SW7050724_HISTORICAL FILE_20051028

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
SW�'7C���('ZA Y
DOC TYPE
❑ CURRENT PERMIT
❑ APPROVED PLANS
HISTORICAL FILE
DOC DATE
YYYYMMDD
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H. LOWRY TRIBBLE, 1R., PE
WILLIAM F. HODGES, PE
HAROLD L. NEWBERRY, PE
J..STEVEN HARBIN, PE
W. M ICHA EL STUBBS, PE
HODGES, HARBIN, NEWBERRY & TRIBBLE, INC.
CONSULTING ENGINEERS
484 MULBERRY STREET • SUITE 265 • MACON, GEORGIA 31201
P. O. Box 974 • MACON, GEORGIA 31202 -0974
October 25, 2005
Mr. William J. Moore
North Carolina Division of Water Quality
Washington Regional Office
943 Washington Square Mall
Washington, NC 27889
Re: East Carolina Regional MSW Landfill
Phase ,4.— Stornmater Management Permit
U. 1NT'Project No. 1001-354-01 1 1001-100-07
Dear Mr. Moore:
TELEPHONE. [phone]
FAX [phone]
OCT 2 8 2005
DWQ-WARD
In respallse to your letter, dated October 12, 2005 requesting additional information, we have
made the following changes to the }flans for your review and approval:
a. Wet Detention Basin No. 2 and Wet Detention Basin No. 3 have been modified to
include a 6:1 perimeter shelf.
h. The outlet structures for both Wet Detention Basins have been modified to allow for a
4 — 5 clay drawdown of the design storm.
c. Wet Detention Basin No. 3 has been enVarged to meet the Minimum surface area
"= I'eC1111 E'enleilt5.
We have enclosed two (2) copies of the revised Stormwater Management Plan, Design
Calculation, and Technical Specifications Narrative, and two (2) copies of the revised Phase 4
Stormwater Management Plans for your use.
Should you.h'ave any questions, please call.
Sincerely,
HODGES_, U1,A1RB N, NEW13ERIZY & TRIBBLE, INC.
William F' Had cs, .E.
Professional Engn er
WhH/jhil
cc: Ray Hoffman, P.E., wI enclosure
Bill Cooksey, w/ enclosure
Michael Stubbs. P.E., w/o enclosure
Matt Check, w/o enclosure

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TABLE OF CONTENTS
1. NARRATIVE
2. STORMWATER MANAGEMENT CALCULATIONS
a.
Design Assumptions
b.
Landfill Side Slope Drainage Berm and Riser Design
C.
Downdrain Calculations
d.
Stormwater Conveyance Channel (SCC) Calculations
e.
Drop Inlets, Pipes and Headwalls
f.
Outlet Protection Calculations
3. WET DETENTION BASIN NO. 2
a. Wet Detention Basin Design Criteria
b. Design Calculations
C. Wet Detention Basin Dewatering of First 1" of Runoff
d. Permanent Pool Surface Area
C. Reservoir Routing
f. Sediment Trapping Efficiency (E&S Manual)
g. Riser Pipe and Carrier Pipe Design
h. Anti -Seep Collar Design
i. Riser Base Foundation Design
4. WET DETENTION BASIN NO. 3
a. Wet Detention Basin Design Criteria
b. Design Calculations
C. Wet Detention Basin Dewatering of First I" of Runoff
d. Permanent Pool Surface Area
e. Reservoir Routing
f Sediment Trapping Efficiency (E&S Manual)
g. Riser Pipe and Carrier Pipe Design
h. Anti -Seep Collar Design
i. Riser Base Foundation Design
5. TECHNICAL SPECIFICATIONS
a. 01560 Erosion and Sediment Control
b. 02110 Clearing and Grubbing
C. 02210 Grading
d. 02930 Grassing
6. APPENDIX
a. Location Map
b. Stormwater Management Plans
OCT 2 a 201�3
DWQ-WARO

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WINDSOR
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BERTIE COUNTY, NORTH CAROLINA

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b. Stormwater Management Plans
Sheet No. Name of Sheet
--
Title Sheet
I
Existing Topographic Survey
2
Top of Clay Liner Grading Plan
3
Final Drainage Plan
4
Erosion Control Plan
5
Drainage Basin Map
6-7
Miscellaneous Details
Revised: October 2005 East Carolina Regional Landfill
HHNI" Project No, 1001-354-01 Phase 4 Construction Permit— Stormwater Management Plan
51

1. NARRATIVE
® The East Carolina Regional MSW Landfill (MSWLF) is an existing municipal solid waste
landfill located in Bertie County, North Carolina. Approximately 71 acres of the landfill
footprint is currently constructed. Phase 4 development of the landfill will disturb
approximately 51 acres. Of this disturbed area approximately 25 acres will represent the
actual footprint of the waste disposal cells and approximately 26 acres will represent areas
for access road, buildings, support facilities, forebays, wet detention basins, and outside
slopes along cut and fill areas around the landfill. Efforts have been made in the design of
this facility to minimize the total disturbed area. Disturbed areas will be stabilized using
erosion control measures. Stormwater which comes from off -site and undisturbed areas on -
site will be diverted around the MSWLF. Precipitation which falls onto the MSWLF will be
drained to and transported by stormwater conveyance channels (SCC) to one of two wet
detention basins. These basins are designed to protect water quality by reducing the
stormwater runoff rate and removing total suspended solids (TSS) from stormwater runoff.
These basins, as well as a timely application of various erosion and sedimentation practices,
will minimize the time that soils are exposed, control stormwater runoff, protect soils from
erosive forces, protect surrounding property and preserve water quality. Below is a detailed
description of the stormwater, erosion and sedimentation control techniques to be used at the
MSWLF to protect the site and surrounding property.
The best way to control sediment is to minimize erosion at its source. One way to minimize
erosion is to control stormwater through the use of stormwater management structures in
areas of concentrated water flows. In the design ofa landfill, stormwater must be controlled,
collected and transported from the top of the landfill to the point where it exits the property.
Stormwater which falls onto the top of a landfill or along its side slopes, will be collected by
a series of side slope diversion berms and side slope downdrain pipes. Side slope diversion
berms are vegetated earthen structures constructed across the landfill side slope. These are
spaced every 20 - 40 vertical feet on the landfill side slope. The side slope diversion berms
are constructed a minimum of 2' high and at a 2% slope along the stormwater pathway. The
purpose of the side slope diversion berm is to reduce the slope length that stormwater runoff
will travel as sheet flow, and move the stormwater to a side slope downdrain pipe.
All landfill side slopes and berms will be grassed. Berms will be lined with a temporary
liner, such as Excelsior Matting for temporary protection prior to pennanent vegetation being
established. The side slope downdrain pipes will be used to transport runoff from points on
the landfill to the bottom. These pipes will be 24" diameter corrugated HDPE pipe and will
be sized to carry the runoff collected behind each berm while not exceeding 60% of the
capacity of the 24" diameter pipe. The downdrain pipes will discharge into a stabilized open
stormwater conveyance channel (SCC) system or directly into a drop inlet structure. A rip -
rap apron will be placed at the outlet of each downdrain system to reduce the velocity of the
concentrated pipe flow and prevent erosion at the outlet as it enters the stabilized SCC
system at the toe of the waste footprint.
Revised: October, 2005 East Carolina Regional Landfill
HHNT Project No. 1001-354-01 Phase 4 Construction Permit — Stormwater Management Plan
i

The SCC system around the waste footprint collects all of the stormwater runoff from the
outside edge of the access road around the landfill to the top of the landfill. These SCCs are
2' wide at the bottom, 4' deep and have 2:1 side slopes. All SCCs will be grassed. If
velocities exceed 2 feet per second (i.e. scour velocity), temporary and/or permanent
protective measures will be used to prevent scouring. These measures include temporary
liners which are used to protect the SCC until the grass has time to grow and mature, and
permanent SCC liners, such as stone rip -rap, concrete or special geotextile materials. These
liners are discussed further in Section (e) of this document.
The stormwater runofflias now been taken from areas on the landfill, along grassed diversion
berms, through the downdrain pipe systems to the SCC system. The SCC system transports
the stormwater by gravity to two wet detention basins. The stormwater is collected in drop
inlets and transported across the access road and into the wet detention basins through
drainage pipes. The inlets and pipes are sized to handle the 25 year - 24 hour storni event.
Temporary drop inlet protections in the forms of sediment traps and silt fences are used
around the drop inlet to collect sediment from upstream SCCs. These protections help keep
sediment out of the drainage pipe system. The outlet of each drainage pipe entering the wet
detention basins is also protected from soil scouring with a stone rip -rap apron.
Two wet detention basins are to be used for final trapping and settlement of sediment. The
basins are designed in accordance with the NCDENR Stormwater Best Management
Practices Manual. Specific design specifications for each basin are included in this
document.
Based on the topography of the site and the design of the landfill, there are areas that will be
disturbed and the stormwater runoff from these areas can not be diverted to one of the two
wet detention basins. These areas include the outside cut and fill slopes on access roads and
the wet detention basins. In order to control stormwater runoff and control erosion and
sedimentation, all of these areas will be protected by the installation of silt fencing as well as
being mulched and vegetated. Mulch helps to reduce runoff and erosion, conserve soil
moisture, and prevent soil compaction and crusting. Each of these areas will be stabilized by
using temporary and permanent grassing along with slope protective materials, such as
Excelsior Matting, permanent erosion control pre -seeded blankets, channel liners, other types
of erosion control blankets and mats, or a sprayed -on synthetic polyacrylamide polyamine
"Silt Stop", if required. The polyamine chemically binds to the fine clay particles and
prevents the particles from going into solution. In addition to the use of mulch, grassing and
slope protective materials, all areas downhill of a disturbed area will be protected with silt
fencing. Silt fencing will capture sediment and prevent it from leaving the site and entering
any drainageways.
Revised: October, 2005 East Carolina Regional Landfill
HHNT Project No. 1001-354-01 Phase 4 Construction Pemi t — Stormwater Management Plan
2

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Erosion and sedimentation control measures will be inspected routinely and after any
significant rainfall events. Any damage observed will be repaired. Cleanout of sediment
control structures will occur regularly to maintain the effectiveness of the structures.
Sediment removed from these structures will be used as cover soils for the landfill waste.
Silt fencing and drop inlet protection will remain in place until sediment contributing areas
are stabilized.
The site manager of the MSWLF will be responsible for the facility stonnwater, erosion and
sedimentation control program. The address and telephone number of the manager is listed
below:
Mr. Bill Cooksey
Republic Services of North Carolina, LLC
East Carolina Regional Landfill
1922 Republican Road
Aulander, NC 27805
Phone: [phone]
Revised: October, 2005 East Carolina Regional Landfill
HHNT Project No. 1001-354-01 Phase 4 Construction Permit— Stormwater Management Plan
3

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2. STORMWATER MANAGEMENT CALCULATIONS
Revised: October, 2005
HHNT Project No. 1001-354-01
East Carolina Regional Landfill
Phase 4 Construction Permit — Stormwater Management Plan
4

a. Design Assumptions
The following assumptions are used to size all downdrains, side slope berms, stormwater
conveyance channels (SCC), and storm piping.
1) It is assumed that the surface of the landfill is 50% impervious. This fairly represents
the observed amount of runoff from many closed landfills in the southeastern United
States.
2) Downdrains are designed to flow approximately 60% full during the 25 year - 24
hour storm event. All proposed downdrain pipes are 24" diameter and all risers are
18" — 24" diameter.
3) Downdrain calculations are based on corrugated plastic pipe.
4) Stortn drainage flows were calculated using HYDRAFLOW and the SCS Method.
5) The Curve Number CN = 74
6) Estimated velocities of storm water:
5% slope on top of landfill
= 1.5 fps
along side slope berms
= 3.0 fps
in downdrain pipes
= 12 fps
down 3.5:1 side slopes
= 3.9 fps
7) Side slope drainage berms shall be 24" deep and designed with a minimum of 2%
slope.
8) Perimeter SCC shall be designed with a 2' minimum bottom width and 2:1 side
slopes.
9) SCC with greater than 2.0 fps velocity shall be designed with SCC stabilization.
10) Shear stress for temporary ground cover in SCCs where the velocity exceeds 2.0 fps,
shall be calculated to determine the type of SCC stabilization to be used.
T=yxdxs
y = 62.4 Ws. f.
d = depth of flow
s = slope of SCC, ft./ft.
is Revised: October, 2005 East Carolina Regional Landfill
HHNT Project No. 1001-354-01 Phase 4 Construction Permit — Stormwater Management Plan
5

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11) Drop inlets shall be designed with a 4 foot square minimum inside dimension and
18" high opening on all 4 sides.
12) Manning's "n" for corrugated plastic downdrain pipe is:
12"-0.018 21"-0.020
15" - 0.018 24" - 0.020
18" - 0.020
13) Manning's "n" for concrete pipe is 0.013.
14) Manning "n" for corrugated metal pipe is 0.023.
15) See "Erosion Control Plan" sheet in the Phase 4 Engineering Plans for Drainage
Structure Locations.
Revised: October, 2005
HHNT Project No. 1001-354-01
East Carolina Regional Landfill
Phase 4 Construction Permit — Stormwater Management Plan
6