spillway
Materials, Seepage Seal. If you have any questions regarding the use of this
geomembrane, our engineering consultant, J. Allen Tice, PE, with MACTEC
Engineering would be able to provide you with additional information if
necessary. Please contact me and I will arrange a meeting or phone call with Mr.
Tice to address your questions.
o The technical specifications have been modified to reflect changes listed above.
Laurel Hills Dam Spillway Upgrade Project August 15, 2008
City of Raleigh PCN Application Page 3
Please find enclosed copies of the Dam Safety permit for Approval to Repair and our
U.S. Army Corps of Engineers Nationwide Permit Number 3, and NC Erosion and
Sediment Control approval for the Laurel Hills Dam for your files. This project is a part
of the City of Raleigh's Bond Program and will have funds available for construction of
this project September 2008.
The City of Raleigh will submit five (5) copies of this application package to the Division
of Water Quality for processing of our 401 permit and Riparian Buffer Rules request and
one (1) copy of this application package to the US Army Corps Regulatory Field Office
to update their files since a permit was already re-issued for this project.
Please review the attached permit package, construction plans, and review fee in the
amount of $570.00 (check number 00667950). Should you require additional
information, please do not hesitate contacting me so that this additional information can
be sent to you as quick as possible. I can be reached at veronica.highgci.ralei h.nc.us or
by phone directly at [phone]. Thank you in advance for your review of this
permit request.
Sincerely,
?l
Veronica L. High, E.I.
Stormwater Project Engineer 11
City of Raleigh
Public Works Department, Stormwater Management Division
Cc: file
< V,"I 1 fMichael F. Fa;lcv. Governor
Q? R yQG William (. Ross h . Secretary
QU4 North Carolina Department of Environment and Natual Resources
Coleen H. Sullins. Director
Dirisionof ?katerQualm,
June 16, 2008
DWQ Project # 00-1137
Wake County
CERTIFIED MAIL: RETURN RECEIPT REQUESTED
City of Raleigh
Attn: Veronica High
P.O. Box 590
Raleigh, North Carolina 27602` Jtag
r?t' ?
Subject Property: City of Raleigh - Laurel Hills Dam
Renewal of Issued 401 Permit ?08
PERMITTING FEE MISSING VJ
Dear Ms. High:
On June 12, 2008 the Division of Water Quality (DWQ) received your letter dated June 10, 2004 for the
above referenced project. The DWQ has determined that your application was incomplete and/or
provided inaccurate information as discussed below. The project has been placed on hold as incomplete
until we receive the additional information and/or fee. Please provide the following so that we may
continue to review your project.
Additional Information Requested:
® A request for renewal/modification of an issued permit requires re-submission of five (5)
application sets and appropriate fee.
The fee for applications is $240 for projects impacting less than an acre of wetland and less
than 150 linear feet of streams whether intermittent or perennial). For projects impacting one
or more acres of wetland or 150 or more feet of streams (whether intermittent or perennial),
the fee is $570_
Please contact the DWQ within three weeks of the date of this letter to verify that you have received this
letter and that you remain interested in continuing to pursue permitting of your project and will be
providing the DWQ the requested information at a later date. Please contact this office in writing. If we
do not hear from you within three weeks, we will assume that you no longer want to pursue this project
and we will consider the project as returned.
This letter only addresses the application review and does not authorize any impacts to wetlands, waters
or protected buffers. Please be aware that any impacts requested within your application are not
authorized (at this time) by the DWQ. Please call Mr. Ian McMillan or me at 919-733-1786 if you have
any questions regarding or would like to set up a meeting to discuss this matter.
101 Oversight/Express Review Permittin_ knit
I6?0 Mail Service Center, Raleigh, North Carolina -17699-1650
'311 Crahnee Boulevard. Suite -1i0. Raleteh. North ( amltna 27604
Phonc 919-733-1796 / FAX 90-1-:3-681 - Internet o c
On,
NorihCarohua
, Yalm--ally
An Lqual Opportunity/Aftirmauye Action I mplwei - ?0 S, Recycledi I11"4, Foss ( nnAUmer Paper

CBKh-n j
SHi erelY
Cyndi Karoly, Supervisor
401 Oversight/Express Review Permitting Unit
cc: Lauren Witherspoon. DWQ Raleigh Regional Office
US Army Corps of Engineers Raleigh Regulatory Field Office
File Copy
Central Files
Filename- 0011371-am'elHillsDam(Wake) Hold Fee Modtoh.oedPemn
Office Use Only: Form Version March 08
USACE Action ID No. DWQ No.
(It any particular item is not applicable to this project, please enter "Not Applicable" or "N/A".)
1. Processing
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
3
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:
? ?Pl
11. Applicant Information s_.
t
q
20 108
N,?J?a i 4
1. Owner/Applicant Information
Name: City of Raleigh Attn: Mr. Carl Dawson Jr PE Public Workjg ='"? `
Mailing Address: City of Raleigh
Public Works Department
PO Box 590
Raleigh NC 27602
Telephone Number:_ [phone] Fax Number: _ [phone]
E-mail Address: carl.dawsongci.raleigh.nc.us
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: Veronica High El
Company Affiliation: City of Raleigh
Mailing Address: Public Works Department Stormwater Management Division
PO Box 590
Raleigh NC 27602
Telephone Number: [phone] Fax Number:_ [phone]
E-mail Address: [e-mail]
Page 5 of 13
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: Laurel Hills Dam Spillway Upgrade
2. T.I.P. Project Number or State Project Number (NCDOT Only):
3. Property Identification Number (Tax PIN):0785895587 (3909 Rhododendron),0785893872
(3905 Rhododendron), 0785892984 (4401 Laurel Hills), 0785799725 (4300 Laurel Hills)
4. Location
County: Wake Nearest Town: Raleigh
Subdivision name (include phase/lot number): Laurel Hills
Directions to site (include road numbers, landmarks, etc.): US 70 West (Glenwood
Avenue) to Edwards Mill Road south, right onto Laurel Hills Drive, Laurel Hills lake is
located on the left near 4300 block
5. Site coordinates (Lat/Long or decimal degrees): 35° 50' 12.26"N, 78° 42' 07.58"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): I 1
7. Name of nearest receiving body of water: Unnamed Tributary into Crabtree Creek
8. River Basin: Neuse
(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/maps/.)
Page 6 of 13
9. Describe the existing conditions on the site and general land use in the vicinity of the project
at the time of this application: Laurel Hills Lake is located in a fairly developed residential
community. There is an existing public roadway along the top of the dam During several
large rain events, the dam has been overtopped and damaged due to an inadequate spillway.
10. Describe the overall project in detail, including the type of equipment to be used: Laurel
Hills Dam structure will be rehabilitated to include a new spillway structure that will meet
State Dam Safety standards. Please see the attached Laurel Hills Dam Technical
Suecifications.
11. Explain the purpose of the proposed work: The proposed to work will install a spillway
to convey flow to meet State Dam Safety Standards. Currently, the flow from the outlet pipe
discharges along the downstream slope of the dam presenting potential erosion to the dam
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. The Laurel Hills Dam Spillway Rehabilitation Project previously
Re-issued a USACE NW #3 permit (ID 200620183, expiring May 8 2010) A DWQ permit was
issued but since expired September 5, 2002 (ID 001137).
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.
The owner of the lake parcel has indicated that he would like to remove sediment from Laurel
Hills Lake that has settled into the lake due to upstream land development His proposed work is
not a part of the City of Raleigh project.
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.
Page 7 of 13
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 City of Raleigh will limit
our construction activity to approx. 120 ft upstream of the toe of the existing embankment slope,
through the existing dam embankment, to approximately 100 ft downstream of the existing
downstream toe of embankment. Most upstream and downstream project disturbance beyond the
existing embankment is due to temporary water and erosion control measures.
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,
senarately list impacts due to both structure and flooding.
Wetland Impact
Site Number
(indicate on map)
Type of Impact Type of Wetland
(e.g., forested, marsh,
herbaceous, bog, etc.) Located within
100-year
Floodplain
(yes/no) Distance to
Nearest
Stream
(linear feet) Area of
Impact
(acres)
None 0

Total Wetland Impact (acres)
3. List the total acreage (estimated) of all existing wetlands on the property: Unknown
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
Number
(indicate on map)
Stream Name
Type of Impact
Perennial Intermittent?
? Average
Stream Width
Before Impact Impact
Length
(linear feet) Area of
Impact
(acres)

1
Unnamed Tributary Channel
Stabilization
(downstream)
Perennial
5
180
0.23

Total Stream Impact (by length and acreage) 180 0.23
Page 8 of 13
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, dredaing. flooding. drainage- bulkheads. etc_
Open Water Impact
Site Number
(indicate on ma) Name Waterbody

(if ap
applicable) )
Type of Impact Type of Waterbody
(lake, pond, estuary, sound, bay,
ocean, etc.) Area of
Impact
(acres)
2 Laurel Hill Lake Temporary Fill Lake 0.64

Total Open Water Impact (acres) 0.64
6. List the cumulative impact to all Waters of the U.S_ resulting from the nroiect-
Stream Impact (acres): 0.23
Wetland Impact (acres): 0
Open Water Impact (acres): 0.64
Total Impact to Waters of the U.S. (acres) 0.87
Total Stream Impact (linear feet): 180
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.
N/A
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.): N/A
Proposed use or purpose of pond (e.g., livestock watering, irrigation, aesthetic, trout pond,
local stormwater requirement, etc.): N/A
Current land use in the vicinity of the pond: N/A
Size of watershed draining to pond: N/A Expected pond surface area: N/A
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
Page 9 of 13
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. This project is for the sole
purpose of meeting Dam Safety requirements for this classifiction of dam Because the existing
outlet device is undersized, the dam has overtopped on numerous occasions and has had to be
repaired. The proposed rehabilitation work on the dam will include adding new riser and outlet
pipes and upstream and downstream erosion/water control devices and energy dissipater.
Disturbance to existing areas will be kept to a minimum and fencing will be used to define
disturbed limits.
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
http://h2o.enr.state.nc.us/newetlands/stn-nvide.htirii.
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.
N/A; None required due to maintenance of an existing facility.
Page 10 of 13
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/wrp/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): N/A
Amount of buffer mitigation requested (square feet): N/A
Amount of Riparian wetland mitigation requested (acres): N/A
Amount of Non-riparian wetland mitigation requested (acres): N/A
Amount of Coastal wetland mitigation requested (acres): N/A
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
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 ?
Page l 1 of 13
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 4200 3 (2 for Catawba) 12600
2 0 1.5 0
Total 4200 12600
* 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 City of Raleigh considers the work
associated with this project as maintenance of an existing dam facilitv and is exempt from
mitigation requirements.
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.N/A existing proposed impervious surfaces
will be the same-
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.
N/A
XIII. Violations (required by DWQ)
Is this site in violation of DWQ Wetland Rules (15A NCAC 2H .0500) or any Buffer Rules?
Yes ? No
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
Page 12 of 13
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://h2o.enr.state.nc.us/ncwetlands. If no, please provide a short narrative description:N/A
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).
The US Army Corps has re-issued a Nationwide Permit 3 for the project expiring May 8, 2010
and a NC Dam Saftety Permit has been obtained already for the project. Funding for the repairs
is a Part of the Citv's Bond Program with a limited construction time period.
f /Z14, &//3"/L9 $
Applicant/Agent's Sifnature 0 I:f AZ 0T bate
(Agent's signature is valid only if an authorization letter from the applicant is provided.)
Page 13 of 13
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U.S. ARMY CORPS OF ENGINEERS
WILMINGTON DISTRICT
Action ID. 200620183 County: Wake
USGS Quad: Raleigh West.
GENERAL PERMIT (REGIONAL AND NATIONWIDE) VERIFICATION
Property Owner / Authorized Agent: Ms. Veronica High
Address: Citv of Raleigh
P.O. Box 590
Raleigh, NC 27602
Telephone No.: 919-890-3030
Size and location of property (water body, road name/number, town, etc.): The project site is loc _rted on the so-Ih
side of Laurel Hi II Road, between its intersections with Laurel Ridge Drive.:tnd Rhododendron Drive, \? c t of
Cree'rmoor Road, south of GlenNNood Avenue. in Wake Countv, NC.
Description of projects area and activity: This permit authorizes mechanized landclearing, excavation. the
installation of culverts. and the placement of fill associated with the reconstruction of a dam. impacts include
piping of 100LF of and unnamed tributary to Crabtree Creek.
Applicable Law: ® Section 404 (Clean Water Act, 33 USC 1344)
? Section 10 (Rivers and Harbors Act, 33 USC 403)
Authorization: Regional General Permit Number:
Nationwide Permit Number: 3
Your work is authorized by the above referenced permit provided it is accomplished in strict accordance with the
attached conditions and your submitted plans. Any violation of the attached conditions or deviation from )-our
submitted plans may subject the pennittee to a stop work order. a restoration order and/or appropriate legal action.
This verification is valid until the NWP is modified, reissued, or revoked. All of the existin-, NVt'Ps are Scheduled to
be modified, reissued, or revoked prior to March 18, 2007. It is incumbent upon you to remain informed of changes to
the NWPs. We will issue a public notice when the NWPs are reissued. Furthermore, if you commence or are under
contract to commence this activity before the date that the relevant nationwide permit is modified or revoked, Nou will
have twelve (12) months from the date of the modification or revocation of the NWP to complete the activity under the
present terms and conditions of this nationwide pen-nit. If. prior to the expiration date identified below, the nationw ide
pennit authorization is reissued and.'or modified. this verification will remain valid until the expiration date identified
below, provided it complies with all new and-'or modified terms and conditions. The District Engineer may, at an time.
exercise his discretionary authority to modify, suspend, or revoke a case specific activity's authorization under any
NWP.
Activities subject to Section 404 (as indicated above) may also require an individual Section 401 Water Quality
Certification. You should contact the NC Division of Water Quality (telephone [phone]) to determine Section
401 requirements.
For activities occurring within the twenty coastal counties subject to regulation under the Coastal Area Management
Act (CAMA). prior to beginning work %ou must contact the N.C. Division of Coastal Management.
This Department of the Army verification does not relieve the pennittee of the responsibility to obtain any other
required Federal, State or local approval s'pen-n its.
If there are any questions regarding this verification, any of the conditions of the Permit, or the Corps of Engineers
regulatory program, please contact Thomas Brown at [phone] x22.
Corps Regulatory Official _Jamie Sherri Date: Mav 8, 2008
Expiration Date of Verification: May 8. 2010
C'mw 4. ?L'

Determination of Jurisdiction:
? Based on preliminary infonnation, there appear to be waters of the US including wetlands within the above
described project area. This preliminary determination is not an appealable action under the Regulatory Program
Administrative Appeal Process ( Reference 33 CFR Part 331).
? There are Navigable Waters of the United States within the above described project area subject to the permit
requirements of Section 10 of the Rivers and Harbors Act and Section 404 of the Clean Water Act. Unless there is
a chance in the lain or our published regulations, this detennination may be relied upon for a period not to exceed
five years from the date of this notification.
There are waters of the US and,'or wetlands within the above described project area subject to the permit
requirements of Section 404 of the Clean Water Act (CWA)(33 USC § 1344). Unless there is a change in the law
or our published regulations, this determination may be relied upon for a period not to exceed live \ cars from the
date of this notification.
? The jurisdictional areas skithin the above described project area have been identified under a previous action.
Please reference jurisdictional detennination issued _. Action 1D
Basis of Jurisdictional Determination: Areas on this site exhibit wetland criteria as described in the 1987 Corps
Wetland Delineation Manual and are adiacent to an unnamed tributary to Crabtree Creek. The property
contains stream channels that exhibit an Ordinary Hioh Water Mark as indicated by changes in soil character
and absence or terrestrial yeQetation and are hydroloaicaliv connected to Cr ')tree Creek, in the Neuse Rker
Basin. .
Corps Regulatory Official:
Date May 8. 2008
SURVEY PLATS. FIELD SKETCH, WETLAND DELINEATION FORMS, PROJECT PLANS, ETC..
MUST BE ATTACHED TO THE FILE COPY OF THIS FORM, IF REQUIRED OR AVAILABLE.
Copy Furnished:
NVILMINGTON DISTRICT
POST-CONSTRUCTION COMPLIANCE FORM
Permit Number: 200620183
Permit Type. NW3
Name of County: Wake
Name of Permittee: Citv of Raleigh attn:Veronica High
Date of Issuance: May 8, 2008
Project Manager: Jamie Shern
Upon completion of the activity authorized by this permit and any mitigation required by the
permit, sign this certification and return it to the following address:
U.S. Army Corps of Engineers
Attention: CESAW-Rd-R
608 Falls of the Neuse Road Suite 120
Raleigh, North Carolina 2761
Please note that your permitted activity is subject to a compliance inspection by an U.S. Army
Corps of Engineers representative. If you fail to comply with this permit you are subject to permit
suspension, modification, or revocation.
I hereby certify that the work authorized by the above referenced pen-nit has been completed in
accordance with the terms and conditions of the said permit, and required mitigation was completed
in accordance with the permit conditions.
Signature of Permittee Date
e??
NCDENR
North Carolina Department of Environment and Natural Resources
Division of Land Resources
James D. Simons, PG, PE
Director and State Geologist
Certificate of Approval
March 6. 2008
CERTIFIED MAIL
RETURN RECEIPT
Mr. James K. Leumas, PE
Senior Stormwater Services Project Engineer
City of Raleigh Public Works Department
Post Office Box 590
Raleigh, North Carolina 27602-0590
RE: Approval to Repair
Laurel Hills Dam
Wake County
WAKE-3181
Dear Mr. Leulnas:
Michael F. Easley, Governor
William G. Ross Jr., Secretary
Citf of Rafe!?h
MAR 1 2 2008
Stormwater Management
This is in response to your submission dated November 28, 2007 and received on November 30,
2007 of plans, specifications and design data for the repair of the subject dam in compliance with
the Dam Safety Law of 1967. These plans, specifications and design data were prepared under
the supervision of Mr. J. Allen Tice, PE. This letter constitutes approval of the proposal to repair
the subject dam according to the plans and specifications received by this Division on November
30. 2007 with the following stipulations:
Mr. J. Allen Tice, PE shall provide engineering supervision.
2. During construction, the Division of Land Resources may require such progress reports
as are deemed necessary.
3. Please submit two sets of sealed, signed & dated plans, specifications and design data
prior to commencing repairs.
Geological Survey • Land Quality • Geodetic Survey
Division of Land Resources • 1612 Mail Service Center, Raleigh, North Carolina 27699-1612
512 North Salisbury Street, Raleigh, North Carolina 27604
919-733-3833 \ FAX: [phone] \ Internet: www.dlr.enr. state.nc.us/dlr.htm
An Equal Opportunity \ Affirmative Action Employer- 50% Recycled 110% Post Consumer Paper
Mr. Leumas
March 6, 2008
Page 2 of 2
4. Upon completion of the project, Mr. J. Allen Tice, PE shall inspect the completed work
and upon finding that the work has been done as specified and the dam is safe, shall file
with the Division of Land Resources two sets of record drawings and a certificate stating
that the work has been completed in accordance with approved plans, specifications and
other requirements.
4. No water shall be impounded behind the dam until final approval is issued by the
Division of Land Resources for operation of this dam. Also, draining of the lake shall be
performed in such a manner as to preclude off-site sedimentation.
5. An emergency action plan (EAP) and an operation and maintenance (O&M) plan are
required for all high hazard dams. The O&M plan should address routine maintenance,
frequency of inspections by the owner or the owner's representative, and annual
operation of the bottom drain to ensure that it is functional. It is strongly recommended
that the EAP be submitted prior to commencing repairs to deal with problems that may
arise during construction. Nevertheless, both the EAP and O&M plan must be received
prior to issuance of an approval to impound.
6. You must notify Mr. John Holley, PE, Regional Engineer, Land Quality Section, 3800
Barrett Drive, Raleigh, North Carolina 27609, [phone] ten days before the start of
construction.
The Army Corps of Engineers and the Water Quality Section of this Department should be
contacted to determine if additional permits are required. Also, the erosion and sediment control
program having jurisdiction should be contacted to determine permit requirements. In any case.
sediment must be prevented from entering the waters of the state or flowing onto neighboring
property.
Construction of the repairs must begin within one year of the date of this letter or this approval is
void. For assistance you may contact Mr. John Holley, PE, at [phone] or a staff member
of the Dam Safety Program in the Raleigh Central Office at [phone].
Sincerely,
James D. Simons, PG, PE
Director and State Geologist
JDS/tvi
cc: Mr. J. Allen Tice, PE
Mr. John Holley, PE, Regional Engineer
Surface Water Protection Regional Supervisor
JUN-20-2008 FRI 01:16 PM DENR RRO FAX NO. 19195714718 P. 01
NORTH CAROLINA
DEPARTMENT OF ENVIRONMENT
AND NATURAL RESOURCES
Raleigh Regional Office
Michael F. Easley, Governor
William G. Ross, Jr., Secretary
DIVISION OF LAND RESOURCES
April 20, 2007
LETTER OF APPROVAL
City of Raleigh
PO Box 590
Raleigh, NC 27602
ATTN: Veronica High, El
Dear Ms. High:
+ r;
NCDENR
NoRTm CAROLINA D-PARTMENT OF
ENVIRONMr-NY ANo NATURAL REsoURCk +
RE: Project Name. Laurel Hills Dam
County: Wake
Submitted by: City of Raleigh
Date Received: 4-10-07
Date Processing lnitiated:4-10-07
Watershed: Neese.
New Submittal ( ) Revised (x )
This office has reviewed the subject Erosion and Sedimentation Control Plan. We find the plan to be
acceptable and hereby issue this letter of approval. If any modifications, performance resen a:?ons, or
recornmendations are applicable, a list is enclosed and is incorporated as a part of this letter o'approval. The
enclosed Certificate of Approval should be posted at the job site. In addition, it should be not,,d that this plan
approval shall expire three (3) years following the date of approval, if no land-disturbing aeti` ity has been
undertaken, in accordance with Title 15A, North Carolina Administrative Code (NCAC) 413-0 D29.
If any modifications are not incorporated into the plan and implemented in the field; ale site will be in
violation of the Sedimentation Pollution Control Act of 1973 (North Carolina General Statute (NCGS),
113A-61,1).
15A NCAC 4}3.0018(a) requires that a copy of the approved plan be on file at the job site. Also, this
letter gives the notice required by NCGS 113A-61.1(a) concerning our right to perform period is inspections
to ensure compliance with the approved plan,
1628 Mail Service Center, Raleigh, North Carolina 27699-1628
Phone: [phone] / FAX: [phone] / Internet: www.enr.state.nc.us/ENR/
AN EQUAL OPPORTUNITY/AFFIRMATIVE ACTION EMPLOYER-60 o RECYCLED11o% POST CONSUMER PAPER
JUN-20-2008 FRI 01;16 PM DENR RRO FAX NO. 19195714718 P. 02
Nigh
April 20, 2007
Page 2
North Carolina's sedimentation pollution control program is performance oriented, r squiring
protection of the natural resources and adjoining properties. If at any time during this project it is determined
that the Erosion and Sedimentation Control Plan is inadequate to meet the requirements of the Sedimentation
Pollution Control Act of 1973 (NCGS 113A-51 through 66), this office may require revisions in the plan and
its implementation to ensure compliance with the Act.
Acceptance and approval of this plan is conditioned upon your compliance with applicable federal
and state water quality laws, regulations and rules, This could include the Division of Water Quality under
stoumwater or other specific water quality standards, and the U.S. Army Corps of Engineers tender Article
4041.urisdiction. Our approval does not supersede anv other required permit or approval,
Since this project disturbs one or more acres, one such approval relates to the stormwater that will
discharge from your project. This runoff is permitted pursuant to the National Pollutant Discharge
Elimination System (NPDES) administered in North Carolina by the Division of Water Quality (DWQ). The
General Stormwater NPDES Permit, NCG010000, as revised, covering your activity is attached, You are
responsible for complying with the General Permit requirements and are subject to enforcement by DWQ for
any violations of the General Permit.
Please note that this approval is based in part on the accuracy of the information pros ided concerning
financial responsibility- You are requested to file an amended Financial Responsibility Form if any changes
become necessary. fn addition, it would be helpful if you would notify this office when the pn oposed land-
disturbing activity covered by this plan is initiated,
Your cooperation is appreciated and we look fonvard to working with you on this project. If there are
any questions, please do not hesitate to contact this office.
Sincerely,
J hn L. Holle,/, Jb!; p.1r.,
egiolality Engineer
and Section
JLH ugh Regional Office
LAUREL HILLS DAM
TECHNICAL SPECIFICATIONS
Prepared For:
City of Raleigh
P.O. Boa 590
Raleigh. North Carolina 27602-0590
Prepared By
MACTEC Engineering and Consulting, Inc.
3301 Atlantic Avenue
Raleigh. North Carolina 27604
August 14, 2007
TABLE OF CONTENTS
PAGE
1.0 GENERAL ........................................................................................................................... 1
1.1 PROJECT ADMINISTRATION .................................................•---.............................................. 1
1.2 PROJECT (GEOTECHNICAL) ENGINEER ........................ ................... I
1.3 CONTRACTOR RESPONSIBILITIES ................. ....... ................................... ............................... 1
1.4 LIST OF DRAWINGS ................................................................................................................ 2
1.5 RELATIONSHIP OF DRAWINGS AND SPFCIFICATIONS ............................................................ 2
2.0 SPILLWAY UPGRADE ..................................................................................................... 2
2.1 GENERAL --••......................................................................................•--•-----..._..--•- -----..........2
2,2 COFFERDAM .......................... .............. ................................ ........................ ....... ................... 3
23 TEMPORARY HDPE DRAINAGE PIPE .............. _............................................5
2.4 PRINCIPAL SPILLWAY ..................... ............... .............................................. ................... ....... 7
3.0 BACKFILL ........................................................................................................................10
3.1 MATERIALS .................................. ..................................................................... .......... ........ l0
3.2 INSTALLATION .......................................... ........ ..................................................... ............. . 10
3.3 QUALITY CONTROL ............................................................................................................. I l
4.0 CONCRETE ...................................................................................................................... 11
4.1 MATERIALS ............................................................. •---••---• ---••---....-- - .......... 11
4.2 INSTALLATION ..................... ................................................... ........................ ........... .......... 11
4.3 QUALITY CONTROL ............................................. ........................ ....... ........ ..... .•-.... ............ 12
5.0 EROSION PROTECTION .............................................................................................. 12
5.1 MATERIALS .......................... ............ ......... ........ ... -••-------.................... ............................ 12
5 2 INSTALLATION .......................... ................ ..................... --............ .......................... ---........... I3
6.0 SANITARY SEWER ......................................................................................................... 15
6.1 MATERIALS ..................... .......... .............................................. .......... ----....---....................... 15
62 INSTALLATION ..................................... ............. ...-...... ----_...................... --- .......... ............ 16
7.0 POTABLE WATER .......................................................................... ...................... 16
7.1 MATERIALS ............................... ................................................... .......... ....... ....................... 16
7.2 INSTALLATION .................................................... ..............• ........ ....................... ---............. 17
8.0 FISH REMOVAL AND RESTOCKING ........................................................................ 17
8.1 REMOVAL ....................... ........ ................................................ ............................................. 17
8.2 RESTOCKING ........... ................................•---....---............----.................................................. 18
9.0 QUALITY CONTROL ........................................................................... ........ 18
SPECIFICATIONS
1.0 GENERAL
1.1 Project Administration
The project will be administered by:
City of Raleigh
P.O. Box 590
Raleigh, North Carolina 27602-0590
Attention: Ms. Veronica L. High. El
Phone: [phone]
1.2 Project Geotechnical Engineer
The Project Geotechnical Engineer is:
MACTEC Engineering and Consulting, Inc.
3301 Atlantic Avenue
Raleigh, North Carolina 27604
Attention: Mr. J. Allan Tice, P.E.
Phone: [phone]
Direct: 919-831-8052
1.3 Contractor Responsibilities
1 j Deviation from drawings and specifications shall be pre-approved by the City of Raleigh.
Zj As-built drawings shall be submitted by the contractor at the completion of the project. Two sets
of drawings shall be provided to the City of Raleigh and one set to MACTEC Engineering and
Consulting. Inc. Two additional sets of as-built drawings; signed; sealed and dated by Mr. J.
Allan Tice_ P.E., along with a letter of engineering certification will be required to be submitted
to the Division of Land Resources before an approval to impound water will be issued by the
Division of Land Resources.
The following specification/work descriptions may be implemented in any order the contractor
chooses provided there is no infringement regarding the integrity of work. delays are not
incurred. and the City of Raleigh does not object. However, specific portions of this project have
detailed construction sequences that must be adhered to and are outlined in later- sections.
4) The Contractor shall submit to City of Raleigh, prior to construction and for approval. a complete
construction schedule, proposed material staging locations, anticipated work hours, brief
description of methods used to construct the spillway and sewer work, shop drawings, and sheet
piling/shoring design.
5) Disruption of business or routine activities shall be minimized. Construction activities that may
disrupt normal business activity must be approved by the City of Raleigh. Coordinate traffic
rerouting with the City of Raleigh per plans.
1.4 List of Drawings
DRAWING TITLE DRAWING NO. DATE REVISION
Cover Sheet 6/02 0
Site Plan C-1 3/06 G
Cofferdam/Temporary HDPE Drain C-2 3/06 C
Sections/Details C- 3 3/06 E
Riser Box Construction Details C-4 3/06 C
Slide Gate Assembly Bottom Drain C-5 3106 C
Seepage Diaphragm and Erosion Control Details C-6 3/06 C
Outfall Endwall Plan C-7 9/00 A
Utility Plan and Profile U-1 3/06 B
Utility Crossing Details U-2 3/06 C
Traffic Control Plan Sheet T-I 4/03 B
Easements Map S-1 8/00 6
1.5 ' Relationship of Drawings and Specifications
The specifications are accompanied by design drawings that show the intended placement and types of
materials planned for the project. In the case of discrepancies between the drawings and specifications.
please contact the City of Raleigh Project Engineer. which will then discuss any discrepancies with the
Project Geotechnical Engineer.
2.0 SPILLWAY UPGRADE
2.1 General
A. Prior to beginning any work on the existing dam, install sediment and erosion control
measures as shown on drawings in accordance with Section 5.0. Refer to Drawing T-I for
traffic control details and coordinate implementation with the City of Raleigh.

B. Drain the pond at a rate not to exceed l foot per day by pumping or siphoning through the
existing 24-inch diameter reinforced concrete pipe (RCP) spillway and remove any
localized areas of ponded water that remain along the upstream toe that may affect
construction activities. Once the pond has been drained to the lowest level, elimination of
existing fish, if present, shall be performed as specified in Section 8.
C. Provide sump pits and pumping as required to control water- during construction of the
temporary cofferdam and HDPE drain piping.
D. Construct the cofferdam and initial section of HDPE drain as shown on the drawings in
accordance with the following specifications.
E. Collect and pump accumulated flow in the work area between the cofferdam and existing
dam through the existing 24-inch diameter R.C.P. (previous spillway) until the temporary
HDPE drainage pipe has been completely installed through the existing dam. Proper
placement of the new spillway will require a work area free of ponded surface water.
F. Use shoring, sheeting or other mechanical methods to support the excavation through the
existing embankment to allow for the placement of the temporary HDPE drainage pipe and
subsequent new spillway-
G_ Install concrete riser box, barrels, and endwall with outlet protection as shown on drawings
and in accordance with the following specifications. Precast concrete sections are
allowable, subject to City and engineer approval.
H. In fill areas, the Project Geotechnical Engineer or Project Geotechnical Engineer's
representative shall observe the subgrade prior to fill placement. Fill placement and
compaction shall be in accordance with Section 3.0.
I_ Remove cofferdam, construction entrance and sih fence.
J. Upon receiving impoundment authorization from Darn Safety, close bottom drain gate and
fill the lake.
2.2 Cofferdam
2.2.1 Materials
A. The soil fill to be placed for the cofferdam shall consist of existing suitable dam
soil or borrow soil with similar physical and engineering properties. Existing dam
soil may be reused as fill: however, some drying or wetting may be required in
order to achieve the desired compaction. Soil obtained from an on-site off-site
borrow sources shall be approved by the Project Geotechnical Engineer. At a
minimum, the following items must be provided to the Project Geotechnical
Engineer for evaluation of the proposed borrow material: soil sample, moisture
content (ASTM D2216), Wash 4200 sieve grain size analysis (ASTM D422), soil
classification, Atterberg limits (ASTM D4318) and maximum dry density and
optimum moisture content for Standard Proctor (ASTM D698). f=lowable fill
3
having a compressive strength of 200 psi may also be used for backfilling
purposes.
The liquid limit of the fill shall be less than 50, plasticity index less than 25 and
greater than 50 percent shall pass the No_200 sieve.
2.2.2 Installation
A. Excavate to the cofferdam bearing elevation shown on drawings and remove
soft/loose soil from the foundation area. Allow the Project Geotechrucal Engineer
to inspect the bottom before constructing the cofferdam. If unsuitable soils are
present, excavate or repair as directed by the engineer. Excavation slopes shall be
constructed in accordance with OSHA requirements but shall in no case be steeper
than 2(H):I(V)_
B. Place and compact soil fill in 8 to 10 inch loose lifts and compact to at least
95% of the standard Proctor maximum dry density. A minimum thickness of 2
feet is required prior to the operation of heavy equipment above the HDPE
temporary drainage pipe. Manual placement and compaction of fill may be
required beneath the pipe haunches to attain the required compaction
percentage. The maximum loose-fill thickness for manually compacted fill is 4
inches.
C. Bench into the slope surfaces as indicated on the drawings and place till material in
8 to 10 inch loose lifts along the slopes and compact to 95 percent of the Standard
Proctor maximum dry density. Scarify subgrade (approximately 2 inches deep)
prior- to the placement of fill for the next lift.
D. The cofferdam shall be constructed to the elevation shown on the drawings. A 5-
foot minimum width path along the centerline of the top of the dam should exist
upon completion of the cofferdam. The slopes of the cofferdam shall be no greater
than 2(H):1(V).
2.2.3 Quality Control
A. For backfill placed around the temporary HDPE drainage pipe; allow City of
Raleigh's testing agency to perform at least one field density test per 25 linear feet
of pipe per foot of compacted lift thickness to confirm that the desired compaction
percentage is achieved.
B. City of Raleigh's testing agency will perform at least one field density test per
each 2-500 square feet of compacted fill thickness with a minimum of one test per
lift at other locations to confirm that the desired compaction percentage is
achieved.
C. Fill that does not meet requirements shall be reworked or removed and replaced at
no cost to the City of Raleigh. Additional compaction testing shall be at the
contractor's expense.
2.2.4 Contractor Alternate
A. The contractor may propose alternate methods of handling water during the
construction that provide for handling stream base flow as well as protect the work
area from flooding during a 50-vear storm or two 10-yr storms occurring within
three davs of each other. Alternate methods can assume the existing 24-inch

spillway pipe will be available throughout the construction period. Submittal of
alternate methods must be accompanied by sufficient drawings and calculations to
allow review by the City of Raleigh and the Project Geotechnical Engineer.
2.3 Temporary HDPE Drainage Pipe
2.3.1 Material
A. Barrel
High Density Polyethylene (PE3408) Pipe (ASTM D' )3 )50/S.D.R.=3 )2.5)
Joint Connections-Butt fusion weld (ASTM D3261)
Collar (Waterstop) - 3-inch wide. 1.25-inch thick HDPE (ASTM D3350)
(Prefabricated or extrusion welded on-site in accordance with manufacturer's
specifications)
2.3.2 Installation
A. Excavate to the embankment bearing elevation shown on drawings and remove
soft/loose soil from the foundation area. Allow the Project Geotechnical Engineer
to inspect the bottom before constructing the embankment. If unsuitable soils are
present. excavate or repair as directed by the Project Geotechnical Engineer.
Excavation slopes shall be constructed in accordance with OSHA requirements but
shall in no case be steeper than 2(H): l (V).
B. Install the HDPE pipe to the elevation shown on the drawings. The bearing surface
of the pipe shall be free of debris, including rocks, stones. boulders and other items
that are deemed by the Project Geotechnical Engineer to be injurious to the pipe.
Use shoring, sheeting or other mechanical methods to support the excavation
through the existing embankment. Some existing underground utilities may remain
in service in accordance with the drawings. Existing overhead utilities (electric,
cable. telephone) are to remain in place and in service throughout the construction.
The contractor shall plan excavation support methods to avoid damage to all
existing utilities.
C. Fusion weld (ASTM D3261) barrel sections together to form a water-tight
connection in accordance with manufacturer's requirements for installation.
D. Backfill above the pipe to the proposed cofferdam elevation with fill and compact
in accordance with Section 222. Backfill placed around and beneath the pipe
haunches will require manual placement and compaction to attain the specified
compaction percentage.
2.3.3 Quality Control
A. Piping shall be tested for leaks in accordance with manufacturer's requirements
and are the only special requirements for the foundation of the temporary
procedures. Backfill placement shall be monitored and tested as outlined in
Section 3.0.
0
2.4
Principal Spillway
2.4.1 Materials
A. Riser
Reinforced Concrete (ASTM C94) having unit weight of 1 75 pounds per cubic
foot or greater
No. 5, 10 and 11 rebar reinforcing steel (ASTM A615/Grade 60)
Waterstop (Volclay-Waterstop RX101 or approved substitute)
B. Slide Gate Assembly
Waterman AC-31 Aluminum Canal Gate (15-inch diameter gate)
C. Barrels
High Density Polyethylene (PE3408) Pipe (ASTM D3350/S.D.R.=32.5)
Joint Connections-Butt fusion weld (ASTM D3261)
Collar (Waterstop) - 3-inch wide. 125-inch thick HDPE (ASTM D3350)
(Prefabricated or extrusion welded on-site in accordance with manufacturer's
specifications)
D. Endwall
Per NCDOT Standard Drawing 838.22 modified to site conditions as shown on
Drawings.
E. Seepage Diaphragm
Aggregate - NCDOT 1 S. 78M and No. 57 washed stone
Non-woven geotextile (Mirafi 170N or approved substitute) filter fabric with the
following properties:
Grab Tensile Strength (ASTM D4632): 180 lbs.
Elongation: 50%
Mullen Burst Strength (ASTM D 3786) 330 psi
Trapezoidal Tear Strength (ASTM D 4533) 75 lbs.
Puncture Strength (ASTM D 4833) 105 lbs.
AOS (ASTM D 4751) 80 (US Sieve)
Permittivity (ASTM D 4491) 1.4 sec-'
Flow Rate (ASTM D4491) 105 gaUrnin/s.f.
Geotextile filter fabric shall be free from tears, punctures or other defects and shall
be provided in plastic wrap to protect against ultraviolet rays until deployed.
F. Seepage Sea]
A geosynthetic clay liner (GCL) comprised of two lavers of Qeotexti]e with sodium
bentonite clay stitched between the textiles.
G. Soft Foundation for Riser- (Optional depending on existing conditions)
Coarse Aggregate Base Course (ABC (Type A) - NCDOT Section 1010
Table 1010-1.)
Woven geotextile (Mirafi FW 700 or approved substitute) filter fabric with the
following properties:
Wide Width Tensile Strength (ASTM D4595): 225 lb./in. (MD)
145 lb./in. (CMD)
Grab Tensile Strength (ASTM D4632): 370 tbs. (MD)
250 lbs. (CMD)
Elongation: 16% (MD)
15% (CMD)
Mullen Burst Strength (ASTM D 3786) 450 psi
Trapezoidal Tear Strength (ASTM D 4533) 100 lbs. (MD)
60 lbs. (CMD)
Puncture Strength (ASTM D 4833) 120 lbs.
AOS (ASTM D 4751) 70 (US Sieve)
Permittivity (ASTM D 4491) 0.28 sec-'
Percent Open Area (COE-02215-86) 4-6
Flow Rate (ASTM D4491) 18 gal/min/s.f.
Geotextile filter fabric shall be free from tears. punctures or other defects and
shall be provided in plastic wrap to protect against ultraviolet rays until deployed.
H. Trash Guard
No. 10 Galvanized rebar (ASTM A615/Grade 60)
Fill
The soil fill to be placed around the pipes shall be in accordance with Section 3.0
2.4.2 Installation
A. Excavate to riser bearing elevation shown on drawings and remove soft/loose soil
from riser subgrade. Excavation slopes shall be constructed in accordance with
OSHA requirements but shall in no case steeper than 2(H):] (,V,). If soft soil
conditions exist below design bearing elevation, install filter fabric and stone base
layer as shown in Soft Foundation Detail on Drawing No. C-5, for soft soil
conditions if necessary.
B. Remove sediment that may be present in the vicinity of the riser location and
dispose offsite. Sediment shall be removed from the temporary working area
upstream of the riser below the elevation of the slide Late bottom drain as shown
on the drawings and dispose offsite. This will provide a sediment collection area
in the vicinity of the riser.
C. Excavate and install barrels to elevations as shown on drawings. Bearing surface of
pipes shall be free of debris that includes rocks.. stones. boulders and other items
that are deemed by Project Geotechnical Engineer to be injurious to the pipe. Use
shoring, sheeting or other mechanical methods to support excavation. Existing
underground utilities (sewer) is to remain in service in accordance with the
drawings. Existing overhead utilities (electric, cable, telephone) may remain in
place and in service throughout the construction as per the plans. The contractor
shall plan excavation support methods to avoid damage to all existing utilities.
8
D. Sloped excavations through the dam will not be allowed except for the riser area
and the seepage diaphragm area. Contractor shall submit a plan of the excavation
support, sealed by a registered professional engineer licensed to practice in North
Carolina, at least two weeks prior to any excavation activity for review and
approval by the City and the Project Geotechnical Engineer. Approval of the plan
by the City and the Project Geotechnical Engineer does not relieve the Contractor
of responsibility for the correct construction and proper performance of the design.
Excess soil from the excavation or soil not suitable for re-use as fill material shall
be disposed offsite.
E. Cast barrels monolithically with riser box as shown on drawings. Should voids
around pipe penetrations exist following placement of concrete, place Sikaset
mortar or approved substitute in accordance with manufacturer's specifications to
fill the voids.
F. Attach the slide gate support frame to the side of the riser using threaded rod and
flat stock as shown on the drawings and install the slide gate in accordance with
the manufacturer's specifications.
G. Install remaining barrel pipe sections and terminate as shown in modified NCDOT
endwall. Fusion weld (ASTM D3261) barrel sections together to form a water-
tight connection in accordance with manufacturer's requirements for installation.
H. Install a geosythetic clay liner (GCL) measuring a minimum 5-feet wide, vertically-
against the sheetpile system and laterally within the bottom of the spillway trench,
to installing the compacted fill material and HDPE barrels. The soil along the
shoring face shall be free of deleterious material thus allowing the GCL to be fitted
against the sheetpile system. The GCL shall be placed into the trench on a l0-foot
spacing over the length of the sheetpile section. The lateral section of GCL shall
extend a minimum of 10 feet into the trench and shall be securely covered with
compacted fill material, such that it does not pull loose when the sheetpiling is
extracted. The GCL should be kept dry during installation, but should not be
wrapped in plastic.
Backfill to the proposed pond bottom elevation around riser and to the seepage
diaphragm subgrade elevation around barrels, if necessary, with soil fill in
accordance with Section 3.0. Backfill placed around and beneath the pipe
haunches will require manual placement and compaction to attain the specified
compaction percentage.
J. Place filter fabric for seepage diaphragm on prepared smooth subgrade and along
the pipe excavation side slopes loosely and without wrinkles. Fabric alignment
(long side) should be perpendicular to the pipe alignment.
K. Overlap adjacent sections of fabric a minimum of 2 feet with upstream sections on
top of downstream sections. Nog rings or temporary pins can be used to hold the
overlap sections.
L. Install stone/aggregate as shown on drawings.
9
M. Fold the ends of the fabric over the top of the stone/aggregate. Install additional
fabric if needed to completely cover the stone and aggregate. Special care should
be taken to ensure that the fabric completely covers the aggregate at the upstream
end of the seepage diaphragm. Leave outlet end of drainage stone open and protect
outlet end from contamination with soil fill.
N. Place and compact soil fill above the seepage diaphragm in accordance with
Section 3.0 to tie in with original ground contours. Road section shall match
existing road section in accordance with City of Raleigh requirements.
3.0 BACKFILL
3.1 Materials
A. The soil fill to be placed around the riser and barrels shall consist of existing dam
soil or borrow soil with similar physical and engineering properties. Existing dam
soil may be reused as fill; however. some off-site drying may be required in order
to achieve the desired compaction. Soil obtained from an off-site borrow source
shall be approved by the Project Engineer prior to use in the dam embankment. At
a minimum, the following items must be provided to the Project Geotechnical
Engineer for evaluation of the proposed borrow material; Soil sample, moisture
content (ASTM D2216), Wash #200 sieve grain size analysis (ASTM D422), soil
classification. Atterberg limits (ASTM D4318) and maximum dry density and
optimum moisture content for Standard Proctor (ASTM D698). Flowable fill
having a compressive strength of 200 psi may also be used for backfilling
purposes.
The liquid limit shall be less than 50. plasticity index less than 25. and greater than
50 percent shall pass the No.200 sieve.
3.2 Installation
A. Backfill around most of the barrel pipe lengths will consist of compacted soil fill.
The seepage diaphragm will serve as the majority of backfill around the final 30
feet of the barrel pipes as shown on the drawings. Placement of' soil fill and
construction of the seepage diaphragm will occur concurrently.
B. Place and compact soil fill in 8 to 10 inch loose lifts and compact to at least 95%
of the standard Proctor maximum dry density. A minimum thickness of 2 feet is
required prior to the operation of heavy equipment above the pipe. Manual
placement and compaction of fill may be required beneath the pipe haunches to
attain the required compaction percentage. The maximum loose-fill thickness for
manually compacted fill is 4 inches.
C. Bench into the slope surfaces as indicated on the drawings and place fill material
in 8 to 10 inch loose lifts along the slopes and compact to 95 percent of the
Standard Proctor maximum dry density. Scarify subgrade (approximately 2 inches
deep) prior to placement of fill.
10
3.3 Quality Control
A. For backfill placed around spillway barrels, seepage diaphragms and slope drain,
allow City of Raleigh's testing agency to perform at least one field density test per
25 linear feet of pipe per foot of lift thickness to confirm that the desired
compaction percentage is achieved.
B. City of Raleigh's testing agency will perform at least one field density test per
each 2.500 square feet of compacted fill thickness with a minimum of one test per
lift at other locations to confirm that the desired compaction percentage is
achieved.
C. Fill that does not meet requirements shall be reworked or removed and replaced at
no cost to the City of Raleigh. Additional compaction testing shall be at the
contractor's expense.
4.0 CONCRETE
4.1 Materials
A. Ready-mixed concrete is defined in this specification as concrete produced
regularly by a commercial establishment and delivered to the purchaser in the
plastic state. Concrete shall have a 28-day compressive strength of 3000 psi.
Slump shall be between 3 and 5 inches in accordance with ASTM C 143. Provide
4 to 6 percent air entrainment. Concrete used in the riser structure shall have a
unit weight of 175 pounds per cubic foot or greater.
B. Concrete shall be formed, placed and cured in accordance with applicable
requirements outlined in American Concrete Institute (ACI) and American Society
for Testing and Materials (ASTM) standards including ACI 301. 302, 308 and
ASTM C 171. C309 and D2103.
4.2 Installation
A. Provide batch ticket information for each load of ready mix concrete. Do not place
concrete when weather conditions prevent proper placement and consolidation; in
uncovered areas during periods of precipitation. or in debris- and water from
within the forms. Consolidate concrete with high frequency. internal.. mechanical
vibrating equipment supplemented by hand spading and tamping.
B. Provide and maintain 50 degrees F minimum concrete temperature. Do not place
concrete when the ambient temperature is below 40 degrees F. Cover concrete
and provide with a source of heat sufficient to maintain 50 degrees F minimum
while curing.
C. Concrete temperature from initial mixing through final cure shall not exceed 90
degrees F. Shade the fresh concrete and start curing as soon as the surface of the
fresh concrete is sufficiently hard to permit curing without damage.
D. Repair formed surfaces by removing minor honeycombs, pits greater than 1 square
inch surface area or 0.25 inch maximum depth, or otherwise defective areas.
Patch with Sikaset mortar or approved substitute in accordance with
manufacturer's requirements. Patch defects when the forms are removed.
Concrete with extensive honeycomb (including cold joints, entrapped debris,
separated aggregate, or other defects) will be rejected at the City's or the Project
Geotechnical Engineer's discretion. Obtain approval of corrective action prior to
repair. The surface of the concrete shall not vary more than the allowable
tolerances of ACI 301. Exposed surfaces shall be uniform in appearance.
E. Protect concrete from injurious action by sun, rain, wind, flowing water, frost,
mechanical injury, tire marks, and oil stains. Do not allow concrete to dry out
from time of placement until the expiration of the curing period. Forms may be
rennoved 72 hours after concrete placement.
4.3 Quality Control
A. Allow the City of Raleigh's testing agency to collect samples of fresh concrete at
commencement of each concrete placement and for each batch (minimum) or
every 10 cubic yards (maximum) of concrete for tests of air entrainment or slump
and . for the riser structure, unit weight. Fresh concrete that does not meet the
testing criteria outlined in Sections 4.1 and 4.2 shall be removed and replaced with
concrete that meets the criteria at no cost to the City of Raleigh.
B. City of Raleigh's testing agency will prepare four 6-inch diameter, 12-inch long
cylinders of fresh concrete for each sampling event. The test cylinders will be
tested in unconfined compression as follows: one cylinder after 7 days and two
cylinders after 28 days. The fourth cylinder shall be held in reserve pending the
outcome of the 28-day tests.
5.0 EROSION PROTECTION
5.1 Materials
A. Riprap
Class B Erosion Control Stone (d50 = 8 inches)
2. Erosion Control Stone meeting the following requirements; minimum of`
18 inches. midrange of 27 inches. maximum of 42 inches- and containing
12
no more than 5% smaller than the minimum or 10% larger than the
maximum
B
C.
Woven geotextile filter fabric (Miraf FW 700 or approved substitute) with the
following properties:
Wide Width Tensile Strength (ASTM D4595):
Grab Tensile Strength (ASTM D4632):
Elongation:
Mullen Burst Strength (ASTM D 3786)
Trapezoidal Tear Strength (ASTM D 4533)
Puncture Strength (ASTM D 4833)
AOS (ASTM D 4751)
Permittivity (ASTivi B 4491
Percent Open Area (COE-02 215-86)
Flow Rate (ASTM D4491)
225 lb./in.(MD)
145 lb./in. (CND)
370 lbs. (MD)
250 lbs. (CMD)
16% (MD)
15% (CMD)
450 psi
100 lbs. (MD)
60 lbs. (CMD)
120 lbs.
70 (US Sieve)
0.28 sec-)
4-6
18 gal/min/s.f.
Geotextile filter fabric shall be free from tears, punctures or other defects and shall
be provided in plastic wrap to protect against ultraviolet rays until deployed.
Silt Fence - Wooden posts. woven wire and filter fabric that meets requirements
of NCDOT Section 1605-2.
5.2 Installation
5.2.1 Temporary
Prior to beginning any ground disturbing activity, install silt fence and
temporary sediment trap at locations shown on drawings.
Inspect silt fence and sediment trap after each rain event and promptly repair
damaged sections or remove accumulated silt. Seed finished grade areas as
necessary to provide temporary cover during construction. Reseed as necessary
to maintain cover on finished grades. The contractor may propose for the
Project Geotecbmcal Engineer and City of Raleigh approved alternative siltation
protection in the vicinity of the original streambed if he deems it necessary to
improve the work area available.
13
5.2.2 Permanent
A. The contractor is required to establish permanent ground cover in
accordance with the permanent seeding specifications that is sufficient,
in the opinion of the City of Raleigh, to retain erosion. If permanent
seeding is to be performed outside the recommended seeding dates.
contained in the specifications; then the contractor shall establish and
maintain groundcover in . accordance with the temporary seeding
specifications until permanent vegetative cover can be established.
Seed repair areas with permanent cover after construction in accordance
with the following.
Vegetate the dam crest (excluding roadway), downstream slope
(to edge of riprap) and finished slope drain channel surface with
drought tolerant grass as described in this section.
a. The completed fill surfaces shall be scarified to a depth
of at least 6 inches prior to seeding.
b. Agricultural lime shall be applied at a rate of 2 tons per
acre or according to soil tests.
C. Fertilizer shall be applied at a rate of 1,000 pounds per
acre.
d. Superphosphate shall be applied at a rate of 500 pounds
per acre.
e. Till the soil after applying lime, fertilizer and
superphosphate to obtain a reasonably uniform mixture.
f. Seed using one of the following mixtures as appropriate
to the time of year the seeding is done.
August 25 - September 15
Blend of 50% KY-31 tall fescue and 50% mixture of two or more turf-type tall fescues,
or a blend of 3 or more turf type tall fescues 250 lbs./acre
Temporary Seeding (if required)
Prepare the seed bed as directed above and seed according to the following dates and
varieties.
January I - May I
May I - August 15
Annual Rye (grain) 120 Ibs/acre
Kobe Lespedeza 50 Ibs/acre
German Millet 40 lbs/acre
14
August 15 - December 15
Annual Rye (grain) 120 lbs/acre
Broadcast seed to obtain reasonably uniform coverage or apply using hydro mulch or
spray techniques.
B. Place one layer of NCDOT Class B erosion control stone on the top and
up the dam side slope of the newly graded slope drainage swale and
between the swale entrance and the driveway culvert as shown on the
drawings in accordance with the following.
Place filter fabric on smooth prepared subgrade loosely and
without wrinkles.
2. Overlap adjacent sections of fabric a minimum of 2 feet. Hog
rings or temporary pins can be used to hold the overlap sections.
3. Place a minimum of 4 inches of NCDOT No. 57 stone cushion on
fabric prior to placement of Class B erosion control stone as
shown on drawings.
Note: Riprap used to construct the temporary sediment trap may be reused
as riprap lining in the bottom layer of the output dissipater and other
appropriate locations at the site following stabilization of disturbed areas
that drain into the basin, if approved by the City.
C. Place a final layer of rip-rap (d50 = 27 inches) as shown on drawings that
extends 60 feet downstream from the outlet end of the endwall using same
procedures as described in Section 522.B. Prior to placing final riprap in
the receiving channel, remove excess sediment that may have
accumulated during construction.
6.0 SANITARY SEWER
6.1 Materials
A. Sewer pipe - Pressure Class 50 ductile iron pipe and fittings for sewer mains
and Schedule 40 PVC pipe for sewer service ]]ties meeting the requirements of
the City of' Raleigh Public Utilities Department (PUD) Manual standard
specifications and details.
B. Manholes and Related Materials - Precast, reinforced concrete meeting the
requirements of the City of Raleigh standard specifications and details.
Is
6.2 Installation
A. Install sewer and manholes as shown on drawings and in conformance with the
requirements of the City of Raleigh PUD Manual standard specifications and
details. Confirm ground surface elevations at manhole locations at time of
construction and adjust rim elevations as necessary to be flush with pavement
surface in roads and a minimum of 12 inches above ground in easements.
B. Install aerial crossing across the area to be excavated for the spillway pipes
using City of Raleigh PUD Manual standard details S-10, 5-11, S-12, S-13. S-
14, S-18 and S-19. Exceptions: No riprap is required. Concrete supports may
be placed directly under the pipe with no minimum embedment and no pier.
Distance between edge of support footing and edge of excavation support shall
be at least 5 feet.
C. All bedding and backfill material for sewer installation within the limits of the
existing dam shall be low permeability soil. or flowable fill as approved by the
Project Geotechnical Engineer. Sand or clean stone will not be allowed.
D. Place and compact bedding and backfill material in accordance with the
requirements of the City of Raleigh PUD Manual standard specifications and
details, except within the dam embankment which must meet the requirements
as specified in Section 3.0. No stone bedding may be used through the dam
except through the filter drainage diaphragm.
E. Sequence sewer construction so new manholes and sewer lines are in place
before constructing aerial section. Maintain sewer flow in existing lines
throughout construction period. Bypassing of sanitary sewage flows will be
allowed for no more than 8 consecutive hours to remove Manhole 1, install
connection to new Manhole IA and install aerial section. Provide 48 hour
advance notice to City of Raleigh of interruption schedule. The bypass is
incidental to the sanitary sewer project.
F. Install a Schedule 40 PVC sewer service line as indicated on Drawing U-1 at
manhole ID. The location shown is approximate and will be field adjusted so
the embedment depth is a minimum of 3 feet below the drainage ditch that
parallels Laurel Hills Road and so the end of the line will extend to the existing
right-of-way line. A standard Schedule 40 PVC wye and cleanout shall be
installed on the right-of-way line.
7.0 POTABLE WATER
7.1 Materials
A. Potable Water Pipe - Ductile iron pipe meeting the requirements of the City of'
Raleigh PUD Manual standard specifications and details.
16
7.2 Installation
B. Install cased temporary 6-inch water line or cased 12-inch water line as shown
on drawings and in conformance with the requirements of the City of Raleigh
standard specifications and details. Once construction is complete, the final
water line size is to be no less than 12-inch inside diameter and shall be installed
a minimum depth of j feet from the surface.
C. Install aerial crossing across the area to be excavated for the spillway pipes
using City of Raleigh standard details S-10. S-11, S-127 S-13, S-14, S-18 and S-
19. Exceptions: No riprap is required. Concrete supports may be placed
directly under the pipe with no minimum embedment and no pier. Distance
between edge of support footing and edge of excavation support shall be at least
5 feet.
D. All bedding and backfill material for water line installation within the limits of
the existing dam shall be low permeability soil. or flowable fill as approved by
the Project Geotechnical Engineer. Sand or clean stone will not be allowed
through the dam embankment.
E. Place and compact bedding and backfill material in accordance with the
requirements of the City of Raleigh PUD Manual standard specifications and
details.
F. Provide 48 hour advance notice to City of Raleigh of interruption schedule.
8.0 FISH REMOVAL AND RESTOCKING
8.1 Removal
A. If fish are present in the Laurel Hills Pond, the contractor shall remove them
during lake draining by trapping or toxifying the water with Rotenone as
detailed in chapter 2 of the Pond Management Guide. published by the North
Carolina Cooperative Extension Service. The procedure for fish removal and
restocking is outlined in detail in this guide. Once construction has been
completed and the pond refilled- the pond can be restocked with desired fish.
Draining and removal of fish will be incidental to the overflow structure project.
The uide and additional information is available online at.-
C,
://W?,V ??.CeS.ncsu.edu/nreos/wile[%fislieries,,index.litml or from:
Jim Rice
Extension Fisheries Specialist
NC State University
Zoology Department
Rm 3 Clark Labs. 919-515-4592
Raleigh, NC 27695-7617
jim rice:a;ncsu.edu.
17
8.2 Restocking
B. The contractor shall restock the pond using a balanced population of native fish;
similar to that seen when the pond is drained. The fish will be restocked as
directed in Chapter 2 of the Pond Management Guide. Depending on the time
of project completion, restocking may need to be postponed until the October or
November months, or as indicated by the Cooperative Extension Service or the
Wildlife Resources Commission. If this delay in stocking is needed, the
contractor or his representative shall be responsible for restocking at the
appropriate time. Restocking the pond will be incidental the overflow structure
project.
9.0 QUALITY CONTROL
A. Quality control will be the responsibility of the City of Raleigh or the City of Raleigh's
representative(s). Implementation of the quality control measures outlined in the previous
sections will be at the direction of the City of Raleigh. In addition to the specific quality
control measures outlined in the preceding sections for certain tasks, the Project Engineer
or the Project Engineer's representative(s) plan to visit the site periodically to view the
overall construction process and confirm that the dam improvements are being constructed
in accordance with the intent of the plans and specifications. This will include verifying
that the specified materials and construction procedures are being followed.
18
LAUREL HILLS DAM REPAIRS
MACTEC PROJECT 30720-08-3090
ANTI-FLOTATION CALCULATION
6.5 fl
92.07
7-7 7-7 NEI

i

i

\ 30.17 ft
20 ft PLAN
CROSS SECTION base thickness, 2.25 ft
Note: Concrete Unit Weight is 175 lbs/ff
U li t
F,=V.y,N
F„- 30.17x20x23.32x62.4=878.0 kips
Submerged Weight of Riser
V,=2x(211.07x 153+21.07x30.17)x(28/12)+20x30.17x2.25=5822fr
W c- V c •Yconc
Wc? 5822 x 175 1018.8 kips
Factor- of Safety
FS = 1018.8 / 878.0 = 1.16
Calculations by.- Date: 2007
Checked by: I ` Date: f ?0