ACP Fayetteville Contractor Tard - CY10A - 09.11.2018 SUBMITTAL NCDEQ Submission

ATTACHMENTS

ATTACHMENT 1

Project Description

NCDEQ Stormwater Permit Application
Stormwater Project No. SW6180702
ACP Fayetteville Contractor Yard – CY10a
Cumberland County, North Carolina
S&ME Project No. 7235-17-008
Project Information
Atlantic Coast Pipeline (Dominion Energy Transmission Inc.) is proposing to construct a contractor staging area off
Downey Road, Fayetteville. The site crosses two parcels as shown on the attached USGS Site Overview Map. The
property deeds to these parcels have been included in the attachments.
The existing condition is covered with well vegetated grass with some woods located in the west. The site has very
mild slopes with a peak contour of 96’ and a low of 92’ over 34.6 acres. The soils on site belong to different
hydrologic soil groups and have varying water table levels. This is described in more detail in the attached Soil
Report by S&EC as well as S&ME’s Stormwater Wetlands Calculation Report.
The construction of the proposed contractor staging area will require attenuation for the 1-year, 24-hour storm as
well as significant TSS removal. The existing topography creates four drainage areas. However, as seen in the
attached Stormwater Wetlands Calculation Report, after construction the site has only two drainage areas which
will greatly influence where the stormwater control measures can be located. Due to the high seasonal high water
table (see attached Soils Report by S&EC) and topographic site constraints, two stormwater wetlands are
proposed as stormwater control measures for the proposed contractor staging area.
In the northwest, Stormwater Wetland 222S will collect approximately 20 percent of the site’s drainage and will
release this treated runoff into the adjacent road’s ditch. In the south, Stormwater Wetland 221S will collect
approximately 80 percent of the site’s drainage and will slowly release this treated runoff into the adjacent
wetland to assure the wetland is not negatively affected by the site’s construction. The locations and technical
details of these stormwater wetlands can be found in the attached drawing set for the proposed stormwater
design.
For a summary of the stormwater control measures and their operations and maintenance, please refer to the
attached supplemental BMP and O&M forms.

ATTACHMENT 2

USGS Site Overview Map
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INDIANCREEK DRBANDORECI
RP IN P O IN T R D DRAPER RDA N G E L I A M S T
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RRIVANNA DRNED ASHLEY RDH U G H E S R D ACCORD RDNC HWY 24
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CLINTON RDDOWNING RDCopyright:© 2013 National Geographic Society, i-cubed
^_Dominio n C ontra ctor Yard 10A Entrance
Contractor Yard 10A Boundary
Streets
Ta x Parcels
SCALE:
DATE:
PROJECT NUMBER
FIGURE NO.
11 " = 1,000 '
8-29-18
7235-17-008
CONTRACTOR YARD 10ACUMBERLAND COUNTYNORTH CAROLINADrawing Path: Q:\7235\17\008 Dominion - ACP Contractor Yards\Cumberland Site\GIS\Cumberland USGS Map.mxd plotted by jtayouga 08-29-20180 1,000 2,000(FE ET)
USGS SITE OVERVIEW MAP
³
REFERENCE:GIS BASE LAYERS WERE OBTAINED FROM ESRI, USGS, CUMBERLAND COUNTY, ANDDOMINION. THIS MAP IS FOR INFORMATIONAL PURPOSES ONLY. ALL FEATURELOCATIONS DISPLAYED ARE APPROXIMATED. THEY ARE NOT BASED ON CIVIL SURVEYINFORMATION, UNLESS STATED OTHERWISE.

ATTACHMENT 3

Stormwater Management Permit Application Form

DEMLR USE ONLY
Date Received Fee Paid Permit Number

Applicable Rules:  Coastal SW – 1995  Coastal SW – 2008  Ph II - Post Construction
(select all that apply)  Non-Coastal SW- HQW/ORW Waters  Universal Stormwater Management Plan
 Other WQ Mgmt Plan:

Form SWU-101 Version Oct. 31, 2013 Page 1 of 6 1Updated Stormwater Project Number on 8­28­18

State of North Carolina
Department of Environment and Natural Resources
Division of Energy, Mineral and Land Resources

STORMWATER MANAGEMENT PERMIT APPLICATION FORM
This form may be photocopied for use as an original
I. GENERAL INFORMATION
1. Project Name (subdivision, facility, or establishment name - should be consistent with project name on plans,
specifications, letters, operation and maintenance agreements, etc.):
Atlantic Coast Pipeline Project
2. Location of Project (street address):
2808 Downing Road
City:Fayetteville County:Cumberland Zip:28312
3. Directions to project (from nearest major intersection):
From I-95, take exit 52 A-B to NC-24 towards Fayetteville/Clinton. At Exit 52B, head towards
Fayetteville/Fort Bragg/Pope AAF. Continue on NC-24 West. Turn left on Downing Road. CYSPR10-A is
located on the left.

4. Latitude:35 02’ 39.45” N Longitude:78 49’ 24.20” W of the main entrance to the project.

II. PERMIT INFORMATION:
1. a. Specify whether project is (check one): New Modification Renewal w/ Modification†
†Renewals with modifications also requires SWU-102 – Renewal Application Form
b. If this application is being submitted as the result of a modification to an existing permit, list the existing
permit number , its issue date (if known) , and the status of
construction: Not Started Partially Completed* Completed* *provide a designer’s certification
2. Specify the type of project (check one):
Low Density High Density Drains to an Offsite Stormwater System Other
3. If this application is being submitted as the result of a previously returned application or a letter from
DEMLR requesting a state stormwater management permit application, list the stormwater project number,
if assigned, SW61807021 and the previous name of the project, if different than currently
proposed, Atlantic Coast Pipeline Project .
4. a. Additional Project Requirements (check applicable blanks; information on required state permits can be
obtained by contacting the Customer Service Center at 1-877-623-6748):
CAMA Major Sedimentation/Erosion Control: 40.6 ac of Disturbed Area
NPDES Industrial Stormwater 404/401 Permit: Proposed Impacts
b. If any of these permits have already been acquired please provide the Project Name, Project/Permit Number,
issue date and the type of each permit:Atlantic Coast Pipeline/ESC-CUMBE-2018-036/Dec. 5, 2017 - Erosion
and Sediment Control; Atlantic Coast Pipeline/DWR Water Quality Certification #WQC004162/Jan. 26, 2018
- 401 Water Quality Certification
Form SWU-101 Version Oct. 31, 2013 Page 6 of 7 1Updated Consultant Contact Information on 8­28­18
VII. DEED RESTRICTIONS AND PROTECTIVE COVENANTS
For all subdivisions, outparcels, and future development, the appropriate property restrictions and protective
covenants are required to be recorded prior to the sale of any lot. If lot sizes vary significantly or the proposed
BUA allocations vary, a table listing each lot number, lot size, and the allowable built -upon area must be
provided as an attachment to the completed and notarized deed restriction form. The appropriate deed
restrictions and protective covenants forms can be downloaded from http://portal.ncdenr.org/web/lr/state-
stormwater-forms_docs. Download the latest versions for each submittal.
In the instances where the applicant is different than the property owner, it is the responsibility of the property
owner to sign the deed restrictions and protective covenants form while the applicant is re sponsible for ensuring
that the deed restrictions are recorded.
By the notarized signature(s) below, the permit holder(s) certify that the recorded property restrictions and
protective covenants for this project, if required, shall include all the items re quired in the permit and listed
on the forms available on the website, that the covenants will be binding on all parties and persons claiming
under them, that they will run with the land, that the required covenants cannot be changed or deleted
without concurrence from the NC DEMLR, and that they will be recorded prior to the sale of any lot.

VIII. CONSULTANT INFORMATION AND AUTHORIZATION1
Applicant: Complete this section if you wish to designate authority to another individual and/or firm (such as a
consulting engineer and/or firm) so that they may provide information on your behalf for this project (such as
addressing requests for additional information).
Consulting Engineer:Christopher J. L. Stahl, P.E.
Consulting Firm: S&ME
Mailing Address:9751 Southern Pine Blvd.
City:Charlotte State:NC Zip:28273
Phone: (704 ) 523-4726 Fax: ( )
Email:[e-mail]

IX. PROPERTY OWNER AUTHORIZATION (if Contact Information, item 2 has been filled out, complete this
section)
I, (print or type name of person listed in Contact Information, item 2a) Martha L. Hair & Kathy Nell Hair Radcliff; John S.
Hair, Jr. , certify that I own the property identified in this permit
application, and thus give permission to (print or type name of person listed in Contact Information, item 1a) Leslie
Hartz with (print or type name of organization listed in
Contact Information, item 1a) Atlantic Coast Pipeline, LLC to develop the project as currently proposed. A copy of
the lease agreement or pending property sales contract has been provided with the submittal, which indicates the
party responsible for the operation and maintenance of the stormwater system.

ATTACHMENT 4

Stormwater Wetland BMP Supplement Forms

STORMWATER WETLAND
1
Drainage area number 221S
Total coastal wetlands area (sq ft)0 sf - Parking / driveway (sq ft)533095 sf
Total surface water area (sq ft)0 sf - Sidewalk (sq ft)0 sf
Total drainage area (sq ft)1193196 sf - Roof (sq ft)0 sf
BUA associated with existing development (sq ft)0 sf - Roadway (sq ft)12973 sf
Proposed new BUA (sq ft)546068 sf - Other, please specify in the comment box below (sq ft) 0 sf
Percent BUA of drainage area 46%Total BUA (sq ft)546068 sf
Design rainfall depth (in)1.0 in
Minimum volume required (cu ft)12310 cf
Design volume of SCM (cu ft)15294 cf
#1 Is the SCM sized to treat the SW from all surfaces at build-out?Yes #7 If applicable, with the SCM be cleaned out after construction?Yes
#2 Is the SCM located on or near contaminated soils?No #8 Does the mainetenance access comply with General MDC (8)?Yes
#3 What are the side slopes of the SCM (H:V)?3:1 #9 Does the drainage easement comply with General MDC (9)?Yes
#3 Does the SCM have retaining walls, gabion walls or other engineered side slopes? No #10 If the SCM is on a single family lot, does the plat comply with General MDC (10)?No
#4 Are the inlets, outlets, and receiving stream protected from erosion (10-year storm)?Yes #11 Is there an O&M Agreement that complies with General MDC (11)?Yes
#5 Is there a a bypass for flows in excess of the design flow?Yes #12 Is there an O&M Plan that complies with General MDC (12)?Yes
#6 What is the method for dewatering the SCM for maintenance?Pump (preferred)#13 Was the SCM designed by an NC licensed professional?Yes
#1 Permanent pool elevation (fmsl)91.75 ft #8 Total surface area of the shallow water zone at temporary pool (square feet)13385 sf
#1 Temporary pool elevation (fmsl)92.25 ft #8 SW wetland surface area comprised of shallow water zone at temporary pool (%)42%
#1 Ponding depth (inches)6 in #8 Depth of the shallow water zone below permanent pool (inches)6 in
#2 Is the SW wetland designed for peak attenuation?No #8 Elevation of bottom of the shallow water zone (fmsl)91.25 ft
#2 If so, peak attenuation depth (inches)-#9 Total surface area of the temporary inundation zone at temporary pool (square feet)12165 sf
#3 Surface area of SW wetland at temporary pool (square feet)32007 sf #9 SW wetland surface area comprised of temp inundation zone at temp pool (%)38%
#4 Depth of soil amendment (inches)0 #9 Height of the temporary inundation zone above permanent pool (inches)6 in
#4 Describe how the soil is being amended to promote plant growth:#9 Elevation of bottom of the temporary inundation zone (fmsl)91.75 ft
#10 Drawdown time for the temporary pool (hours)105 hrs
#10 Does the orifice drawdown from below the top surface of the permanent pool?Yes
#11 Does the pond minimize impacts to the receiving channel from the 1-yr, 24-hr storm?Yes
#6 Are the inlet(s) and outlet located in a manner that avoids short-circuiting?Yes #12 Has a landscaping plan that meets SW Wetland MDC (12) been provided?Yes
#13 Number of plants per 200 square feet (#) in the shallow water zone:50
#6 Surface area of the forebay at temporary pool (square feet)4143 sf
#6 Overall SW wetland surface area comprised of forebay at temporary pool (%)13%
#6 Depth of forebay below permanent pool (inches)24 in #14 Does planting for the temporary inundation zone comply with SW Wetland MDC (14)?Yes
#6 Elevation of bottom of forebay (fmsl)89.75 ft #14 Describe the planting plan for the temporary inundation zone:
#6 Will the forebay be cleaned out when depth is reduced to 15 inches or less?Yes
#7 Total surface area of the non-forebay deep pools at temporary pool (square feet)2314 sf
#7 SW wetland surface area comprised of non-forebay deep pools at temporary pool (%)7%#15 Are the dam structure and temporary fill slopes planted in non-clumping turfgrass?Yes
#7 Depth of non-forebay deep pools below permanent pool (inches)18 in #16 Will cattails be planted in the wetland?No
#7 Elevation of bottom of non-forebay deep pools (fmsl)90.25 ft #17 Is a trash rack or other device provided to protect the outlet system?Yes
ACP - Cumberland Contractor Yard (CY-10A)
In the temporary inundation zone, the plants Bushy Bluestem, Soft Rush, and Wool Grass shall be planted with a
minimum of one plant every 4 square feet.
ADDITIONAL INFORMATION
Please use this space to provide any information about this stormwater wetland that you think is relevant to the review:
The stormwater wetland will be created by modifying the sediment basin that was used during construction. The sediment basin's rock dam and a earthen berm in front of it will be used to establish a temporary pool by allowing water
above 92.25' to flow over the earthen berm and drain through the rock dam.
THE DRAINAGE AREA
STORMWATER WETLAND MDC FROM 02H .1054
The soil is not being amended to promote plant growth. It was not deemed necessary considering the land's past use
for crops.
#6 Describe any measures, such as berms or baffles, that will be taken to improve the flow path:
#13 Describe the planting plan for the shallow water zone:
In the shallow water zone, the plants Arrow Arum, Broadleaf Arrowhead, and Lizard's Tail shall be planted with a
minimum of one plant every 4 square feet.
GENERAL MDC FROM 02H .1050
Break down of BUA in the drainage area (both new and existing):
COMPLIANCE WITH THE APPLICABLE STORMWATER PROGRAM
Stormwater program(s) that apply (please specify):
Phase II
Wetland 1 12:29 PM 9/11/2018
STORMWATER WETLAND ACP - Cumberland Contractor Yard (CY-10A)
2
Drainage area number 222S
Total coastal wetlands area (sq ft)0 sf - Parking / driveway (sq ft)256133 sf
Total surface water area (sq ft)0 sf - Sidewalk (sq ft)0 sf
Total drainage area (sq ft)313435 sf - Roof (sq ft)0 sf
BUA associated with existing development (sq ft)0 sf - Roadway (sq ft)0 sf
Proposed new BUA (sq ft)256133 sf - Other, please specify in the comment box below (sq ft) 0 sf
Percent BUA of drainage area 82%Total BUA (sq ft)256133 sf
Design rainfall depth (in)1.0 in
Minimum volume required (cu ft)8025 cf
Design volume of SCM (cu ft)8640 cf
#1 Is the SCM sized to treat the SW from all surfaces at build-out?Yes #7 If applicable, with the SCM be cleaned out after construction?Yes
#2 Is the SCM located on or near contaminated soils?No #8 Does the mainetenance access comply with General MDC (8)?Yes
#3 What are the side slopes of the SCM (H:V)?3:1 #9 Does the drainage easement comply with General MDC (9)?Yes
#3 Does the SCM have retaining walls, gabion walls or other engineered side slopes? No #10 If the SCM is on a single family lot, does the plat comply with General MDC (10)?No
#4 Are the inlets, outlets, and receiving stream protected from erosion (10-year storm)?Yes #11 Is there an O&M Agreement that complies with General MDC (11)?Yes
#5 Is there a a bypass for flows in excess of the design flow?Yes #12 Is there an O&M Plan that complies with General MDC (12)?Yes
#6 What is the method for dewatering the SCM for maintenance?Pump (preferred)#13 Was the SCM designed by an NC licensed professional?Yes
#1 Permanent pool elevation (fmsl)91.75 ft #8 Total surface area of the shallow water zone at temporary pool (square feet)4608 sf
#1 Temporary pool elevation (fmsl)92.50 ft #8 SW wetland surface area comprised of shallow water zone at temporary pool (%)40%
#1 Ponding depth (inches)9 in #8 Depth of the shallow water zone below permanent pool (inches)6 in
#2 Is the SW wetland designed for peak attenuation?No #8 Elevation of bottom of the shallow water zone (fmsl)91.25 ft
#2 If so, peak attenuation depth (inches)-#9 Total surface area of the temporary inundation zone at temporary pool (square feet)4288 sf
#3 Surface area of SW wetland at temporary pool (square feet)11458 sf #9 SW wetland surface area comprised of temp inundation zone at temp pool (%)37%
#4 Depth of soil amendment (inches)0 #9 Height of the temporary inundation zone above permanent pool (inches)9 in
#4 Describe how the soil is being amended to promote plant growth:#9 Elevation of bottom of the temporary inundation zone (fmsl)91.75 ft
#10 Drawdown time for the temporary pool (hours)55 hrs
#10 Does the orifice drawdown from below the top surface of the permanent pool?Yes
#11 Does the pond minimize impacts to the receiving channel from the 1-yr, 24-hr storm?Yes
#6 Are the inlet(s) and outlet located in a manner that avoids short-circuiting?Yes #12 Has a landscaping plan that meets SW Wetland MDC (12) been provided?Yes
#13 Number of plants per 200 square feet (#) in the shallow water zone:50
#6 Surface area of the forebay at temporary pool (square feet)1396 sf
#6 Overall SW wetland surface area comprised of forebay at temporary pool (%)12%
#6 Depth of forebay below permanent pool (inches)24 in #14 Does planting for the temporary inundation zone comply with SW Wetland MDC (14)?Yes
#6 Elevation of bottom of forebay (fmsl)89.75 ft #14 Describe the planting plan for the temporary inundation zone:
#6 Will the forebay be cleaned out when depth is reduced to 15 inches or less?Yes
#7 Total surface area of the non-forebay deep pools at temporary pool (square feet)1177 sf
#7 SW wetland surface area comprised of non-forebay deep pools at temporary pool (%)10%#15 Are the dam structure and temporary fill slopes planted in non-clumping turfgrass?Yes
#7 Depth of non-forebay deep pools below permanent pool (inches)18 in #16 Will cattails be planted in the wetland?No
#7 Elevation of bottom of non-forebay deep pools (fmsl)90.25 ft #17 Is a trash rack or other device provided to protect the outlet system?Yes
ADDITIONAL INFORMATION
Please use this space to provide any information about this stormwater wetland that you think is relevant to the review:
The stormwater wetland will be created by modifying the sediment basin that was used during construction. The sediment basin's rock dam and a earthen berm in front of it will be used to establish a temporary pool by allowing water
above 92.5' to flow over the earthen berm and drain through the rock dam.
GENERAL MDC FROM 02H .1050
STORMWATER WETLAND MDC FROM 02H .1054
The soil is not being amended to promote plant growth. It was not deemed necessary considering the land's past use
for crops.
#6 Describe any measures, such as berms or baffles, that will be taken to improve the flow path:
#13 Describe the planting plan for the shallow water zone:
In the shallow water zone, the plants Arrow Arum, Broadleaf Arrowhead, and Lizard's Tail shall be planted with a
minimum of one plant every 4 square feet.
Break down of BUA in the drainage area (both new and existing):
COMPLIANCE WITH THE APPLICABLE STORMWATER PROGRAM
Stormwater program(s) that apply (please specify):
Phase II
In the temporary inundation zone, the plants Bushy Bluestem, Soft Rush, and Wool Grass shall be planted with a
minimum of one plant every 4 square feet.
THE DRAINAGE AREA
Wetland 1 12:31 PM 9/11/2018

ATTACHMENT 5

Stormwater Wetland O&M Agreements and Plans

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After the stormwater wetland is established, it shall be inspected monthly and within 24 hours after every storm event greater
than 1.0 inches (or 1.5 inches if in a Coastal County). Records of operation and maintenance will be kept in a known set
location and will be available upon request.
Inspection activities shall be performed as follows. Any problems that are found shall be repaired immediately.
Vegetation is too short or too
long.
Maintain vegetation at a height of approximately six inches.
Stormwater Wetland Maintenance Requirements
Once a year, a dam safety expert should inspect the embankment.
Forebay Sediment has accumulated in
the forebay to a depth that
inhibits the forebay from
functioning well.
Search for the source of the sediment and remedy the problem if
possible. Remove the sediment and dispose of it in a location where it
will not cause impacts to streams or the BMP.
Remove the weeds, preferably by hand. If a pesticide is used, wipe it
on the plants rather than spraying.
BMP element:Potential problem:How I will remediate the problem:
The perimeter of the BMP Areas of bare soil and/or
erosive gullies have formed.
Regrade the soil if necessary to remove the gully, and then plant a
ground cover and water until it is established. Provide lime and a one-
time fertilizer application.
Entire BMP Trash/debris is present.Remove the trash/debris.
Remove sediment and replace with clean stone.
Erosion has occurred.Provide additional erosion protection such as reinforced turf matting or
riprap if needed to prevent future erosion problems.
Weeds are present.
The inlet device The pipe is clogged.
Erosion is occurring in the
swale.
Regrade the swale if necessary to smooth it over and provide erosion
control devices such as reinforced turf matting or riprap to avoid future
problems with erosion.
Stone verge is clogged or
covered in sediment (if
applicable).
Unclog the pipe. Dispose of the sediment off-site.
The pipe is cracked or
otherwise damaged.
Replace the pipe.
Important maintenance procedures:
Stable groundcover will be maintained in the drainage area to reduce the sediment load to the wetland.
Immediately following construction of the stormwater wetland, bi-weekly inspections will be conducted and
wetland plants will be watered bi-weekly until vegetation becomes established (commonly six weeks).
No portion of the stormwater wetland will be fertilized after the first initial fertilization that is required to establish
the wetland plants.
STORM-EZ
Version 1.4 O&M Manual
8/31/2018
Page 3 of 4
Stormwater Wetland Maintenance Requirements (Continued)
Deep pool, shallow water
and shallow land areas
Algal growth covers over 50%
of the deep pool and shallow
water areas.
Consult a professional to remove and control the algal growth.
Cattails, phragmites or other
invasive plants cover 50% of
the deep pool and shallow
water areas.
Remove invasives by physical removal or by wiping them with
pesticide (do not spray) – consult a professional.
Shallow land remains flooded
more than 5 days after a
storm event.
Unclog the outlet device immediately.
Plants are dead, diseased or
dying.
Determine the source of the problem: soils, hydrology, disease, etc.
Remedy the problem and replace plants. Provide a one-time fertilizer
application to establish the ground cover if necessary.
The outlet device is damaged Repair or replace the outlet device.
Clogging has occurred.Clean out the outlet device. Dispose of the sediment off-site.
Embankment
Prune according to best professional practices.
Sediment has accumulated
and reduced the depth to 75%
of the original design depth of
the deep pools.
Search for the source of the sediment and remedy the problem if
possible. Remove the sediment and dispose of it in a location where it
will not cause impacts to streams or the BMP.
Best professional practices
show that pruning is needed
to maintain optimal plant
health.
Evidence of muskrat or
beaver activity is present.
Make all needed repairs.
A tree has started to grow on
the embankment.
Consult a dam safety specialist to remove the tree.
An annual inspection by
appropriate professional
shows that the embankment
needs repair.Consult a professional to remove muskrats or beavers.
Sediment has accumulated
and reduced the depth to 75%
of the original design depth.
Search for the source of the sediment and remedy the problem if
possible. Remove the sediment and dispose of it in a location where it
will not cause impacts to streams or the BMP.
The outlet device
Micropool
The receiving water Erosion or other signs of
damage have occurred at the
outlet.
Contact the local NC Department of Environment and Natural
Resources Regional Office.
STORM-EZ
Version 1.4 O&M Manual
8/31/2018
Page 4 of 4

ATTACHMENT 6

Property Deeds

ATTACHMENT 7

Soils Report by S&EC
Geosyntec Consultants of NC, PC March 30, 2018
Attn: Mr. Beau Hodge, P.G. (NC) Principal S&EC Project # 13479.S1
2501 Blue Ridge Road, Suite 430
Raleigh, NC 27607
Re: Soil Evaluation and In-Situ Conductivity Measurements – Contractor Yard Site, Cumberland
County, NC.
Dear Mr. Hodge:
Soil & Environmental Consultants, PA (S&EC) S&EC was contacted to help assess the soil conditions
within the vicinity of the potential storm water BMP sites on the project mentioned above. The
purpose of this evaluation was to provide soil data for the proper design of the potential storm water
BMP, including the depth to the seasonal high water table (SHWT) and the in-situ testing of the
unsaturated soil horizons at the contractor yard site in Cumberland County, NC. This report discusses
S&EC’s methods and testing results and was completed as per our scope of work dated March 25,
2018.
Soil/Site Evaluation Methodology
The site evaluation was performed by advancing a hand auger to complete the soil borings to a depth
of 4 feet within the proposed storm water BMP areas (see attached Figure 1 Map). The soil boring
locations were determined by the client prior to S&EC’s field evaluation. Soil morphological
conditions using standard techniques outlined in the “Field Book for Describing and Sampling Soils,
Version 3” published by the Natural Resources Conservation Service (NRCS, 2012). A detailed soil
profile description from each of the soil boring locations (Site 1 thru Site 4) are included in Attachment
1 to this report.
Soil/Site Conditions
This site is located in the middle coastal plain region of Cumberland County, NC. The sites shown on
the attached map are in an open agricultural field. These soils range from somewhat poorly drained to
poorly drained soils with moderate to slow permeable infiltration rates. Within the in-situ testing phase
of this evaluation (described below), S&EC was able to test the conductivity rate at the targeted depth
of 12 inches below land surface at two locations, at 6 inches at one location and due to saturated soil
conditions, one site was unable to be tested.
At the first area evaluated (Site 1), S&EC did observed a seasonal high water table within 13 inches
below top of ground. The apparent water table (free water in the borehole) was noted at 44 inches
below the top of ground. At this location, the upper 10 inches was a sandy loam soil and the lower
portion was sandy clay loam. See the soil profile description (Site 1) in Attachment 1 below.
Within the second BMP area (Site 2), S&EC observed a seasonal high water table within 23 inches
below top of ground. There was not an apparent water table observe within 48 inches below the top of
ground. At this location, the upper 23 inches was a sandy loam soil and the lower portion was sandy
clay loam. See the soil profile description (Site 2) in Attachment 1 below.

Within the third BMP area (Site 3), S&EC did observed a seasonal high water table at the land surface
as this soil is identified as poorly drained. The apparent water table (free water in the borehole) was
observed at 20 inches below the top of ground and the soil was noted as saturated at field capacity.
Also in areas near the boring site, the land surface was noted as being saturated. At this location, the
upper 11 inches was a clay loam soil and the lower portion was clay. See the soil profile description
(Site 3) in Attachment 1 below. Due to these conditions, we were unable to conduct an in-situ
measurement at this location.

At the fourth area evaluated (Site 4), S&EC did observed a seasonal high water table within 5 inches
below top of ground. The apparent water table (free water in the borehole) was not observed within 36
inches below the top of ground. At this location, the upper 5 inches was a sandy loam soil and the
lower portion was clay loam to sandy clay loam. See the soil profile description (Site 4) in Attachment
1 below. Given the soil moisture conditions and depth to the seasonal high water table, we conducted
an in-situ test measurement at 6 inches below top of ground at this location.

Given the site topography and sloping conditions within the agricultural field, the seasonal high water
table could vary across the BMP areas and the soil boring descriptions (noted below) were a single
targeted point within the BMP’s. If needed, S&EC can conduct additional soil borings and testing in
the area.

In-Situ Hydraulic Conductivity Analysis:

In-situ saturated hydraulic conductivity (Ksat) measurements were conducted in the unsaturated soil
horizons at three sites within the target BMP areas by the constant head well permeameter technique
(also known as shallow well pump-in technique and bore hole permeameter method). These sites are
shown on the attached map (Site 1, Site 2 & Site 4). The initial target depth to run this in-situ analysis
was 12 inches below land surface at each location, however as mentioned above Site 4 was ran at 6
inches below top of land surface. This in-situ Ksat procedure is described in Methods of Soil Analysis,
Part 1., Chapter 29 – Hydraulic Conductivity of Saturated Soils: Field Methods, 29 – 3.2 Shallow
Well Pump In Method, pp. 758-763 and in the Soil Science Society of America Journal, Vol. 53, no. 5,
Sept. – Oct. 1989, “A Constant-head Permeameter for Measuring Saturated Hydraulic Conductivity of
the Vadose Zone” and “Comparison of the Glover Solution with the Simultaneous – Equations
Approach for Measuring Hydraulic Conductivity.” In essence, a volume of water was applied and
measured with time until a steady state of water flow was achieved. This volume/time with steady
state was used to calculate the saturated hydraulic conductivity of the subsoil by the Glover equation.

The Ksat value for each site is summarized below. Ksat data calculations are provided in Attachment
2 of this report.

Ksat Location Horizon, Soil Texture & Testing Depth Ksat Values (in/hr)
Site 1
A & Upper Bt, Sandy Loam & Sandy Clay
Loam, 12 inches 0.10
Site 2 A, Sandy Loam, 12 inches 0.32
Site 4
A & Upper Bt, Sandy Loam & Clay loam,
6 inches 0.11

These measurements were made in the unsaturated soil zone and are not intended to provide values of
the saturated zone, possible mounding or the rate of water movement off site. The hydraulic
conductivity of soil varies based on the soil texture and conditions. The test results noted above
should be used as a general guide in the decision of the final construction and permitting of the storm
water device, however any soil variations or site impacts within the BMP could affect the results.

Attachment 1.
Soil Boring Profile Descriptions

SITE-1

Horizon &
Depth
Texture, &
Structure
Munsell Color Notes
A
0 – 4 in
Sandy Loam, Granular 10 YR 2/2

BE
4 – 10 in
Sandy Loam, Granular 10 YR 6/4 Not Sticky, Not
Plastic

Bt1
10 – 13 in
Sandy Clay Loam, Medium,
Subangular Blocky
10 YR 5/3 Slightly Sticky,
Slightly Plastic

Bt2
13 – 22 in
Sandy Clay Loam,
Massive, Medium,
Subangular Blocky
10 YR 5/3
7.5 YR 5/3
Sticky, Plastic
Bt3
22 – 32 in
Sandy Clay Loam, Massive,
Medium, Subangular
Blocky
10 YR 6/2
7.5 YR 5/6
Dual Matrix
Colors, Sticky,
Plastic

C
32 – 48 in
Sandy Loam/Sandy Clay
Loam
10 YR 6/1
7.5 YR 5/6
Patches of gley
clay

Seasonal High
Water Table
Indicators observed
within 13 inches
below land surface

Apparent Water
Table Observed
within 44 inches of
land surface

SITE-2
Horizon &
Depth
Texture, &
Structure
Munsell Color Notes
A
0 – 5 in
Sandy Loam,
Weak, Medium, Granular
10 YR 3/2
E
5 – 13 in
Sandy Loam,
Weak, Medium, Granular
2.5 Y 4/4
BE
13 – 23 in
Sandy Loam, Weak,
Medium, Subangular
Blocky
10 YR 6/1
Bt1
23 – 32 in
Sandy Clay Loam,
Weak, Medium, Subangular
Blocky
10 YR 6/8
7.5 YR 5/8
10 YR 6/1
Mottled, Slightly
Sticky, Slightly
Plastic
Bt2
35 – 41 in
Sandy Clay Loam,
Moderate, Medium,
Subangular Blocky
10 YR 6/1
7.5 YR 5/6
Sticky, Plastic
Btg
41 – 48 in
Sandy Clay Loam,
Moderate, Medium,
Subangular Blocky
10 YR 6/1
7.5 YR 5/6
Sticky, Plastic
Seasonal High
Water Table
Indicators observed
within 23 inches
below land surface
No Apparent
Water Table
Observed within 4
feet of land surface

SITE-3

Horizon &
Depth
Texture, &
Structure
Munsell Color Notes
A/B
0 – 11 in
Clay Loam, Weak, Medium,
Subangular Blocky
10 YR 3/1
7.5 YR 5/2
10 YR 4/6
Slightly Sticky,
Slightly Plastic

Bt
11 – 20 in
Clay, Moderate, Medium,
Subangular Blocky
10 YR 4/2
7.5 YR 5/2
10 YR 4/1
Sticky, Plastic
Btg1
20 – 29 in
Clay, Moderate to Strong,
Medium, Subangular
Blocky
10 YR 5/2
7.5 YR 5/2
10 YR 4/1
Sticky, Plastic
Btg2
29 – 36 in
Clay, Strong, Medium,
Subangular Blocky
10 YR 5/1
7.5 YR 5/2
10 YR 4/1
Very Sticky, Very
Plastic

Seasonal High
Water Table
Indicators observed
at surface, standing
water observed
near site

Apparent Water
Table observed
within 20 inches of
land surface

SITE-4
Horizon &
Depth
Texture, &
Structure
Munsell Color Notes
Ap
0 – 5 in
Sandy Loam, Weak,
Medium,
Subangular Blocky
10 YR 3/2 Not Sticky, Not
Plastic
Bt1
5 – 16 in
Clay Loam, Medium,
Moderate, Subangular
Blocky
7.5 YR 5/6
7.5 YR 5/2
Slightly Sticky,
Slightly Plastic
Bt2
16 – 26 in
Clay, Moderate, Medium,
Subangular Blocky
7.5 YR 5/6
7.5 YR 5/2
7.5 YR 5/1
Sticky, Plastic
BCg
26 – 34 in
Sandy Clay Loam, Strong,
Medium, Subangular
Blocky
7.5 YR 6/1
7.5 YR 6/6
Sticky, Plastic
Cg
34+ in
Sandy Loam, Structureless 7.5 YR 6/1
7.5 YR 6.6
Very Friable, Not
Sticky, Not Plastic
Seasonal High
Water Table
Indicators observed
at 5 inches
No Apparent Water
Table observed
within 36 inches

Attachment 2
In-Situ Ksat Worksheets

Calculating Saturated Hydraulic Conductiviy, Ksat, by the Glover model
INFORMATION
Date 3/29/2018
Measurement Conducted By Don Wells
Job Name Cumberland Yard BMP's
Job Number 13479.S1
Weather Cond., Temp.sunny, 72
Ksat Location Site # 1
Soil Ag Field
Horizon A & Bt, SL & SCL
Source of Water tap
Required Data Value Units
Radius of Hole 2.5 cm
Depth of Hole 30.48 cm
Initial Depth of Water in Hole (H)22.86 cm
Final Depth of Water in Hole (H)22.86 cm
Start Saturation Time 12:13 Hour:Min
Start of Steady-State Condition Time 13:01 Hour:Min
No. of Reservoirs Used at Steady-State 2
Ratio H/r 9.1440
A factor in Equation [2] of Manual 0.000613
Clock Water Time Change Flow Flow Flow
Time Level Interval in Water Volume Rate Rate
Reading Level Q Q Ksat Ksat
Hr.Min cm Minute cm cm3 cm3/min cm3/hour cm/hour cm/day
cm/hour in/hour gpd/sf
12.13 19.5 0.26 0.10 1.54
12.16 13.3 3.00 6.2 651 217.00 13020.0 7.98 191.54
12.31 12.4 15.00 0.9 94.5 6.30 378.0 0.23 5.56
13.01 10.2 30.00 2.2 231 7.70 462.0 0.28 6.80
13.31 8 30.00 2.2 231 7.70 462.0 0.28 6.80
14.01 6.1 30.00 1.9 199.5 6.65 399.0 0.24 5.87
14.31 4 30.00 2.1 220.5 7.35 441.0 0.27 6.49
14.46 3 15.00 1 105 7.00 420.0 0.26 6.18
15.01 2 15.00 1 105 7.00 420.0 0.26 6.18 inch cm
15.16 1 15.00 1 105 7.00 420.0 0.26 6.18 Hole Depth:12 30.48
Hi:9 22.86
Hf:9 22.86
Graph Data
Time Ksat
12.31 0.23
13.01 0.28
13.31 0.28
14.01 0.24
14.31 0.27
14.46 0.26
15.01 0.26
15.16 0.26
AVERAGE:
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
10.00 11.00 12.00 13.00 14.00 15.00 16.00
Series1
Calculating Saturated Hydraulic Conductiviy, Ksat, by the Glover model
INFORMATION
Date 3/29/2018
Measurement Conducted By Don Wells
Job Name Cumberland Yard BMP's
Job Number 13479.S1
Weather Cond., Temp.sunny, 70
Ksat Location Site # 2
Soil Ag Field
Horizon A, Sandy loam
Source of Water tap
Required Data Value Units
Radius of Hole 2.5 cm
Depth of Hole 30.48 cm
Initial Depth of Water in Hole (H)15.24 cm
Final Depth of Water in Hole (H)15.24 cm
Start Saturation Time 12:06 Hour:Min
Start of Steady-State Condition Time 12:36 Hour:Min
No. of Reservoirs Used at Steady-State 2
Ratio H/r 6.0960
A factor in Equation [2] of Manual 0.001136
Clock Water Time Change Flow Flow Flow
Time Level Interval in Water Volume Rate Rate
Reading Level Q Q Ksat Ksat
Hr.Min cm Minute cm cm3 cm3/min cm3/hour cm/hour cm/day
12.06 26
12.21 20.8 15.00 5.2 546 36.40 2184.0 2.48 59.56
12.36 19.2 15.00 1.6 168 11.20 672.0 0.76 18.33
13.06 16.1 30.00 3.1 325.5 10.85 651.0 0.74 17.75 cm/hour in/hour gpd/sf
13.36 13 30.00 3.1 325.5 10.85 651.0 0.74 17.75 0.81 0.32 4.80
14.06 9.6 30.00 3.4 357 11.90 714.0 0.81 19.47
14.36 6.4 30.00 3.2 336 11.20 672.0 0.76 18.33
15.06 2.6 30.00 3.8 399 13.30 798.0 0.91 21.76
15.21 1 15.00 1.6 168 11.20 672.0 0.76 18.33
inch cm
Hole Depth:12 30.48
Hi:6 15.24
Hf:6 15.24
Graph Data
Time Ksat
12.36 0.76
13.06 0.74
13.36 0.74
14.06 0.81
14.36 0.76
15.06 0.91
15.21 0.76
AVERAGE:
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
10.00 11.00 12.00 13.00 14.00 15.00 16.00
Series1
Calculating Saturated Hydraulic Conductiviy, Ksat, by the Glover model
INFORMATION
Date 3/29/2018
Measurement Conducted By Don Wells
Job Name Cumberland Yard BMP's
Job Number 13479.S1
Weather Cond., Temp.sunny, 72
Ksat Location Site #4
Soil Ag Field
Horizon A & Bt; SL & CL
Source of Water tap
Required Data Value Units
Radius of Hole 2.5 cm
Depth of Hole 15.24 cm
Initial Depth of Water in Hole (H)15.24 cm
Final Depth of Water in Hole (H)15.24 cm
Start Saturation Time 11:48 Hour:Min
Start of Steady-State Condition Time 12:20 Hour:Min
No. of Reservoirs Used at Steady-State 2
Ratio H/r 6.0960
A factor in Equation [2] of Manual 0.001136
Clock Water Time Change Flow Flow Flow
Time Level Interval in Water Volume Rate Rate
Reading Level Q Q Ksat Ksat
Hr.Min cm Minute cm cm3 cm3/min cm3/hour cm/hour cm/day
cm/hour in/hour gpd/sf
0.27 0.11 1.62
11.48 11.8
11.50 9.2 2.00 2.6 273 136.50 8190.0 9.31 223.34
12.20 7.1 30.00 2.1 220.5 7.35 441.0 0.50 12.03
12.50 5.6 30.00 1.5 157.5 5.25 315.0 0.36 8.59
13.20 4.1 30.00 1.5 157.5 5.25 315.0 0.36 8.59
13.50 3 30.00 1.1 115.5 3.85 231.0 0.26 6.30
14.20 2 30.00 1 105 3.50 210.0 0.24 5.73 inch cm
14.50 1 30.00 1 105 3.50 210.0 0.24 5.73 Hole Depth:6 15.24
Hi:6 15.24
Hf:6 15.24
Graph Data
Time Ksat
12.20 0.50
12.50 0.36
13.20 0.36
13.50 0.26
14.20 0.24
14.50 0.24
AVERAGE:
0.00
0.10
0.20
0.30
0.40
0.50
0.60
12.00 12.50 13.00 13.50 14.00 14.50 15.00
Series1
@?
@?
@?
@?-78.822244, 35.042356
-78.824596, 35.045426
-78.823073, 35.046019
-78.820309, 35.042148
NC HWY 24
DOWNING RD
ACCORD RDNC Center for Geographic Information & Anaylsis
Project Number:
DWProject Manager:
1" = 300'Scale:
03/29/18Date:
Map Title:
Source:
Ksat & Soil Boring Map
North Carolina ACP Contractor Yard
Cumberland County, NC
Cumberland Co GIS,
2017 aerial from NCOneMap.com
13479.S1 ­Figure 1
0 150 300 450 600Feet
Legend
@?Ksat & Soil Boring Locations

ATTACHMENT 8

Stormwater Wetlands Calculation Report

NCDEQ Permit Review
Cumberland County ACP CY SPR 10A
Stormwater Wetland Calculation
Dominion Services
S&ME Project No. 7235-17-008

August 30, 2018 1
COMPUTATIONS BY: Signature Date 8-31-18
Name Matthew H. Kunkle, E.I.
Title Staff Professional II

ASSUMPTIONS Signature Date 8-31-18
AND PROCEDURES Name James R. Hubbard, E.I.
CHECKED BY: Title Staff Professional II

COMPUTATIONS Signature Date 8-31-18
CHECKED BY: Name James R. Hubbard, E.I.
Title Staff Professional II

REVIEWED BY: Signature Date 8-31-18
Name Chris J. L. Stahl, P.E.
Title Principal Engineer

REVIEW NOTES / COMMENTS:

NCDEQ Permit Review
Cumberland County ACP CY SPR 10A
Stormwater Wetland Calculation
Dominion Services
S&ME Project No. 7235-17-008

August 30, 2018 2
 OBJECTIVE
The objective of this calculation report is to design the proposed stormwater wetlands in accordance with
the design criteria presented in the North Carolina Department of Environment al Quality (NCDEQ)
Stormwater Design Manual.
 SUMMARY
The proposed stormwater wetlands have been designed in accordance with the minimum design criteria
presented in the NCDEQ Stormwater Design Manual.
 REFERENCES
1. NOAA Atlas 14, Sediment storage volume 2, Version 3, Bonnin, G.M., Martin, D., Lin, B., Parzybok,
T., Yekta, M., & Riley, D., December 5, 2014.
2. Erosion and Sediment Control Planning and Design Manual, Chapter 8.03, NCDEQ, Revised May,
2013.
3. NRCS Web Soil Survey, Cumberland County, Accessed August 21, 2018.
4. HydroCAD Reports, S&ME Inc., August 2018.
5. Watersheds, S&ME Inc., August 2018.
6. Stormwater Design Manual, Part C-0, NCDEQ, Revised January 3, 2017.
7. Stormwater Design Manual, Part C-4, NCDEQ, Revised January 19, 2018.
8. NCDEQ Riprap Lined Plunge Pool for Cantilever Outlet Design, Last revised Jan. 23, 1986.

 DEFINITION OF VARIABLES
Q = flow rate (cfs)
CN = curve number
i = rainfall intensity (in/hr)
A = drainage area (acres)
Tc = time of concentration (min)
Tt = component of time of concentration (min)
L = spillway length, length of pipe (ft)
a = cross-sectional area of the pipe (ft2)
g = gravity (ft/s2)
WAB = weight of anti-flotation block
LAB = length of anti-flotation block
HAB = height of anti-flotation block
c = unit weight of concrete
w = unit weight of water
Uriser = uplift force acting on riser
H = height of riser (ft)
Ar = area of riser (ft2)
d = orifice diameter (in)
P2 = 2-year, 24-hour rainfall (in)
NCDEQ Permit Review
Cumberland County ACP CY SPR 10A
Stormwater Wetland Calculation
Dominion Services
S&ME Project No. 7235-17-008

August 30, 2018 3
n = Manning’s roughness coefficient
v= velocity (ft/s)
Do = Outlet Pipe Diameter (ft)
d50 = Riprap Size (ft)
R= hydraulic radius (ft)
S= slope (ft/ft)
d= depth (ft)
 KNOWN AND ASSUMED VARIABLES
g = 32.2 ft/s2 [assumed]
P1 yr, 24 hr = 3.03 in, P2 yr, 24 hr = 3.66 in [Ref. 1, Table P.F., pg. 1]
y = 62.4 lb/ft3 [assumed]
NCDEQ Permit Review
Cumberland County ACP CY SPR 10A
Stormwater Wetland Calculation
Dominion Services
S&ME Project No. 7235-17-008

August 30, 2018 4
 CALCULATIONS FOR POST CONSTRUCTION STORMWATER
WETLANDS
1.1 Determine flow into stormwater wetlands for design storms.
There were two areas of interest for this site. The areas of interest are analysis points of a contributing
watershed or group of sub-catchments for which all limits of disturbance are contained within the same
watershed in order to determine the peak discharges during design storms. AOI-1 is the area adjacent to
the wetland located on the south end of the site. AOI-2 is the area in the northwest of the site where the
drainage ditches adjacent to the roads are located.

Runoff for the design storms was calculated using the Curve Number Method, presented as follows:

[Ref. 2, Section 8.03]

The curve number “CN” is an empirical parameter used within hydrology to predict direct runoff from
rainfall. Drainage areas within the scope of this project consisted of multiple soils with varying covers so a
weighted curve number had to be created for each watershed as shown in Tables 1 and 2. The hydrologic
soil groups for the site were determined using NRCS’s Web Soil Survey (Reference 3). The breakdown of
the combined curve number can be seen in Reference 4, S&ME’s Compiled Hydro -CAD Reports.
Table 2: Proposed Conditions
Curve Number Summary Table
Drainage
Area
Total Area
(acres)
Combined
Curve Number
221S 27.4 85
222S 7.2 94

The time of concentration is the time for flow from the most hydrologically remote point in the
contributing drainage area to leave the watershed. Delineations of watersheds can be found in Reference
5. The time of concentration was estimated using the TR-55 method (Reference 2). The TR-55 method
provides equations to compute the time of concentration by summing all the travel times for consecutive
components of the drainage conveyance system. The first component of the drainage conveyance system
was sheet flow. For sheet flow of less than 100 feet, the following equation was used:

4.05.0
2
8.0007.0
sP
nLTt [Ref. 2]
Table 1: Existing Conditions
Curve Number Summary Table
Drainage
Area
Total Area
(acres)
Combined
Curve Number
121S 24.6 64
122S 4.5 55
123S 3.7 73
124S 3.1 64
NCDEQ Permit Review
Cumberland County ACP CY SPR 10A
Stormwater Wetland Calculation
Dominion Services
S&ME Project No. 7235-17-008

August 30, 2018 5
The estimated sheet flow travel time to each area of interest was calculated, as shown in the following
table:

Table 3: Project Sheet Flow
Location ID
Manning's
Roughness
Coefficient {n}
(Ref. 2)
Length {L}
(ft)
Slope
{s}
(ft/ft)
2-Yr, 24-Hr
Rainfall (in)
[Ref. 1]
Travel Time
{Tt1}
(min)
121S 0.15 100 0.015 3.66 10.3
122S 0.15 100 0.019 3.66 9.4
123S 0.15 100 0.005 3.66 16.0
124S 0.15 100 0.008 3.66 13.2
221S 0.01 100 0.021 3.66 1.1
222S 0.15 100 0.003 3.66 19.6

The second component of the drainage conveyance system was shallow concentrated flow. Shallow
concentrated flow was determined using the following equations:

5.0)(*1345.16 sVunpaved [Ref. 2]

(min)60*V
LTt [Ref. 2]

The estimated shallow concentrated flow travel time to each area of interest was calculated, as shown in
the following table:
Table 4: Project Shallow Concentrated Flow
Location
ID
Surface
Description
Average
Velcity
{V}
(ft/s)
Length {L}
(ft)
Slope
{s}
(ft/ft)
Travel Time
{Tt2}
(min)
121S Short Grass Pasture 7.0 840 0.004 33.3
122S Short Grass Pasture 7.0 287 0.014 5.8
123S Short Grass Pasture 7.0 857 0.003 40.8
124S Short Grass Pasture 7.0 570 0.005 19.2
221S #1 Unpaved 16.1 171 0.004 2.9
221S #2 Short Grass Pasture 7.0 384 0.002 22.9
221S #3 Short Grass Pasture 7.0 118 0.003 5.5
222S Short Grass Pasture 7.0 212 0.003 9.2

NCDEQ Permit Review
Cumberland County ACP CY SPR 10A
Stormwater Wetland Calculation
Dominion Services
S&ME Project No. 7235-17-008

August 30, 2018 6
The third and last component of the drainage conveyance system was open channel flow. Travel times for
open channel flow were determined using the following equations:
n
srV
2/13/2 **49.1 [Ref. 2]

(min)60*V
LTt [Ref. 2]
The estimated open channel flow travel time to each area of interest was calculated, as shown in the
following table:
Table 5: Project Open Channel Flow
Location
ID
Slope
{s}
(ft/ft)
Manning's
Roughness
Coefficient
{n}
Length
{L}
(ft)
Travel
Time {Tt3}
(min)
221S 0.022 0.04 150 0.4
222S 0.003 0.05 875 9.3

Due to water from 221S most hydrologically distant point travelling through two culverts, the travel times
within the culverts were assessed using Hydro-CAD and summarized below. In Table 6, the Manning’s
roughness coefficient used was provided by HydroCAD for the typical value of a corrugated metal pipe.
Table 6: Project Pipe Flow
Location ID
Slope
{s}
(ft/ft)
Manning's
Roughness
Coefficient
{n} (Ref. 2)
Length {L}
(ft)
Diameter
(in)
Travel Time
{Tt4}
(min)
221S Culvert #1 0.008 0.025 24 18 0.2
221S Culvert #2 0.006 0.025 32 18 0.3

NCDEQ Permit Review
Cumberland County ACP CY SPR 10A
Stormwater Wetland Calculation
Dominion Services
S&ME Project No. 7235-17-008

August 30, 2018 7
The time of concentration is computed by summing all the travel times for consecutive components of
the drainage conveyance system and the results are summarized in the table below:
Table 7: Estimated Time of Concentration
Location ID
Sheet Flow
Travel
Time
(min)
[Ref.3]
Shallow
Concentrated
Flow Travel
Time
(min)
[Ref.3]
Channel
Flow Travel
Time
(min)
[Ref.3]
Pipe Flow
Travel
Time (min)
Time of
Concentration
(min)
[Ref.3]
121S 10.3 33.3 0.0 0.0 43.6
122S 9.4 5.8 0.0 0.0 15.2
123S 16.0 40.8 0.0 0.0 56.8
124S 13.2 19.2 0.0 0.0 32.4
221S 1.1 31.3 0.4 0.5 33.3
222S 19.6 9.2 9.3 0.0 38.1

1.2 Determine the required surface area.
The design storm used to calculate the design volume that should be treated by the stormwater wetlands
is a 1 inch storm since Cumberland County is a non-coastal county (Ref. 6, MDC 1). The required minimum
surface area is the surface area for a stormwater wetland that limits the depth of the temporary
inundation zone to a maximum of 15 inches (Ref. 7, MDC 3). Using HydroCAD, the design volumes of a 1
inch storm that enters each stormwater wetland after flowing through the watershed s are listed in Table 8.
From the peak elevation of the 1” storm, the surface area provided from the temporary ponding depth
was found.
Table 8: Stormwater Wetland Surface Area Check
Stormwater
Wetland ID
1" Storm Volume
Post Construction
(cu. ft.)
Area
Required
(sq. ft.)
Area
Provided
(sq. ft.)
Depth from
Area Provided
(in.)
Area Provided
> Area
Required
221S 12,312 9,850 34,443 6 YES
222S 8,197 6,558 24,337 9 YES

1.3 Establish the stormwater drawdown times are within two to five days.
The design volumes calculated in Step 1.2 must be drawn out of the stormwater wetlands between two
and five days (Ref. 7, MDC 10). The table below summarizes S&ME’s HydroCAD calculations (Ref. 4).

Table 9: Stormwater Drawdown Time Check
Stormwater
Wetland ID
Drawdown
Time (hours)
Drawdown
Time (days)
Is Drawdown Time
within 2-5 Days?
221S 108 4.5 YES
222S 58 2.4 YES

NCDEQ Permit Review
Cumberland County ACP CY SPR 10A
Stormwater Wetland Calculation
Dominion Services
S&ME Project No. 7235-17-008

August 30, 2018 8
1.4 Verifying the protection of the receiving stream.
The stormwater wetlands shall discharge the runoff from the one-year, 24-hour storm in a manner that
minimizes hydrologic impacts to the receiving channels (Ref. 7, MDC 11). The table below summarizes
S&ME’s HydroCAD calculations (Ref. 4). Pre-construction 121S and 124S watershed flows have been
added together to compare with the Post-construction 221S watershed flow. Pre-construction 122S and
123S watershed flows have been added together to compare with the Post-construction 222S watershed
flow.
Table 10: Receiving Stream Flow Comparisons
Design Storm
221S AOI 222S AOI
Pre Con
Peak Flow
(cfs)
Post Con Peak
Flow (cfs)
Pre Con Peak
Flow (cfs)
Post Con Peak
Flow (cfs)
1-yr 6.3 5.7 2.0 0.3

1.5 Determine Anti-Flotation Block Size.
The anti-flotation blocks were designed for the stormwater wetland risers such that the weight of the anti-
flotation block (including the riser concrete walls) was at least 10% more than the weight of the water
displaced (or uplift force on the riser), where the weight of the anti-flotation block is:
WAB = LAB2 x HAB x c
And, the weight of the water displaced (or uplift force on the riser) is:
Uriser = [H x Ar x w] + [LAB2 x HAB x w]
The anti-flotation block sizing was designed as shown in the table below:
Table 11: Anti-Flotation Block Design
Stormwater
Wetland ID
Bottom
of Riser
Elevation
(ft)
Top of
Riser
Elevation
(ft)
Riser
Height
{H}
(ft)
Riser/Anti-
Flotation
Block
Area
{Ar}
(ft2)
Uplift
Force
on Riser
{Uriser}
(lb)
Height of
Anti-Flotation
Block
{HAB}
(ft)
Weight of
Anti-Flotation
Block {WAB}
(lb)
Safety
Factor
Against
Uplift
221S 91.5 94.5 3.0 12.00 2,621 0.50 3,600 1.37
222S 91.5 94.5 3.0 12.00 2,621 0.50 3,600 1.37

For construction purposes, this anti-floatation block is equivalent to a 2’ x 3’ precast concrete riser with a
6” thick concrete floor.
NCDEQ Permit Review
Cumberland County ACP CY SPR 10A
Stormwater Wetland Calculation
Dominion Services
S&ME Project No. 7235-17-008

August 30, 2018 9
1.6 Determine Anti-Seep Collar Size.
An anti-seep collar will be installed along the culvert pipe downstream of the stormwater wetland. The
anti-seep collar size was calculated to project at least 1.5 feet from the culvert pipe as shown in the
following table:
Table 12: Anti-Seep Collar Design
Stormwater
Wetland ID
Outlet Pipe
Diameter
(in)
Anti-Seep
Collar Size
(ft)
221S 6 4
222S 6 4

1.7 Soil Amendments.
The existing soil condition is conducive to plant growth so no soil amendments are deemed necessary.
Area has been previously used for agricultural purposes.
1.8 Riprap Plunge Pool Design.
The riprap plunge pool designs seen in the drawing set were created using NCDEQ’s “Riprap Lined Plunge
Pool for Cantilever Outlet” excel spreadsheet (Ref. 8). These designs satisfy all technical requirements.

 DISCUSSION
The proposed stormwater wetlands have been designed in accordance with the minimum design criteria
presented in the NCDEQ Stormwater Design Manual.

REFERENCES

REFERENCE 1

NOAA Atlas 14, Sediment storage volume 2, Version 3, Bonnin, G.M.,
Martin, D., Lin, B., Parzybok, T., Yekta, M., & Riley, D., December 5,
2014.
NOAA Atlas 14, Volume 2, Version 3
Location name: Fayetteville, North Carolina, USA*
Latitude: 35.0417°, Longitude: -78.8192°
Elevation: 90.19 ft**
* source: ESRI Maps
** source: USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland
PF_tabular | PF_graphical | Maps_&_aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1
Duration Average recurrence interval (years)
1 2 5 10 25 50 100 200 500 1000
5-min 0.432
(0.392‑0.479)
0.510
(0.462‑0.565)
0.596
(0.540‑0.661)
0.662
(0.598‑0.732)
0.743
(0.668‑0.820)
0.803
(0.720‑0.883)
0.862
(0.768‑0.946)
0.918
(0.815‑1.01)
0.991
(0.872‑1.09)
1.05
(0.916‑1.15)
10-min 0.690
(0.626‑0.765)
0.815
(0.739‑0.903)
0.955
(0.865‑1.06)
1.06
(0.956‑1.17)
1.18
(1.06‑1.31)
1.28
(1.15‑1.41)
1.37
(1.22‑1.50)
1.46
(1.29‑1.60)
1.57
(1.38‑1.72)
1.65
(1.44‑1.81)
15-min 0.862
(0.782‑0.956)
1.02
(0.929‑1.14)
1.21
(1.09‑1.34)
1.34
(1.21‑1.48)
1.50
(1.35‑1.66)
1.62
(1.45‑1.78)
1.73
(1.54‑1.90)
1.84
(1.63‑2.01)
1.97
(1.74‑2.16)
2.07
(1.81‑2.27)
30-min 1.18
(1.07‑1.31)
1.42
(1.28‑1.57)
1.72
(1.55‑1.90)
1.94
(1.75‑2.15)
2.22
(2.00‑2.45)
2.44
(2.19‑2.68)
2.65
(2.36‑2.91)
2.86
(2.54‑3.14)
3.14
(2.76‑3.44)
3.35
(2.93‑3.68)
60-min 1.47
(1.34‑1.63)
1.78
(1.61‑1.97)
2.20
(1.99‑2.44)
2.53
(2.28‑2.80)
2.96
(2.66‑3.27)
3.30
(2.96‑3.63)
3.65
(3.26‑4.01)
4.01
(3.56‑4.40)
4.50
(3.96‑4.93)
4.89
(4.28‑5.37)
2-hr 1.72
(1.52‑1.99)
2.09
(1.85‑2.41)
2.64
(2.34‑3.04)
3.07
(2.71‑3.54)
3.66
(3.21‑4.21)
4.13
(3.61‑4.75)
4.62
(4.01‑5.31)
5.11
(4.42‑5.87)
5.80
(4.96‑6.65)
6.34
(5.39‑7.29)
3-hr 1.82
(1.62‑2.12)
2.21
(1.96‑2.56)
2.81
(2.49‑3.25)
3.29
(2.91‑3.81)
3.97
(3.49‑4.58)
4.53
(3.95‑5.23)
5.12
(4.43‑5.90)
5.74
(4.94‑6.61)
6.62
(5.63‑7.62)
7.34
(6.17‑8.43)
6-hr 2.17
(1.94‑2.48)
2.64
(2.36‑3.00)
3.36
(2.99‑3.81)
3.95
(3.50‑4.48)
4.77
(4.21‑5.40)
5.46
(4.78‑6.16)
6.18
(5.37‑6.98)
6.96
(5.99‑7.84)
8.07
(6.86‑9.07)
8.97
(7.55‑10.1)
12-hr 2.56
(2.29‑2.91)
3.11
(2.77‑3.52)
3.98
(3.54‑4.50)
4.69
(4.16‑5.30)
5.72
(5.02‑6.43)
6.58
(5.74‑7.38)
7.50
(6.48‑8.39)
8.50
(7.27‑9.49)
9.94
(8.39‑11.1)
11.1
(9.28‑12.4)
24-hr 3.03
(2.81‑3.28)
3.67
(3.41‑3.98)
4.71
(4.37‑5.10)
5.55
(5.13‑6.01)
6.74
(6.20‑7.29)
7.72
(7.06‑8.35)
8.75
(7.97‑9.48)
9.86
(8.93‑10.7)
11.4
(10.3‑12.4)
12.7
(11.3‑13.8)
2-day 3.50
(3.27‑3.78)
4.24
(3.95‑4.57)
5.38
(5.00‑5.80)
6.31
(5.85‑6.80)
7.63
(7.03‑8.21)
8.70
(7.98‑9.36)
9.84
(8.97‑10.6)
11.0
(10.0‑11.9)
12.7
(11.5‑13.8)
14.1
(12.6‑15.3)
3-day 3.72
(3.47‑4.00)
4.49
(4.19‑4.83)
5.67
(5.28‑6.09)
6.62
(6.15‑7.11)
7.96
(7.35‑8.54)
9.05
(8.32‑9.71)
10.2
(9.32‑11.0)
11.4
(10.4‑12.3)
13.1
(11.8‑14.2)
14.5
(13.0‑15.7)
4-day 3.93
(3.68‑4.22)
4.74
(4.44‑5.09)
5.95
(5.55‑6.38)
6.93
(6.45‑7.42)
8.29
(7.68‑8.88)
9.39
(8.66‑10.1)
10.6
(9.68‑11.3)
11.8
(10.7‑12.7)
13.5
(12.2‑14.5)
14.8
(13.3‑16.1)
7-day 4.57
(4.26‑4.90)
5.48
(5.11‑5.88)
6.81
(6.34‑7.31)
7.86
(7.31‑8.43)
9.32
(8.63‑10.00)
10.5
(9.68‑11.3)
11.7
(10.8‑12.6)
13.0
(11.9‑14.0)
14.7
(13.4‑15.9)
16.2
(14.6‑17.5)
10-day 5.22
(4.91‑5.58)
6.25
(5.86‑6.67)
7.63
(7.14‑8.14)
8.72
(8.15‑9.29)
10.2
(9.49‑10.9)
11.4
(10.5‑12.1)
12.6
(11.6‑13.4)
13.8
(12.7‑14.8)
15.5
(14.2‑16.6)
16.8
(15.3‑18.1)
20-day 7.02
(6.62‑7.48)
8.35
(7.86‑8.90)
10.0
(9.43‑10.7)
11.4
(10.7‑12.1)
13.2
(12.3‑14.0)
14.6
(13.6‑15.5)
16.0
(14.9‑17.1)
17.5
(16.2‑18.7)
19.5
(17.9‑20.9)
21.1
(19.3‑22.6)
30-day 8.76
(8.27‑9.30)
10.4
(9.79‑11.0)
12.2
(11.5‑13.0)
13.7
(12.9‑14.5)
15.6
(14.6‑16.6)
17.1
(16.0‑18.2)
18.6
(17.3‑19.8)
20.1
(18.7‑21.4)
22.0
(20.4‑23.6)
23.6
(21.7‑25.3)
45-day 11.1
(10.5‑11.7)
13.1
(12.4‑13.8)
15.2
(14.4‑16.1)
16.8
(15.9‑17.8)
19.0
(17.9‑20.1)
20.6
(19.4‑21.8)
22.2
(20.8‑23.5)
23.8
(22.2‑25.3)
25.9
(24.1‑27.6)
27.5
(25.5‑29.3)
60-day 13.3
(12.7‑14.0)
15.6
(14.8‑16.5)
18.0
(17.1‑19.0)
19.8
(18.8‑20.9)
22.1
(20.9‑23.3)
23.9
(22.6‑25.2)
25.6
(24.1‑27.0)
27.3
(25.6‑28.8)
29.5
(27.6‑31.2)
31.1
(29.0‑33.1)
1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency
estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at
upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
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REFERENCE 2

Erosion and Sediment Control Planning and Design Manual,
Chapter 8.03, NCDEQ, Revised May, 2013.

Appendices
8.03 EStImat ING RUNOff
Rev. 6/06 8.03.1
Estimating peak rate of runoff, volume of runoff, and soil loss are basic to the
design of erosion and sedimentation control facilities.
There are a number of acceptable methods of determining runoff. Two
acceptable methods, the rational method and the Natural Resources
Conservation Service (NRCS), formally the SCS, peak discharge method, are
described in this section.
The rational method is very simple in concept but relies on considerable
judgement and experience to evaluate all factors properly. It is used primarily
for small drainage areas (less than 50 acres). The NRCS method is more
sophisticated hydrologically and offers a more accurate approximation of
runoff, particularly for areas larger than 20 acres. Choice of method for small
areas depends primarily on the experience of the designer.
Rational Method
The rational formula is:
Q = CIA
where:
Q = peak rate of runoff in cubic feet per second (cfs)
C = runoff coefficient, an empirical coefficient representing the
relationship between rainfall rate and runoff rate
I = average intensity of rainfall in inches/hour, for a storm duration equal
to the time of concentration, TCA = drainage area in acres
The general procedure for determining peak discharge using the rational
formula is presented below and illustrated in Sample Problem 8.03a.
Step 1. Determine the drainage area in acres.
Step 2. Determine the runoff coefficient, C, for the type of soil/cover in the
drainage area (Table 8.03b).
If the land use and soil cover is homogenous over the drainage area, a C
value can be determined directly from Table 8.03b. If there are multiple soil
cover conditions, a weighted average must be calculated, or the area may be
subdivided.
8
Step 3. Determine the time of concentration, TC, for the drainage area.
Shortcut to Time of Concentration, TC, calculation:
As long as a watershed’s area is less than 4.6S, A(acres) < 4.6 S %, where S
is the slope in percent, the total time of concentration can be taken to be 5
minutes for bare soil. This is helpful to know because it will save the time of
calculating time of concentration by other methods, including the Kinematic
Wave Theory (below) which requires an iterative solution.
The Kinematic Wave Theory defines time of concentration as the “travel time
of a wave to move from the hydraulically most distant point in the catchment
to the outlet (Bedient and Huber, 1992)”. The formula for the time of
concentration for overland flow is:
where:
L = length of overland flow plane (feet)
S = slope (ft/ft)
n = Manning’s roughness
Ii = rainfall intensity
C = rational runoff coefficient
Because both time of concentration and rainfall intensity are unknown
variables in one equation, the solution must be found through iterations. The
use of a spreadsheet is recommended. An example is shown in Table 8.03a.
8.03.2 Rev. 6/07
Appendices
Surface Manning’s “n”
Smooth Surface:
Bare Earth:
Fallow:
Cultivated, < 20% residue:
Cultivated, > 20% residue:
Grass, short:
Grass, dense:
Grass, Bermuda:
Woods, light:
Woods, dense:
0.011
0.020
0.050
0.060
0.170
0.150
0.240
0.410
0.400
0.800
Solving for Time of Concentration (overland flow)
Kinematic Wave Theory
trial time of Duration
Tr (minutes)
Rainfall
Intensity
i (inches/hour)
Calculated time
of Concentration
TC (minutes)
5 7.08 2.90
10 5.66 3.17
15 4.78 3.39
30 3.46 3.86
60 (1 hour)2.25 4.58
Enter the Rainfall Intensity Values for the Corresponding Times of Duration from the Table
8.03c, Intensity Duration Frequency, or the NOAA Precipitation Frequency Data Server,
http://hdsc.nws.noaa.gov/hdsc/pfds/orb/nc_pfds.html. Select the Trial Time of Duration
that is equal to or less than the calculated time of Concentration, or the Calculated time
of Concentration if less than 5 minutes. This is the overland flow component of the Time
of Concentration.
In this example, there is no Trial Time of Duration that is less than corresponding Calculated Time of
Concentration. In this case, select a Rainfall Intensity of 7.08 inches/hour and a Time of Concentration for
Overland Flow of 2.90 minutes.
Length of overland flow:100 feet
Manning’s “n” surface:0.020
Average watershed slope: 0.030 foot per foot
Rational Coefficient:0.33
Rev. 5/08 8.03.3
table 8.03a time of Concentration
8
The above method estimates the time of concentration for overland flow.
After short distances of 400 feet at most, sheet flow tends to concentrate in
rills and then gullies of increasing proportions. Such flow is usually referred
to as shallow concentrated flow (HEC-22, Urban Drainage Manual, FWHA).
The NRCS TR-55 Manual (1986) assumed a maximum sheet flow of 300 feet,
and the more recent WinTR-55 User Manual (2003) allowed no more than 100
feet of overland flow. Shallow concentrated flow is an important component
in determining Time of Concentration.
Both the FWHA and NRCS procedures use similar formulas for the velocity
of shallow concentrated flow, where...
V = 16.1345 * S1/2 (Unpaved)
V = 20.3282 * S1/2 (Paved)
where:
V = average velocity (ft/s), and
S = slope (ft/ft)
Flow in gullies empty into open channels or pipes. Cross-section geometry
and roughness should be obtained for all channel reaches in the watershed.
Manning’s equation can be used to estimate average flow velocities in pipes
and open channels as follows:
V =1.49
n (R)2/3 (S1/2)
where:
n = roughness coefficient
V = velocity (ft/s)
R = hydraulic radius (ft)
S = slope (ft)
For a circular pipe flowing full, the hydraulic radius is one-fourth of the
diameter. For a wide rectangular channel (width > 10 * depth), the hydraulic
radius is approximately equal to the depth.
The travel time for shallow concentrated flow and open channels and pipes
is then calculated from the velocities of those travel segments by the following
equation:
Ti = L
(60 * V)
where:
Ti = travel time for segment i, minutes
L = flow length for segment i, (ft)
8.03.4 Rev. 5/08
Appendices
For short flow lengths, the time of travel in open channels or pipes may not
significantly add to the time of concentration. For longer flow lengths, it may
be more accurate to calculate the kinematic wave speed in the open channel or
pipe rather than the velocity.
The wave travel time in an open channel can be estimated by calculating the
kinematic wave speed in feet per second, converting to feet per minute, and
dividing the length (ft) by the average velocity. The kinematic wave speed, C,
in an open channel is determined by the following equation:
C = V + 32.2 (A) 1/2
WT
where:
C = wave speed (ft/s)
V = velocity (ft/s)
A = the cross-sectional area of flow (ft2)
WT = the top width of the channel flow (ft)
TC = L
60 (C)
where:
TC= Time of Concentration for open channel (minutes)
L = length of channel segment (ft)
C = wave speed (ft/s)
The total time of concentration is the sum of the overland, shallow
concentrated and channel flow times.
Step 4. Determine the rainfall intensity, duration and frequency. The tables
provided were excerpted from the “Precipitation-Frequency Atlas of the United
Sates” NOAA Atlas 14, Volume 2, Version 2, G.M. Bonnin, D. Todd, B. Lin, T.
Parzybok, M. Yekta, and D. Riley, NOAA, National Weather Service, Silver
Spring, Maryland, 2004. An interactive web-site that includes many more
observation records across North Carolina may be used to obtain data for a
more specific locale at http://hdsc.nws.noaa.gov/hdsc/pfds/orb/nc_pfds.html .
Step 5. Determine peak discharge, Q (cubic feet per second), by multiplying
the previously determined factors using the rational formula (Sample Problem
8.03a);
Q =CIA
Rev. 6/06 8.03.5
8
table 8.03b
Value of Runoff Coefficient
(C) for Rational formula
Land Use C Land Use C
Business:
Downtown areas
Neighborhood areas
Residential:
Single-family areas
Multi units, detached
Multi units, Attached
Suburban
Industrial:
Light areas
Heavy areas
Parks, cemeteries
Playgrounds
Railroad yard areas
Unimproved areas
Streets:
Asphalt
Concrete
Brick
Drives and walks
Roofs

0.70-0.95
0.50-0.70

0.30-0.50
0.40-0.60
0.60-0.75
0.25-0.40

0.50-0.80
0.60-0.90
0.10-0.25
0.20-0.35
0.20-0.40
0.10-0.30

0.70-0.95
0.80-0.95
0.70-0.85
0.75-0.85
0.75-0.85
Lawns:
Sandy soil, flat, 2%
Sandy soil, ave.,
2-7%
Sandy soil, steep,
7%
Heavy soil, flat, 2%
Heavy soil, ave.,
2-7%
Heavy soil, steep,
7%
Agricultural land:
Bare packed soil
Smooth
Rough
Cultivated rows
Heavy soil no crop
Heavy soil with
crop
Sandy soil no crop
Sandy soil with
crop
Pasture
Heavy soil
Sandy soil
Woodlands

0.05-0.10
0.10-0.15

0.15-0.20

0.13-0.17
0.18-0.22

0.25-0.35

0.30-0.60
0.20-0.50

0.30-0.60

0.20-0.50
0.20-0.40

0.10-0.25

0.15-0.45
0.05-0.25
0.05-0.25
NOTE: The designer must use judgement to select the appropriate C
value within the range for the appropriate land use. Generally, larger
areas with permeable soils, flat slopes, and dense vegetation should
have lowest C values. Smaller areas with slowly permeable soils, steep
slopes, and sparse vegetation should be assigned highest C values.
Source: American Society of Civil Engineers
8.03.6 Rev. 6/06
Appendices
Solution:
(1) Drainage area: 20 acres (given)
(2) Determine runoff coefficient, C.
Calculate Weighted Average
area C from table 8.03b
Graded1 12 x 0.45 = 5.4
Woodland 8 x 0.15 = 1.2
20 6.6
C = 6.6/20 = 0.33
(3) Find the overland time of concentration using iterations of the
kinematic wave equation (Table 8.03a) using a slope length of
100 ft for overland flow and 300 feet for shallow concentrated
flow (unpaved). The average watershed slope is 3%. Assume
overland flow on bare earth. Work an example with the
spreadsheet (pasted in below)
NOTE: Any time of flow in shallow concentrated flow or channel flow
should be added to the overland flow to determine TC.
To find the time of flow in shallow concentrated flow, use
the procedures from FWHA and NRCS described on page
8.03.4.
First, calculate the velocity of the shallow concentrated flow:
The travel time for shallow concentrated flow may then be
calculated for the segment by:
Rev. 6/06 8.03.7
Sample Problem 8.03a
Determination of Peak
Runoff Rate Using the
Rational method
Q = CIA
Given:
Drainage area: 20 acres
Graded areas: 12 acres
Woodland: 8 acres
Maximum slope length: 100 ft overland flow, 300 ft shallow
concentrated flow
Average slope: 3%, area bare
Location: Raleigh, NC
find:
Peak runoff rate from 10-year frequency storm
8.03.8 Rev. 5/08
8
The total time of concentration, TC, may be found by summing the TC for
overland flow and the travel time in shallow concentrated flow:
TC = TC (overland) + TC (shallow concentrated) + TC (channel)
TC = 2.90 minutes + 1.79 minutes
TC = 4.7 minutes, Use 5 minutes as the minimum TC
I = 7.08 inches/hour (from Table 8.03C) using a 10-year
storm, 5 minute duration.
(4) Q = CIA
Q = 0.33*7.08*20 = 46.7cfs, Use 47 cfs.
8.03.9
Murphy, North Carolina 35.0961N, 84.0239W
aRI*
(years)
5 min. 10 min. 15 min. 30 min. 60 min. 120 min. 3 hr. 6 hr. 12 hr. 24 hr.
2 4.93 3.94 3.30 2.28 1.43 0.89 0.62 0.38 0.24 0.15
10 6.78 5.42 4.57 3.31 2.16 1.29 0.92 0.55 0.34 0.21
25 7.90 6.29 5.31 3.94 2.62 1.57 1.13 0.68 0.41 0.25
100 9.62 7.64 6.44 4.93 3.40 2.06 1.50 0.90 0.53 0.33
asheville, North Carolina 35.4358N, 82.5392W
aRI*
(years)
5 min. 10 min. 15 min. 30 min. 60 min. 120 min. 3 hr. 6 hr. 12 hr. 24 hr.
2 5.21 4.16 3.46 2.41 1.51 0.89 0.63 0.38 0.24 0.14
10 7.06 5.65 4.76 3.45 2.25 1.30 0.91 0.55 0.34 0.20
25 8.09 6.44 5.45 4.03 2.69 1.56 1.10 0.66 0.40 0.24
100 9.68 7.69 6.48 4.96 3.42 2.00 1.43 0.86 0.50 0.30
Boone, North Carolina 36.2167N, 81.6667W
aRI*
(years)
5 min. 10 min. 15 min. 30 min. 60 min. 120 min. 3 hr. 6 hr. 12 hr. 24 hr.
2 5.71 4.57 3.83 2.64 1.66 1.00 0.72 0.48 0.31 0.18
10 7.50 6.00 5.06 3.67 2.39 1.46 1.06 0.69 0.44 0.28
25 8.59 6.85 5.78 4.28 2.85 1.77 1.29 0.83 0.52 0.34
100 10.38 8.25 6.95 5.32 3.67 2.35 1.72 1.08 0.65 0.44
Charlotte, North Carolina, 35.2333N, 80.85W
aRI*
(years)
5 min. 10 min. 15 min. 30 min. 60 min. 120 min. 3 hr. 6 hr. 12 hr. 24 hr.
2 5.68 4.54 3.80 2.63 1.65 0.96 0.68 0.41 0.24 0.14
10 7.26 5.80 4.89 3.55 2.31 1.36 0.98 0.59 0.35 0.20
25 8.02 6.38 5.40 4.00 2.66 1.59 1.15 0.70 0.42 0.24
100 9.00 7.15 6.03 4.62 3.18 1.93 1.43 0.87 0.53 0.30
Greensboro, North Carolina 36.975N, 79.9436W
aRI*
(years)
5 min. 10 min. 15 min. 30 min. 60 min. 120 min. 3 hr. 6 hr. 12 hr. 24 hr.
2 5.46 4.36 3.66 2.52 1.58 0.93 0.66 0.40 0.23 0.14
10 6.85 5.48 4.62 3.35 2.18 1.30 0.92 0.56 0.33 0.20
25 7.39 5.89 4.98 3.69 2.46 1.49 1.06 0.65 0.39 0.23
100 7.93 6.30 5.31 4.07 2.80 1.75 1.24 0.78 0.48 0.29
* ARI is the Average Return Interval.
** Intensity Duration Frequency table is measured in inches per hour.
table 8.03c Intensity Duration Frequency
For use with Rational Method**
8
8.03.10 Rev. 6/06
Raleigh, North Carolina 35.8706N, 78.7864W
aRI*
(years)
5 min. 10 min. 15 min. 30 min. 60 min. 120 min. 3 hr. 6 hr. 12 hr. 24 hr.
2 5.58 4.46 3.74 2.58 1.62 0.94 0.66 0.40 0.24 0.14
10 7.08 5.66 4.78 3.46 2.25 1.33 0.95 0.58 0.34 0.021
25 7.78 6.19 5.24 3.88 2.58 1.54 1.11 0.68 0.41 0.24
100 8.64 6.86 5.78 4.43 3.05 1.85 1.36 0.84 0.51 0.30
Fayetteville, North Carolina 35.0583N, 78.8583W
aRI*
(years)
5 min. 10 min. 15 min. 30 min. 60 min. 120 min. 3 hr. 6 hr. 12 hr. 24 hr.
2 6.11 4.88 4.09 2.83 1.77 1.04 0.74 0.44 0.26 0.15
10 7.96 6.36 5.36 3.88 2.53 1.54 1.10 0.66 0.39 0.23
25 8.94 7.13 6.02 4.46 2.97 1.83 1.32 0.80 0.47 0.28
100 10.44 8.29 6.99 5.35 3.69 2.29 1.69 1.03 0.62 0.36
Wilmington, North Carolina 34.2683N, 77.9061W
aRI*
(years)
5 min. 10 min. 15 min. 30 min. 60 min. 120 min. 3 hr. 6 hr. 12 hr. 24 hr.
2 7.39 5.92 4.96 3.42 2.15 1.28 0.91 0.56 0.33 0.19
10 9.70 7.75 6.54 4.74 3.08 1.94 1.39 0.87 0.51 0.30
25 10.98 8.75 7.40 5.48 3.65 2.38 1.73 1.08 0.64 0.38
100 12.92 10.27 8.65 6.63 4.56 3.18 2.37 1.49 0.89 0.53
Washington, North Carolina 35.5333N, 77.0167W
aRI*
(years)
5 min. 10 min. 15 min. 30 min. 60 min. 120 min. 3 hr. 6 hr. 12 hr. 24 hr.
2 6.41 5.12 4.29 2.96 1.86 1.10 0.78 0.47 0.27 0.16
10 8.38 6.70 5.65 4.09 2.66 1.64 1.19 0.72 0.42 0.25
25 9.48 7.55 6.38 4.73 3.15 1.99 1.46 0.88 0.52 0.31
100 11.16 8.87 7.47 5.72 3.94 2.58 1.93 1.18 0.70 0.42
manteo airport, North Carolina 35.9167N, 75.7000W
aRI*
(years)
5 min. 10 min. 15 min. 30 min. 60 min. 120 min. 3 hr. 6 hr. 12 hr. 24 hr.
2 6.46 5.16 4.32 2.99 1.87 1.08 0.79 0.48 0.29 0.17
10 8.47 6.77 5.71 4.14 2.69 1.62 1.20 0.74 0.44 0.27
25 9.56 7.62 6.44 4.77 3.17 1.96 1.47 0.91 0.54 0.33
100 11.26 8.95 7.54 5.77 3.98 2.54 1.95 1.21 0.73 0.44
Cape Hatteras, North Carolina, 35.2322N, 75.6225W
aRI*
(years)
5 min. 10 min. 15 min. 30 min. 60 min. 120 min. 3 hr. 6 hr. 12 hr. 24 hr.
2 7.20 5.75 4.82 3.33 2.09 1.29 0.94 0.58 0.34 0.20
10 9.41 7.52 6.35 4.60 2.99 1.93 1.43 0.89 0.53 0.31
25 10.66 8.49 7.18 5.31 3.54 2.33 1.75 1.09 0.65 0.38
100 12.53 9.95 8.39 6.42 4.42 3.03 2.32 1.45 0.88 0.51
Appendices
Rev. 6/06 8.03.11
8
8.03.12 Rev. 6/06
SCS (NRCS) Peak Discharge Method
Equation 8.03a
Equation 8.03b
Equation 8.03c
Equation 8.03d
Technical Release 55 (TR-55) presents simplified procedures for estimating
runoff and peak discharges in small watersheds. In selecting the appropriate
procedure, consider the scope and complexity of the problem, the available
data, and the acceptable level of error. While this TR gives special emphasis to
urban and urbanizing watersheds, the procedures apply to any small watershed
in which certain limitations are met. The following excerpt presents the portion
of TR-55 for determining peak discharge. New rainfall data from NOAA is
presented in tabular form.
SCS runoff curve number method
The SCS Runoff Curve Number (CN) method is described in detail in NEH-4
(SCS 1985). The SCS runoff equation is:
Q = (P – Ia)2
(P – Ia) + S
where:
Q = runoff (in)
P = rainfall (in)
S = potential maximum retention after runoff begins (in) and
Ia = initial abstraction (in)
Initial abstraction (Ia) is all losses before runoff begins. It includes water
retained in surface depressions, water intercepted by vegetation, evaporation,
and infiltration. Ia is highly variable but generally is correlated with soil and
cover parameters. Through studies of many small agricultural watersheds, Ia
was found to be approximated by the following empirical equation:
Ia = 0.2S
By removing Ia as an independent parameter, this approximation allows use
of a combination of S and P to produce a unique runoff amount. Substituting
equation 8.03b into equation 8.03a gives:
Q =(P – 0.2S)2
(P + 0.8S)
S is related to the soil and cover conditions of the watershed through the CN.
CN has a range of 0 to 100, and S is related to CN by:
S =1000 – 10 CN
Figure 8.03a and Table 8.03d solve equations 8.03c and 8.03d for a range of
CN’s and rainfall.
Appendices
Rev. 6/06 8.03.13
Factors considered in determining runoff curve numbers
The major factors that determine CN are the hydrologic soil group (HSG),
cover type, treatment, hydrologic condition, and antecedent runoff condition
(ARC). Another factor considered is whether impervious areas outlet directly
to the drainage system (connected) or whether the flow spreads over pervious
areas before entering the drainage system (unconnected). Figure 8.03b is
provided to aid in selecting the appropriate figure or table for determining
curve numbers.
CN’s in Tables 8.03e-8.03g represent average antecedent runoff condition
for urban, cultivated agricultural, other agricultural, and arid and semiarid
rangeland uses. Table 8.03c assumes impervious areas are directly connected.
The following sections explain how to determine CN’s and how to modify
them for urban conditions.
Hydrologic soil groups
Infiltration rates of soils vary widely and are affected by subsurface permeability
as well as surface intake rates. Soils are classified into four HSG’s (A, B, C,
and D) according to their minimum infiltration rate, which is obtained for bare
soil after prolonged wetting. The soils in the area of interest may be identified
from a soil survey report, which can be obtained from local SCS offices or soil
and water conservation district offices.
Most urban areas are only partially covered by impervious surfaces: the soil
remains an important factor in runoff estimates. Urbanization has a greater
effect on runoff in watersheds with soils having high infiltration rates (sands
and gravels) than in watersheds predominantly of silts and clays, which
generally have low infiltration rates.
Any disturbance of a soil profile can significantly change its infiltration
characteristics. With urbanization, native soil profiles may be mixed or
removed or fill material from other areas may be introduced.
8
8.03.14 Rev. 6/06
Cover type
Table 8.03e addresses most cover types, such as vegetation, bare soil, and
impervious surfaces. There are a number of methods for determining cover
type. The most common are field reconnaissance, aerial photographs, and land
use maps.
Treatment
Treatment is a cover type modifier (used only in Table 8.03f) to describe the
management of cultivated agricultural lands. It includes mechanical practices,
such as contouring and terracing, and management practices, such as crop
rotations and reduced or no tillage.
Hydrologic condition
Hydrologic condition indicates the effects of cover type and treatment on
infiltration and runoff and is generally estimated from density of plant and
residue cover on sample areas. Good hydrologic condition indicates that the
soil usually has a low runoff potential for that specific hydrologic soil group,
cover type, and treatment. Some factors to consider in estimating the effect of
cover on infiltration and runoff are (a) canopy or density of lawns, crops, or
other vegetative areas; (b) amount of year-round cover; (c) amount of grass or
close-seeded legumes in rotations; (d) percent of residue cover; and (e) degree
of surface roughness.
figure 8.03a Solution of runoff equation
Appendices
Rev. 6/06 8.03.15
table 8.03d Runoff depth for selected CN’s and rainfall amounts 1
Runoff depth for curve number of—
Rainfall 40 45 50 55 60 65 70 75 80 85 90 95 98
------------------------------------------------------------inches-----------------------------------------------------------
1.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.03 0.08 0.17 0.32 0.56 0.79
1.2 0.00 0.00 0.00 0.00 0.00 0.00 .03 .07 .15 .27 .46 .74 .99
1.4 0.00 0.00 0.00 0.00 0.00 .02 .06 .13 .24 .39 .61 .92 1.18
1.6 0.00 0.00 0.00 0.00 .01 .05 .11 .20 .34 .52 .76 1.11 1.38
1.8 0.00 0.00 0.00 0.00 .03 .09 .17 .29 .44 .65 .93 1.29 1.58
2.0 0.00 0.00 0.00 .02 .06 .14 .24 .38 .56 .80 1.09 1.48 1.77
2.5 0.00 0.00 .02 .08 .17 .30 .46 .65 .89 1.18 1.53 1.96 2.27
3.0 0.00 .02 .09 .19 .33 .51 .71 .96 1.25 1.59 1.98 2.45 2.77
3.5 .02 .08 .20 .35 .53 .75 1.01 1.30 1.64 2.02 2.45 2.94 3.27
4.0 .06 .18 .33 .53 .76 1.03 1.33 1.67 2.04 2.46 2.92 3.43 3.77
4.5 .14 .30 .50 .74 1.02 1.33 1.67 2.05 2.46 2.91 3.40 3.92 4.26
5.0 .24 .44 .69 .98 1.30 1.65 2.04 2.45 2.89 3.37 3.88 4.42 4.76
6.0 .50 .80 1.14 1.52 1.92 2.35 2.81 3.28 3.78 4.30 4.85 5.41 5.76
7.0 .84 1.24 1.68 2.12 2.60 3.10 3.62 4.15 4.69 5.25 5.82 6.41 6.76
8.0 1.25 1.74 2.25 2.78 3.33 3.89 4.46 5.04 5.63 6.21 6.81 7.40 7.76
9.0 1.71 2.29 2.88 3.49 4.10 4.72 5.33 5.95 6.57 7.18 7.79 8.40 8.76
10.0 2.23 2.89 3.56 4.23 4.90 5.56 6.22 6.88 7.52 8.16 8.78 9.40 9.76
11.0 2.78 3.52 4.26 5.00 5.72 6.43 7.13 7.81 8.48 9.13 9.77 10.39 10.76
12.0 3.38 4.19 5.00 5.79 6.56 7.32 8.05 8.76 9.45 10.11 10.76 11.39 11.76
13.0 4.00 4.89 5.76 6.61 7.42 8.21 8.98 9.71 10.42 11.10 11.76 12.39 12.76
14.0 4.65 5.62 6.55 7.44 8.30 9.12 9.91 10.67 11.39 12.08 12.75 13.39 13.76
15.0 5.33 6.36 7.35 8.29 9.19 10.04 10.85 11.63 12.37 13.07 13.74 14.39 14.76
1 / Interpolate the values shown to obtain runoff depths for CN’s or rainfall amounts not shown.
8
8.03.16 Rev. 6/06
figure 8.03b Flow chart for selecting the appropriate figure or table for determining runoff curve numbers
Unconnected
impervious
area?
Yes
Impervious
area
< 30%
Impervious
area
< 30%
Determine
pervious
CN
(table 8.03e)
START
Determine
pervious
CN
(table 8.03e)
Determine
pervious
CN
(figure 8.03b)
Determine
composite
CN
(figure 8.03c)
Determine
composite
CN
(figure 8.03d)
END
No
No Yes
No
Yes
Appendices
Rev. 6/06 8.03.17
table 8.03e Runoff curve numbers of urban areas1
---------------------------------------Cover Description-------------------------
Curve number for
---------hydrologic soil group--------
Cover type and hydrologic condition Average percent
impervious area2 ABCD
Fully developed urban areas (vegetation established)
Open space (lawns, parks, golf courses, cemeteries, etc.) 3:
Poor condition (grass cover < 50%) .............................68 79 86 89
Fair condition (grass cover 50% to 75%) .....................49 69 79 84
Good condition (grass cover > 75%) ............................39 61 74 80
Impervious areas:
Paved parking lots, roofs, driveways, etc.
(excluding right-of-way) ...............................................98 98 98 98
Streets and roads:
Paved; curbs and storm sewers (excluding
right-of-way) ..................................................................98 98 98 98
Paved; open ditches (including right-of-way) ................83 89 92 93
Gravel (including right-of-way) ......................................76 85 89 91
Dirt (including right-of-way) ...........................................72 82 87 89
Urban districts:
Commercial and business ................................................. 85 89 92 94 95
Industrial ...........................................................................72 81 88 91 93
Residential districts by average lot size:
1/8 acre or less (town houses) ......................................... 65 77 85 90 92
1/4 acre ............................................................................ 38 61 75 83 87
1/3 acre .............................................................................30 57 72 81 86
1/2 acre .............................................................................25 54 70 80 85
1 acre ...............................................................................20 51 68 79 84
2 acres ..............................................................................12 46 65 77 82
Developing urban areas
Newly graded areas
(pervious areas only, no vegetation) 4 ..............................77 86 91 94
Idle lands (CN’s are determined using cover types
similar to those in table 2-2c).
1. Average runoff condition, and Ia = 0.2S.
2. The average percent impervious area shown was used to develop the composite CN’s. Other assumptions are as follows: impervious
areas are directly connected to the drainage system, impervious areas have a CN of 98, and pervious areas are considered equivalent
to open space in good hydrologic condition. CN’s for other combinations of conditions may be computed using Figure 8.03c or 8.03d.
3. CN’s shown are equivalent to those of pasture. Composite CN’s may be computed for other combinations of open space cover type.
4. Composite CN’s to use for the design of temporary measures during grading and construction should be computed using Figure 8.03c
or 8.03d based on the degree of development (impervious area percentage) and the CN’s for the newly graded pervious areas.
8
8.03.18 Rev. 6/06
table 8.03f Runoff curve numbers for cultivated agriculture lands1
---------------------------Cover description-------------------------------
Curve numbers for
--------------hydrologic soil groups-----------
Cover type Treatments
2
Hydrologic
conditions3 ABCD
Fallow Bare soil ————— 77 86 91 94
Row crops Straight row Good 67 78 85 89
Contoured &
terraced
Good 62 71 78 81
1 Average runoff condition, and Ia=0.2S
2 Crop residue cover applies only if residue is on at least 5% of the surface throughout the year.
3 Hydraulic condition is based on combination factors that affect infiltration and runoff, including (a) density
and canopy of vegetative areas, (b) amount of year-round cover, (c) amount of grass or close-seeded
legumes, (d) percent of residue cover on the land surface (good ≥ 20%), and (e) degree of surface
roughness.
Poor: Factors impair infiltration and tend to increase runoff.
Good: Factors encourage average and better than average infiltration and tend to decrease runoff.
Appendices
Rev. 6/06 8.03.19
table 8.03g Runoff curve numbers for other agriculture lands1
---------------------------Cover description-------------------------------
Curve numbers for
--------------hydrologic soil groups-----------
Cover type
Hydrologic
conditions3 ABCD
Pasture, grassland, or range—
continuous forage for grazing. 2
Poor 68 79 86 89
Fair 49 69 79 84
Good 39 61 74 80
Meadow—continuous grass, protected
from grazing and generally mowed for
hay.
— 30 58 71 78
Brush—brush-weed-grass mixture with
brush the major element. 3
Poor 48 67 77 83
Fair 35 56 70 77
Good 30 4 48 65 73
Woods—grass combination (orchard or
tree farm). 5
Poor 57 73 82 86
Fair 43 65 76 82
Good 32 58 72 79
Woods. 6 Poor 45 66 77 83
Fair 36 60 73 79
Good 30 4 55 70 77
Farmsteads—buildings, lanes,
driveways, and surrounding lots.
— 59 74 82 86
1 Average runoff condition, and Ia = 0.2S.
2 Poor: <50% ground cover or heavily grazed with no mulch.
Fair: 50 to 75% ground cover and not heavily grazed.
Good: > 75% ground cover and lightly or only occasionally grazed.
3 Poor: <50% ground cover.
Fair: 50 to 75% ground cover.
Good: >75% ground cover.
4 Actual curve number is less than 30; use CN = 30 for runoff computations.
5 CN’s shown were computed for areas with 50% woods and 50% grass (pasture) cover. Other combinations of
conditions may be computed from the CN’s for woods and pasture.
6 Poor: Forest litter, small trees, and brush are destroyed by heavy grazing or regular burning.
Fair: Woods are grazed but not burned, and some forest litter covers the soil.
Good: Woods are protected from grazing, and litter and brush adequately cover the soil.
8
8.03.20 Rev. 6/06
Urban impervious area modifications
Several factors, such as the percentage of impervious area and the means of
conveying runoff from impervious areas to the drainage system, should be
considered in computing CN for urban areas (Rawls et al., 1981). For example,
do the impervious areas connect directly to the drainage system, or do they
outlet onto lawns or other pervious areas where infiltration can occur?
Connected impervious areas — An impervious area is considered connected
if runoff from it flows directly into the drainage system. It is also considered
connected if runoff from it occurs as concentrated shallow flow that runs over
a pervious area and then into the drainage system.
Urban CN’s (Table 8.03e) were developed for typical land use relationships
based on specific assumed percentages of impervious area. These CN vales
were developed on the assumptions that (a) pervious urban areas are equivalent
to pasture in good hydrologic condition and (b) impervious areas have a
CN of 98 and are directly connected to the drainage system. Some assumed
percentages of impervious area are shown in Table 8.03e.
If all of the impervious area is directly connected to the drainage system, but
the impervious area percentages or the pervious land use assumptions in Table
8.03e are not applicable, use Figure 8.03c to compute a composite CN. For
example, Table 8.03e gives a CN of 70 for a 1/2-acre lot in HSG B, with
assumed impervious area of 25 percent. However, if the lot has 20 percent
impervious area and a pervious area CN of 61, the composite CN obtained
from Figure 8.03c is 68. The CN difference between 70 and 68 reflects the
difference in percent impervious area.
Unconnected impervious areas — Runoff from these areas is spread over a
pervious area as sheet flow. To determine CN when all or part of the impervious
area is not directly connected to the drainage system, (1) use Figure 8.03d if
total impervious area is less than 30 percent or (2) use Figure 8.03c if the total
impervious area is equal to or greater than 30 percent, because the absorptive
capacity of the remaining pervious areas will not significantly affect runoff.
When impervious area is less than 30 percent, obtain the composite CN by
entering the right half of Figure 8.03d with the percentage of total impervious
area and the ratio of total unconnected impervious area to total impervious
area. Then move left to the appropriate pervious CN and read down to find
the composite CN. For example, for a 1/2-acre lot with 20 percent total
impervious area (75 percent of which is unconnected) and pervious CN of
61, the composite CN from Figure 8.03d is 66. If all of the impervious area is
connected, the resulting CN (from Figure 8.03c) would be 68.
Appendices
Rev. 6/06 8.03.21
figure 8.03c Composite CN with connected impervious area
figure 8.03d Composite CN with unconnected impervious areas and total impervious are
less than 30%
Previous CN = 90
80
70
60
50
400 10 20 30 40 50 60 70 80 90 100
100
90
80
70
60
50
40Composite CNConnected impervious area (percent)Prev
ious
CN
=
40
5060708090
90 80 70 60 50 40 0 10 20 30
1.0
0.5
0.0
Composite CN Total impervious
area (percent)(Unconnected impervious)(Total impervious)
8
8.03.22 Rev. 6/06
Runoff
When CN and the amount of rainfall have been determined for the watershed,
determine runoff depth by using Figure 8.03a, Table 8.03d, or equations 8.03c
and 8.03d. The runoff is usually rounded to the nearest hundredth of an inch.
Limitations
• Curve numbers describe average conditions that are useful for design
purposes. If the rainfall event used is a historical storm, the modeling
accuracy decreases.
• Use the runoff curve number equation with caution when re-creating
specific features of an actual storm. The equation does not contain an
expression for time and, therefore, does not account for rainfall duration
or intensity.
• The user should understand the assumption reflected in the initial
abstraction term (Ia) and should ascertain that the assumption applies to
the situation. Ia, which consists of interception, initial infiltration, surface
depression storage, evapotranspiration, and other factors, was generalized
as 0.2S based on data from agricultural watersheds (S is the potential
maximum retention after runoff begins). This approximation can be
especially important in an urban application because the combination of
impervious areas with pervious areas can imply a significant initial loss
that may not take place. The opposite effect, a greater initial loss, can
occur if the impervious areas have surface depressions that store some
runoff. To use a relationship other than Ia = 0.2S, one must redevelop
equation 8.03c, Figure 8.03a, Table 8.03d, and Table 8.03e by using the
original rainfall-runoff data to establish new S or CN relationships for
each cover and hydrologic soil group.
• Runoff from snowmelt or rain on frozen ground cannot be estimated using
these procedures.
• The CN procedure is less accurate when runoff is less than 0.5 inch. As a
check, use another procedure to determine runoff.
• The SCS runoff procedures apply only to direct surface runoff: do not
overlook large sources of subsurface flow or high ground water levels that
contribute to runoff. These conditions are often related to HSG A soils and
forest areas that have been assigned relatively low CN’s in Table 8.03e.
Good judgment and experience based on stream gage records are needed
to adjust CN’s as conditions warrant.
• When the weighted CN is less than 40, use another procedure to determine
runoff.
Appendices
Rev. 6/06 8.03.23
Example 8.03a
The example below illustrates the procedure for computing runoff curve
number (CN) and runoff (Q) in inches. Worksheet 2 is provided to assist TR-
55 users.
The watershed covers 250 acres in Dyer County, northwestern Tennessee.
Seventy percent (175 acres) is a Loring soil, which is in hydrologic soil group
C. Thirty percent (75 acres) is a Memphis soil, which is in group B. The event
is a 25-year frequency, 24-hour storm with total rainfall of 6 inches.
Seventy percent (175 acres) of the watershed, consisting of all the Memphis
soil and 100 acres of the Loring soil, is 1/2-acre residential lots with lawns in
good hydrologic condition. The rest of the watershed is scattered open space
in good hydrologic condition. (See Figure 8.03e).
8
8.03.24 Rev. 6/06
Worksheet 1: Runoff curve number and runoff
Project Heavenly Acres By WJR Date 10/1/2006
Location Dare County, North Carolina Checked NM Date 10/3/2006
Check one: Present Developed 175 Acres residential
1. Runoff curve number
Soil name
and
hydrologic
group
Cover description
(cover type, treatment, and hydrologic
condition; percent impervious;
unconnected/connected impervious area
ratio)
CN 1 Area
acres
mi2
%
Product
of
CN x area
Table 8.03eFigure 8.03cFigure 8.03dMemphis, B 25% impervious
1/2 acre lots, good condition
70 75 5250
Loring, C 25% impervious
1/2 acre lots, good condition
80 100 8000
Loring, C Open space, good condition 74 75 5550
1: Use only one CN source per line totals 25 18,800
CN (weighted) =total product =18,800 =75.2 Use CN 75
total area 2500
2. Runoff
Storm #1 Storm #2 Storm #3
Frequency ...................... yr 25
Rainfall, P (24-hr) ........... in 6.0
Runoff, Q ........................ in 3.28
(Use P and CN with table 8.03d,
figure 8.03a, or equations 8.03c
and 8.03d)
X
X
figure 8.03e Worksheet 1 for example 8.03a
Appendices
Rev. 6/06 8.03.25
Worksheet 1: Runoff curve number and runoff
Project By Date
Location Checked Date
Check one: Present Developed
1. Runoff curve number
Soil name
and
hydrologic
group
Cover description
(cover type, treatment, and hydrologic condition;
percent impervious; unconnected/connected
impervious area ratio)
CN 1 Area
acres
mi2
%
Product
of
CN x area
Table 8.03eFigure 8.03cFigure 8.03d1: Use only one CN source per line totals 
CN (weighted) =total product ==Use CN 
total area
2. Runoff
Storm #1 Storm #2 Storm #3
Frequency ...................... yr
Rainfall, P (24-hr) ........... in
Runoff, Q ........................ in
(Use P and CN with table 8.03d, figure
8.03a, or equations 8.03c and 8.03d)
8
8.03.26 Rev. 6/06
Time of Concentration and Travel Time
Travel time ( Tt ) is the time it takes water to travel from one location to
another in a watershed. Tt is a component of time of concentration ( Tc ),
which is the time for runoff to travel from the hydraulically most distant point
of the watershed to a point of interest within the watershed. Tc is computed
by summing all the travel times for consecutive components of the drainage
conveyance system.
Tc influences the shape and peak of the runoff hydrograph. Urbanization
usually decreases Tc, thereby increasing the peak discharge. But Tc can be
increased as a result of (a) ponding behind small or inadequate drainage
systems, including storm drain inlets and road culverts, or (b) reduction of
land slope through grading.
Factors affecting time of concentration and travel time
Surface roughness
One of the most significant effects of urban development on flow velocity is
less retardance to flow. That is, undeveloped areas with very slow and shallow
overland flow through vegetation become modified by urban development: the
flow is then delivered to streets, gutters, and storm sewers that transport runoff
downstream more rapidly. Travel time through the watershed is generally
decreased.
Channel shape and flow patterns
In small non-urban watersheds, much of the travel time results from overland
flow in upstream areas. Typically, urbanization reduces overland flow lengths
by conveying storm runoff into a channel as soon as possible. Since channel
designs have efficient hydraulic characteristics, runoff flow velocity increases
and travel time decreases.
Slope
Slopes may be increased or decreased by urbanization, depending on the extent
of site grading or the extent to which storm sewers and street ditches are used
in the design of the water management system. Slope will tend to increase
when channels are straightened and decrease when overland flow is directed
through storm sewers, street gutters, and diversions.
Computation of travel time and time of concentration
Water moves through a watershed as sheet flow, shallow concentrated flow,
open channel flow, or some combination of these. The type that occurs is a
function of the conveyance system and is best determined by field inspection.
Appendices
Rev. 6/06 8.03.27
Travel time ( Tt ) is the ratio of flow length to flow velocity:
Equation 8.03e
Tt =L
3600V
where:
Tt = Travel time (hr)
L = flow length (ft)
V = average velocity (ft/s)
3600 = conversion factor from seconds to hours
Equation 8.03f
Time of concentration (Tc) is the sum of Tt values for the various consecutive
flow segments:
Tc = Tt1 + Tt2 + ... Ttm
where:
Tc = time of concentration (hr)
m = number of flow segments
Sheet flow
Sheet flow is flow over plane surfaces. It usually occurs in the headwater
of streams. With sheet flow, the friction value (Manning’s n) is an effective
roughness coefficient that includes the effect of raindrop impact; drag over the
plane surface; obstacles such as litter, crop ridges, and rocks; and erosion and
transportation of sediment. These n values are for very shallow flow depths of
about 0.1 foot or so. Table 8.03h gives Manning’s n values for sheet flow for
various surface conditions.
8
figure 8.03f Average velocities for estimating travel time for shallow concentrated flow
8.03.28 Rev. 6/06
.50
.20
.10
.08
.04
.02
.01
.005
1 2 4 6 10 20
Average velocity (ft/sec)Watercourse slope (ft/ft)UnpavedPaved
Appendices
table 8.03h Roughness
coefficients (Manning’s n)
for sheet flow
Surface description n1
Smooth surface (concrete, asphalt, gravel, or bare
soil) 0.011
Fallow (no residue) ................................................
........0.05
Cultivated soils:
Residue cover ≤ 20% ..........................................
Residue cover > 20% ...........................................

0.06
0.17
Grass:
Short grass prairies .............................................
Dense grasses2 ....................................................
Bermudagrass ......................................................

0.15
0.24
0.41
Range (nutral) .........................................................0.13
Woods: 3
Light underbrush .................................................
Dense underbrush ...............................................

0.40
0.80
1 The n values are a composite of information compiled by Engman (1986).
2 Includes species such as weeping lovegrass, bluegrass, buffalo grass, blue grama
grass, and native grass mixtures.
3 When selecting n , consider cover to a height of about 0.1 ft. This is the only part of
the plant cover that will obstruct sheet flow.
For sheet flow of less than 300 feet, use Manning’s kinematic solution
(Overtop and Meadows 1976) to compute Tt:
Equation 8.03g Tt =0.007(nL)0.8
(P2)0.5s0.4
where:
Tt = Travel time (hr)
n = Manning’s roughness coefficient (Table 8.03h)
L = flow length (ft)
P2 = 2-year, 24-hour rainfall (in)
s = slope of hydraulic grade line (land slope, ft/ft)
This simplified form of the Manning’s kinematic solution is based on the
following: (1) shallow steady uniform flow, (2) constant intensity of rainfall
excess (that part of a rain available for runoff), (3) rainfall duration of 24
hours, and (4) minor effect of infiltration on travel time.
Rev. 6/06 8.03.29
8
Shallow concentrated flow
After a maximum of 300 feet, sheet flow usually becomes shallow concentrated
flow. The average velocity for this flow can be determined from Figure 8.03f, in
which average velocity is a function of watercourse slope and type of channel.
Tillage can affect the direction of shallow concentrated flow. Flow may not
always be directly down the watershed slope if tillage runs across the slope.
After determining average velocity in Figure 8.03f, use equation 8.03e to
estimate travel time for the shallow concentrated flow segment.
Open channels
Open channels are assumed to begin where surveyed cross section information
has been obtained, where channels are visible on aerial photographs, or where
blue lines (indicating streams) appear on United States Geological Survey
(USGS) quadrangle sheets. Manning’s equation or water surface profile
information can be used to estimate average flow velocity. Average flow
velocity is usually determined for bankfull elevation.
Manning’s equation is:
Equation 8.03h V =1.49r⅔s½
n
where:
V = average velocity (ft/s)
r = hydralic radius (ft) and is equal to a/pw
a = cross sectional flow area (ft2)
pw = wetted perimeter (ft)
s = slope of hydraulic grade line (land slope, ft/ft)
n = Manning’s roughness coefficient for open channel flow
Manning’s n values for open channel flow can be obtained from standard
textbooks such as Chow (1959) or Linsley et al. (1982). After average velocity
is computed using equation 8.03h, Tt for the channel segment can be estimated
using equation 8.03e.
Reservoirs or lakes
Sometimes it is necessary to estimate the velocity of flow through a reservoir
or lake at the outlet of a watershed. This travel time is normally very small and
can be assumed as zero.
Limitations
• Manning’s kinematic solution should not be used for sheet flow longer
than 300 feet. Equation 8.03g was developed for use with the four standard
rainfall intensity-duration relationships.
• In watersheds with storm sewers, carefully identify the appropriate
hydraulic flow path to estimate Tc. Storm sewers generally handle only a
small portion of a large event. The rest of the peak flow travels by streets,
lawns, and so on, to the outlet. Consult a standard hydraulics textbook
to determine average velocity in pipes for either pressure or nonpressure
flow.
8.03.30 Rev. 6/06
Appendices
• The minimum Tc used in TR-55 is 0.1 hour.
• A culvert or bridge can act as a reservoir outlet if there is significant
storage behind it. The procedures in TR-55 can be used to determine the
peak flow upstream of the culvert. Detailed storage routing procedures
should be used to determine the outflow through the culvert.
Example 8.03b
The sketch below shows a watershed in Dyer County, northwestern Tennessee.
The problem is to compute Tc at the outlet of the watershed (point D). The 2-
year 24-hour rainfall depth is 3.6 inches. All three types of flow occur from the
hydraulically most distant point (A) to the point of interest (D). To compute
Tc, first determine Tt for each segment from the following information:
Segment AB: Sheet flow; dense grass; slope (s) = 0.01 ft/ft; and length (L) =
100 ft. Segment BC: Shallow concentrated flow; unpaved; s = 0.01 ft/ft; and L
= 1,400 ft. Segment CD: Channel flow; Manning’s n = .05; flow area (a) = 27
ft2; wetted perimeter (pw) = 28.2 ft; s = 0.005 ft/ft; and L = 7,300 ft.
See Figure 8.03h for the computations made on worksheet 2.
Figure 8.03g
Rev. 6/06 8.03.31
100 ft
B
7,300 ft1,400 ft
DCA
Not to scale
8
Worksheet 2: Time of Concentration (Tc) or travel time (tt)
Project Heavenly Acres By DW Date 10/6/2006
Location Dare County, North Carolina Checked NM Date 10/8/2006
Check one: Present Developed
Check one: Tc Tt through subarea
Note: Space for as many as two segments per flow can be used for each worksheet.
Include a map, schematic, or description of flow segments.
Sheet flow (Applicable to Tc only)
Segment ID: AB
1. Surface description (table 8.03h) ..........................Dense Grass
2. Manning’s roughness coefficient, n (table 8.03h)...0.24
3. Flow length, L (total L + 300ft) ..........................ft 100
4. Two-year 24-hour rainfall, P2 ...........................in 3.6
5. Land slope, s .................................................ft/ft 0.01
6. Tt =0.007 (nL)0.8
Compute Tt ..............hr 0.30 +=0.30 P20.5s0.4
Shallow concentrated flow
Segment ID:BC
7. Surface description (paved or unpaved).............Unpaved
8. Flow length, L ...................................................ft 1400
9. Watercourse slope, s ....................................ft/ft 0.01
10. Average velocity, V (figure 3-1) ...................ft/s 1.6
11. Tt =L Compute Tt ..............hr 0.24 +=0.243600 V
Channel flow
Segment ID: CD
12. Cross sectional flow area, a ..........................ft2 27
13. Wetted perimeter, Pw ......................................ft 28.2
14. Hydraulic radius, r =a Compute r .........ft 0.957Pw
15. Channel slope, s .........................................ft/ft 0.005
16. Manning’s roughness coeficient, n ...................0.05
17. V =1.49r⅔s½
Compute V .............ft/s 2.05n
18. Flow length, L .................................................ft 7300
19. Tt =L Compute Tt ..............hr 0.99 +=0.993600V
20. Watershed or subarea or (add in step 6,11, and 19) ..............................................................Hr 1.53
X
X
figure 8.03h Worksheet 2 for example 8.03b
8.03.32 Rev. 6/06
Worksheet 2: Time of Concentration (Tc) or travel time (tt)
Project By Date
Location Checked Date
Check one: Present Developed
Check one: Tc Tt through subarea
Note: Space for as many as two segments per flow can be used for each worksheet.
Include a map, schematic, or description of flow segments.
Sheet flow (Applicable to Tc only)
Segment ID:
1. Surface description (table 8.03h)........................
2. Manning’s roughness coefficient, n (table 8.03h)
3. Flow length, L (total L + 300ft) ..........................ft
4. Two-year 24-hour rainfall, P2 ...........................in
5. Land slope, s .................................................ft/ft
6. Tt =0.007 (nL)0.8
Compute Tt ..............hr += P20.5s0.4
Shallow concentrated flow
Segment ID:
7. Surface description (paved or unpaved).............
8. Flow length, L ...................................................ft
9. Watercourse slope, s ....................................ft/ft
10. Average velocity, V (figure 3-1) ...................ft/s
11. Tt =L Compute Tt ..............hr +=3600 V
Channel flow
Segment ID:
12. Cross sectional flow area, a ..........................ft2
13. Wetted perimeter, Pw ......................................ft
14. Hydraulic radius, r =a Compute r .........ftPw
15. Channel slope, s .........................................ft/ft
16. Manning’s roughness coeficient, n ...................
17. V =1.49r⅔s½
Compute V .............ft/sn
18. Flow length, L .................................................ft
19. Tt =L Compute Tt ..............hr +=3600V
20. Watershed or subarea or (add in step 6,11, and 19) ................................................................Hr
Rev. 6/06 8.03.33

REFERENCE 3

NRCS Web Soil Survey, Cumberland County, Accessed August 21,
2018.

Soil Map—Cumberland County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/21/2018
Page 1 of 338798003879900388000038801003880200388030038804003879800387990038800003880100388020038803003880400698200698300698400698500698600698700698800698900699000699100
698200 698300 698400 698500 698600 698700 698800 698900 699000 699100
35° 2' 49'' N 78° 49' 40'' W35° 2' 49'' N78° 49' 1'' W35° 2' 28'' N
78° 49' 40'' W35° 2' 28'' N
78° 49' 1'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 17N WGS84
0 200 400 800 1200
Feet
0 50 100 200 300
Meters
Map Scale: 1:4,520 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Cumberland County, North Carolina
Survey Area Data: Version 18, Sep 26, 2017
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Aug 13, 2014—Feb
4, 2017
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Soil Map—Cumberland County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/21/2018
Page 2 of 3
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
AaA Altavista fine sandy loam, 0 to
3 percent slopes, rarely
flooded, Southern Coastal
Plain
18.0 24.0%
Cf Cape Fear loam 1.3 1.8%
Ro Roanoke and Warne soils, 0 to
2 percent slopes,
occasionally flooded
15.5 20.6%
TaB Tarboro loamy sand, 0 to 6
percent slopes
9.6 12.7%
WmB Wickham fine sandy loam, 1 to
6 percent slopes, rarely
flooded
30.8 41.0%
Totals for Area of Interest 75.2 100.0%
Soil Map—Cumberland County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/21/2018
Page 3 of 3

REFERENCE 4

HydroCAD Reports, S&ME Inc., August 2018.

1S
Ex 122S
2S
Ex 123S
3S
Ex 121S
4S
Ex 124S
Routing Diagram for Cumberland Existing Watersheds
Prepared by S&ME, Inc., Printed 8/29/2018
HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Subcat Reach Pond Link
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Existing Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 2HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method
Runoff Area=196,500 sf 0.00% Impervious Runoff Depth>0.16"Subcatchment 1S: Ex 122S
Flow Length=387' Tc=15.2 min CN=55 Runoff=0.36 cfs 0.061 af
Runoff Area=3.720 ac 0.00% Impervious Runoff Depth>0.77"Subcatchment 2S: Ex 123S
Flow Length=957' Tc=56.8 min CN=73 Runoff=1.61 cfs 0.237 af
Runoff Area=1,071,488 sf 0.00% Impervious Runoff Depth>0.41"Subcatchment 3S: Ex 121S
Flow Length=940' Tc=43.6 min CN=64 Runoff=5.46 cfs 0.836 af
Runoff Area=135,955 sf 0.00% Impervious Runoff Depth>0.41"Subcatchment 4S: Ex 124S
Flow Length=670' Tc=32.4 min CN=64 Runoff=0.86 cfs 0.107 af
Total Runoff Area = 35.950 ac Runoff Volume = 1.241 af Average Runoff Depth = 0.41"
100.00% Pervious = 35.950 ac 0.00% Impervious = 0.000 ac
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Existing Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 3HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment 1S: Ex 122S
Runoff =0.36 cfs @ 12.17 hrs, Volume=0.061 af, Depth> 0.16"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-yr Rainfall=3.03"
Area (sf) CN Description
112,211 39 >75% Grass cover, Good, HSG A
20,212 74 >75% Grass cover, Good, HSG C
4,748 30 Woods, Good, HSG A
59,329 80 >75% Grass cover, Good, HSG D
196,500 55 Weighted Average
196,500 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet)(ft/ft) (ft/sec)(cfs)
9.4 100 0.0190 0.18 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.66"
5.8 287 0.0140 0.83 Shallow Concentrated Flow, Shallow Concentrated Flow
Short Grass Pasture Kv= 7.0 fps
15.2 387 Total
Subcatchment 1S: Ex 122S
Runoff
Hydrograph
Time (hours)
201918171615141312111098765Flow (cfs)0.4
0.38
0.36
0.34
0.32
0.3
0.28
0.26
0.24
0.22
0.2
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
Type II 24-hr
1-yr Rainfall=3.03"
Runoff Area=196,500 sf
Runoff Volume=0.061 af
Runoff Depth>0.16"
Flow Length=387'
Tc=15.2 min
CN=55
0.36 cfs
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Existing Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 4HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment 2S: Ex 123S
Runoff =1.61 cfs @ 12.64 hrs, Volume=0.237 af, Depth> 0.77"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-yr Rainfall=3.03"
Area (ac) CN Description
0.640 61 >75% Grass cover, Good, HSG B
2.600 74 >75% Grass cover, Good, HSG C
0.480 80 >75% Grass cover, Good, HSG D
3.720 73 Weighted Average
3.720 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet)(ft/ft) (ft/sec)(cfs)
16.0 100 0.0050 0.10 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.66"
40.8 857 0.0025 0.35 Shallow Concentrated Flow, Shallow Concentrated Flow
Short Grass Pasture Kv= 7.0 fps
56.8 957 Total
Subcatchment 2S: Ex 123S
Runoff
Hydrograph
Time (hours)
201918171615141312111098765Flow (cfs)1
0
Type II 24-hr
1-yr Rainfall=3.03"
Runoff Area=3.720 ac
Runoff Volume=0.237 af
Runoff Depth>0.77"
Flow Length=957'
Tc=56.8 min
CN=73
1.61 cfs
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Existing Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 5HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment 3S: Ex 121S
Runoff =5.46 cfs @ 12.52 hrs, Volume=0.836 af, Depth> 0.41"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-yr Rainfall=3.03"
Area (sf) CN Description
74,923 55 Woods, Good, HSG B
95,832 39 >75% Grass cover, Good, HSG A
459,122 61 >75% Grass cover, Good, HSG B
426,278 74 >75% Grass cover, Good, HSG C
15,333 80 >75% Grass cover, Good, HSG D
1,071,488 64 Weighted Average
1,071,488 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet)(ft/ft) (ft/sec)(cfs)
10.3 100 0.0150 0.16 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.66"
33.3 840 0.0036 0.42 Shallow Concentrated Flow, Shallow Concentrated Flow
Short Grass Pasture Kv= 7.0 fps
43.6 940 Total
Subcatchment 3S: Ex 121S
Runoff
Hydrograph
Time (hours)
201918171615141312111098765Flow (cfs)6
5
4
3
2
1
0
Type II 24-hr
1-yr Rainfall=3.03"
Runoff Area=1,071,488 sf
Runoff Volume=0.836 af
Runoff Depth>0.41"
Flow Length=940'
Tc=43.6 min
CN=64
5.46 cfs
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Existing Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 6HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment 4S: Ex 124S
Runoff =0.86 cfs @ 12.35 hrs, Volume=0.107 af, Depth> 0.41"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-yr Rainfall=3.03"
Area (sf) CN Description
114,178 61 >75% Grass cover, Good, HSG B
21,777 80 >75% Grass cover, Good, HSG D
135,955 64 Weighted Average
135,955 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet)(ft/ft) (ft/sec)(cfs)
13.2 100 0.0080 0.13 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.66"
19.2 570 0.0050 0.49 Shallow Concentrated Flow, Shallow Concentrated Flow
Short Grass Pasture Kv= 7.0 fps
32.4 670 Total
Subcatchment 4S: Ex 124S
Runoff
Hydrograph
Time (hours)
201918171615141312111098765Flow (cfs)0.95
0.9
0.85
0.8
0.75
0.7
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
Type II 24-hr
1-yr Rainfall=3.03"
Runoff Area=135,955 sf
Runoff Volume=0.107 af
Runoff Depth>0.41"
Flow Length=670'
Tc=32.4 min
CN=64
0.86 cfs
2S
Post 222S
3S
Post 221S
4P
North Pond 222S
10P
South Pond 221S
Routing Diagram for Cumberland Proposed Watersheds
Prepared by S&ME, Inc., Printed 8/29/2018
HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Subcat Reach Pond Link
Type II 24-hr 1" Rainfall=1.00"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 2HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Time span=0.00-120.00 hrs, dt=0.05 hrs, 2401 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method
Runoff Area=313,435 sf 81.72% Impervious Runoff Depth=0.50"Subcatchment 2S: Post 222S
Flow Length=1,187' Slope=0.0030 '/' Tc=38.1 min CN=94 Runoff=2.65 cfs 0.302 af
Runoff Area=1,193,196 sf 45.77% Impervious Runoff Depth=0.17"Subcatchment 3S: Post 221S
Flow Length=979' Tc=33.1 min CN=85 Runoff=2.80 cfs 0.396 af
Peak Elev=92.35' Storage=8,197 cf Inflow=2.65 cfs 0.302 afPond 4P: North Pond 222S
Primary=0.16 cfs 0.300 af Secondary=0.00 cfs 0.000 af Outflow=0.16 cfs 0.300 af
Peak Elev=92.16' Storage=12,312 cf Inflow=2.80 cfs 0.396 afPond 10P: South Pond 221S
Primary=0.13 cfs 0.369 af Secondary=0.00 cfs 0.000 af Outflow=0.13 cfs 0.369 af
Total Runoff Area = 34.587 ac Runoff Volume = 0.698 af Average Runoff Depth = 0.24"
46.76% Pervious = 16.171 ac 53.24% Impervious = 18.416 ac
Type II 24-hr 1" Rainfall=1.00"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 3HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment 2S: Post 222S
Runoff =2.65 cfs @ 12.35 hrs, Volume=0.302 af, Depth= 0.50"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 1" Rainfall=1.00"
Area (sf) CN Description
*256,133 98 Impervious/Gravel
13,841 94 Fallow, bare soil, HSG D
8,700 77 Fallow, bare soil, HSG A
8,364 61 >75% Grass cover, Good, HSG B
26,397 74 >75% Grass cover, Good, HSG C
313,435 94 Weighted Average
57,302 18.28% Pervious Area
256,133 81.72% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet)(ft/ft) (ft/sec)(cfs)
19.6 100 0.0030 0.09 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.66"
9.2 212 0.0030 0.38 Shallow Concentrated Flow, Shallow Concentrated Flow
Short Grass Pasture Kv= 7.0 fps
9.3 875 0.0030 1.58 31.51 Channel Flow, Channel Flow
Area= 20.0 sf Perim= 21.0' r= 0.95' n= 0.050
38.1 1,187 Total
Subcatchment 2S: Post 222S
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)2
1
0
Type II 24-hr
1" Rainfall=1.00"
Runoff Area=313,435 sf
Runoff Volume=0.302 af
Runoff Depth=0.50"
Flow Length=1,187'
Slope=0.0030 '/'
Tc=38.1 min
CN=94
2.65 cfs
Type II 24-hr 1" Rainfall=1.00"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 4HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment 3S: Post 221S
Runoff =2.80 cfs @ 12.35 hrs, Volume=0.396 af, Depth= 0.17"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 1" Rainfall=1.00"
Area (sf) CN Description
*546,068 98 Impervious/Gravel
68,651 55 Woods, Good, HSG B
153,070 61 >75% Grass cover, Good, HSG B
192,012 74 >75% Grass cover, Good, HSG C
5,053 80 >75% Grass cover, Good, HSG D
11,674 39 >75% Grass cover, Good, HSG A
108,334 91 Fallow, bare soil, HSG C
108,334 86 Fallow, bare soil, HSG B
1,193,196 85 Weighted Average
647,128 54.23% Pervious Area
546,068 45.77% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet)(ft/ft) (ft/sec)(cfs)
1.1 100 0.0212 1.51 Sheet Flow, Sheet Flow
Smooth surfaces n= 0.011 P2= 3.66"
2.9 171 0.0038 0.99 Shallow Concentrated Flow, Shallow Concentrated Flow
Unpaved Kv= 16.1 fps
0.4 150 0.0220 5.84 70.07 Channel Flow, Channel Flow
Area= 12.0 sf Perim= 11.0' r= 1.09' n= 0.040
0.1 24 0.0083 2.82 4.98 Pipe Channel, CMP_Round 18"
18.0" Round Area= 1.8 sf Perim= 4.7' r= 0.38'
n= 0.025 Corrugated metal
22.9 384 0.0016 0.28 Shallow Concentrated Flow, Shallow Concentrated Flow #2
Short Grass Pasture Kv= 7.0 fps
0.2 32 0.0063 2.45 4.34 Pipe Channel, CMP_Round 18"
18.0" Round Area= 1.8 sf Perim= 4.7' r= 0.38'
n= 0.025 Corrugated metal
5.5 118 0.0026 0.36 Shallow Concentrated Flow, Shallow Concentrated Flow #3
Short Grass Pasture Kv= 7.0 fps
33.1 979 Total
Type II 24-hr 1" Rainfall=1.00"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 5HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Subcatchment 3S: Post 221S
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)3
2
1
0
Type II 24-hr
1" Rainfall=1.00"
Runoff Area=1,193,196 sf
Runoff Volume=0.396 af
Runoff Depth=0.17"
Flow Length=979'
Tc=33.1 min
CN=85
2.80 cfs
Type II 24-hr 1" Rainfall=1.00"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 6HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Summary for Pond 4P: North Pond 222S
Inflow Area =7.195 ac, 81.72% Impervious, Inflow Depth = 0.50" for 1" event
Inflow =2.65 cfs @ 12.35 hrs, Volume=0.302 af
Outflow =0.16 cfs @ 15.80 hrs, Volume=0.300 af, Atten= 94%, Lag= 206.9 min
Primary =0.16 cfs @ 15.80 hrs, Volume=0.300 af
Secondary =0.00 cfs @ 0.00 hrs, Volume=0.000 af
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 92.35' @ 15.80 hrs Surf.Area= 20,433 sf Storage= 8,197 cf
Plug-Flow detention time= 735.0 min calculated for 0.300 af (99% of inflow)
Center-of-Mass det. time= 733.4 min ( 1,592.8 - 859.4 )
Volume Invert Avail.Storage Storage Description
#1 91.75'292,552 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet)(sq-ft)(cubic-feet)(cubic-feet)
91.75 9,466 0 0
92.00 11,699 2,646 2,646
93.00 36,975 24,337 26,983
94.00 110,221 73,598 100,581
95.10 238,818 191,971 292,552
Device Routing Invert Outlet Devices
#1 Secondary 94.00'50.0' long x 5.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00
2.50 3.00 3.50 4.00 4.50 5.00 5.50
Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65
2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88
#2 Device 3 91.75'3.0" Round Culvert L= 2.0' RCP, sq.cut end projecting, Ke= 0.500
Inlet / Outlet Invert= 91.20' / 91.75' S= -0.2750 '/' Cc= 0.900
n= 0.010 PVC, smooth interior, Flow Area= 0.05 sf
#3 Primary 91.50'6.0" Round Culvert
L= 35.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 91.50' / 91.50' S= 0.0000 '/' Cc= 0.900
n= 0.010 PVC, smooth interior, Flow Area= 0.20 sf
#4 Device 3 94.50'24.0" x 36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=0.16 cfs @ 15.80 hrs HW=92.35' (Free Discharge)
3=Culvert (Passes 0.16 cfs of 0.52 cfs potential flow)
2=Culvert (Inlet Controls 0.16 cfs @ 3.30 fps)
4=Orifice/Grate ( Controls 0.00 cfs)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=91.75' (Free Discharge)
1=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
Type II 24-hr 1" Rainfall=1.00"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 7HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Pond 4P: North Pond 222S
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)2
1
0
Inflow Area=7.195 ac
Peak Elev=92.35'
Storage=8,197 cf
2.65 cfs
0.16 cfs
0.16 cfs
0.00 cfs
Type II 24-hr 1" Rainfall=1.00"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 8HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Summary for Pond 10P: South Pond 221S
Inflow Area =27.392 ac, 45.77% Impervious, Inflow Depth = 0.17" for 1" event
Inflow =2.80 cfs @ 12.35 hrs, Volume=0.396 af
Outflow =0.13 cfs @ 24.25 hrs, Volume=0.369 af, Atten= 95%, Lag= 714.2 min
Primary =0.13 cfs @ 24.25 hrs, Volume=0.369 af
Secondary =0.00 cfs @ 0.00 hrs, Volume=0.000 af
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 92.16' @ 24.25 hrs Surf.Area= 32,689 sf Storage= 12,312 cf
Plug-Flow detention time= 1,377.1 min calculated for 0.369 af (93% of inflow)
Center-of-Mass det. time= 1,342.0 min ( 2,265.2 - 923.2 )
Volume Invert Avail.Storage Storage Description
#1 91.75'209,231 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet)(sq-ft)(cubic-feet)(cubic-feet)
91.75 28,892 0 0
92.00 29,510 7,300 7,300
93.00 49,240 39,375 46,675
94.00 275,871 162,556 209,231
Device Routing Invert Outlet Devices
#1 Secondary 93.30'50.0' long x 5.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00
2.50 3.00 3.50 4.00 4.50 5.00 5.50
Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65
2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88
#2 Device 3 91.75'3.0" Round Culvert L= 2.0' RCP, sq.cut end projecting, Ke= 0.500
Inlet / Outlet Invert= 91.20' / 91.75' S= -0.2750 '/' Cc= 0.900
n= 0.010 PVC, smooth interior, Flow Area= 0.05 sf
#3 Primary 91.50'6.0" Round Culvert
L= 30.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 91.50' / 91.50' S= 0.0000 '/' Cc= 0.900
n= 0.012 Steel, smooth, Flow Area= 0.20 sf
#4 Device 3 94.50'24.0" x 36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=0.13 cfs @ 24.25 hrs HW=92.16' (Free Discharge)
3=Culvert (Passes 0.13 cfs of 0.35 cfs potential flow)
2=Culvert (Inlet Controls 0.13 cfs @ 2.58 fps)
4=Orifice/Grate ( Controls 0.00 cfs)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=91.75' (Free Discharge)
1=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
Type II 24-hr 1" Rainfall=1.00"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 9HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Pond 10P: South Pond 221S
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)3
2
1
0
Inflow Area=27.392 ac
Peak Elev=92.16'
Storage=12,312 cf
2.80 cfs
0.13 cfs
0.13 cfs
0.00 cfs
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 10HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Time span=0.00-120.00 hrs, dt=0.05 hrs, 2401 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method
Runoff Area=313,435 sf 81.72% Impervious Runoff Depth=2.38"Subcatchment 2S: Post 222S
Flow Length=1,187' Slope=0.0030 '/' Tc=38.1 min CN=94 Runoff=12.35 cfs 1.427 af
Runoff Area=1,193,196 sf 45.77% Impervious Runoff Depth=1.61"Subcatchment 3S: Post 221S
Flow Length=979' Tc=33.1 min CN=85 Runoff=35.78 cfs 3.683 af
Peak Elev=93.41' Storage=48,314 cf Inflow=12.35 cfs 1.427 afPond 4P: North Pond 222S
Primary=0.29 cfs 1.420 af Secondary=0.00 cfs 0.000 af Outflow=0.29 cfs 1.420 af
Peak Elev=93.43' Storage=88,619 cf Inflow=35.78 cfs 3.683 afPond 10P: South Pond 221S
Primary=0.29 cfs 1.854 af Secondary=5.41 cfs 1.692 af Outflow=5.70 cfs 3.547 af
Total Runoff Area = 34.587 ac Runoff Volume = 5.110 af Average Runoff Depth = 1.77"
46.76% Pervious = 16.171 ac 53.24% Impervious = 18.416 ac
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 11HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment 2S: Post 222S
Runoff =12.35 cfs @ 12.33 hrs, Volume=1.427 af, Depth= 2.38"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-yr Rainfall=3.03"
Area (sf) CN Description
*256,133 98 Impervious/Gravel
13,841 94 Fallow, bare soil, HSG D
8,700 77 Fallow, bare soil, HSG A
8,364 61 >75% Grass cover, Good, HSG B
26,397 74 >75% Grass cover, Good, HSG C
313,435 94 Weighted Average
57,302 18.28% Pervious Area
256,133 81.72% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet)(ft/ft) (ft/sec)(cfs)
19.6 100 0.0030 0.09 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.66"
9.2 212 0.0030 0.38 Shallow Concentrated Flow, Shallow Concentrated Flow
Short Grass Pasture Kv= 7.0 fps
9.3 875 0.0030 1.58 31.51 Channel Flow, Channel Flow
Area= 20.0 sf Perim= 21.0' r= 0.95' n= 0.050
38.1 1,187 Total
Subcatchment 2S: Post 222S
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)13
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
1-yr Rainfall=3.03"
Runoff Area=313,435 sf
Runoff Volume=1.427 af
Runoff Depth=2.38"
Flow Length=1,187'
Slope=0.0030 '/'
Tc=38.1 min
CN=94
12.35 cfs
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 12HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment 3S: Post 221S
Runoff =35.78 cfs @ 12.28 hrs, Volume=3.683 af, Depth= 1.61"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-yr Rainfall=3.03"
Area (sf) CN Description
*546,068 98 Impervious/Gravel
68,651 55 Woods, Good, HSG B
153,070 61 >75% Grass cover, Good, HSG B
192,012 74 >75% Grass cover, Good, HSG C
5,053 80 >75% Grass cover, Good, HSG D
11,674 39 >75% Grass cover, Good, HSG A
108,334 91 Fallow, bare soil, HSG C
108,334 86 Fallow, bare soil, HSG B
1,193,196 85 Weighted Average
647,128 54.23% Pervious Area
546,068 45.77% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet)(ft/ft) (ft/sec)(cfs)
1.1 100 0.0212 1.51 Sheet Flow, Sheet Flow
Smooth surfaces n= 0.011 P2= 3.66"
2.9 171 0.0038 0.99 Shallow Concentrated Flow, Shallow Concentrated Flow
Unpaved Kv= 16.1 fps
0.4 150 0.0220 5.84 70.07 Channel Flow, Channel Flow
Area= 12.0 sf Perim= 11.0' r= 1.09' n= 0.040
0.1 24 0.0083 2.82 4.98 Pipe Channel, CMP_Round 18"
18.0" Round Area= 1.8 sf Perim= 4.7' r= 0.38'
n= 0.025 Corrugated metal
22.9 384 0.0016 0.28 Shallow Concentrated Flow, Shallow Concentrated Flow #2
Short Grass Pasture Kv= 7.0 fps
0.2 32 0.0063 2.45 4.34 Pipe Channel, CMP_Round 18"
18.0" Round Area= 1.8 sf Perim= 4.7' r= 0.38'
n= 0.025 Corrugated metal
5.5 118 0.0026 0.36 Shallow Concentrated Flow, Shallow Concentrated Flow #3
Short Grass Pasture Kv= 7.0 fps
33.1 979 Total
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 13HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Subcatchment 3S: Post 221S
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
1-yr Rainfall=3.03"
Runoff Area=1,193,196 sf
Runoff Volume=3.683 af
Runoff Depth=1.61"
Flow Length=979'
Tc=33.1 min
CN=85
35.78 cfs
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 14HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Summary for Pond 4P: North Pond 222S
Inflow Area =7.195 ac, 81.72% Impervious, Inflow Depth = 2.38" for 1-yr event
Inflow =12.35 cfs @ 12.33 hrs, Volume=1.427 af
Outflow =0.29 cfs @ 20.27 hrs, Volume=1.420 af, Atten= 98%, Lag= 476.5 min
Primary =0.29 cfs @ 20.27 hrs, Volume=1.420 af
Secondary =0.00 cfs @ 0.00 hrs, Volume=0.000 af
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 93.41' @ 20.27 hrs Surf.Area= 67,022 sf Storage= 48,314 cf
Plug-Flow detention time= 1,797.1 min calculated for 1.420 af (100% of inflow)
Center-of-Mass det. time= 1,793.9 min ( 2,609.4 - 815.4 )
Volume Invert Avail.Storage Storage Description
#1 91.75'292,552 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet)(sq-ft)(cubic-feet)(cubic-feet)
91.75 9,466 0 0
92.00 11,699 2,646 2,646
93.00 36,975 24,337 26,983
94.00 110,221 73,598 100,581
95.10 238,818 191,971 292,552
Device Routing Invert Outlet Devices
#1 Secondary 94.00'50.0' long x 5.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00
2.50 3.00 3.50 4.00 4.50 5.00 5.50
Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65
2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88
#2 Device 3 91.75'3.0" Round Culvert L= 2.0' RCP, sq.cut end projecting, Ke= 0.500
Inlet / Outlet Invert= 91.20' / 91.75' S= -0.2750 '/' Cc= 0.900
n= 0.010 PVC, smooth interior, Flow Area= 0.05 sf
#3 Primary 91.50'6.0" Round Culvert
L= 35.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 91.50' / 91.50' S= 0.0000 '/' Cc= 0.900
n= 0.010 PVC, smooth interior, Flow Area= 0.20 sf
#4 Device 3 94.50'24.0" x 36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=0.29 cfs @ 20.27 hrs HW=93.41' (Free Discharge)
3=Culvert (Passes 0.29 cfs of 1.06 cfs potential flow)
2=Culvert (Inlet Controls 0.29 cfs @ 5.97 fps)
4=Orifice/Grate ( Controls 0.00 cfs)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=91.75' (Free Discharge)
1=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 15HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Pond 4P: North Pond 222S
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)13
12
11
10
9
8
7
6
5
4
3
2
1
0
Inflow Area=7.195 ac
Peak Elev=93.41'
Storage=48,314 cf
12.35 cfs
0.29 cfs
0.29 cfs
0.00 cfs
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 16HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Summary for Pond 10P: South Pond 221S
Inflow Area =27.392 ac, 45.77% Impervious, Inflow Depth = 1.61" for 1-yr event
Inflow =35.78 cfs @ 12.28 hrs, Volume=3.683 af
Outflow =5.70 cfs @ 13.24 hrs, Volume=3.547 af, Atten= 84%, Lag= 57.6 min
Primary =0.29 cfs @ 13.24 hrs, Volume=1.854 af
Secondary =5.41 cfs @ 13.24 hrs, Volume=1.692 af
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 93.43' @ 13.24 hrs Surf.Area= 146,411 sf Storage= 88,619 cf
Plug-Flow detention time= 1,391.8 min calculated for 3.545 af (96% of inflow)
Center-of-Mass det. time= 1,372.2 min ( 2,222.8 - 850.5 )
Volume Invert Avail.Storage Storage Description
#1 91.75'209,231 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet)(sq-ft)(cubic-feet)(cubic-feet)
91.75 28,892 0 0
92.00 29,510 7,300 7,300
93.00 49,240 39,375 46,675
94.00 275,871 162,556 209,231
Device Routing Invert Outlet Devices
#1 Secondary 93.30'50.0' long x 5.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00
2.50 3.00 3.50 4.00 4.50 5.00 5.50
Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65
2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88
#2 Device 3 91.75'3.0" Round Culvert L= 2.0' RCP, sq.cut end projecting, Ke= 0.500
Inlet / Outlet Invert= 91.20' / 91.75' S= -0.2750 '/' Cc= 0.900
n= 0.010 PVC, smooth interior, Flow Area= 0.05 sf
#3 Primary 91.50'6.0" Round Culvert
L= 30.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 91.50' / 91.50' S= 0.0000 '/' Cc= 0.900
n= 0.012 Steel, smooth, Flow Area= 0.20 sf
#4 Device 3 94.50'24.0" x 36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=0.29 cfs @ 13.24 hrs HW=93.43' (Free Discharge)
3=Culvert (Passes 0.29 cfs of 1.00 cfs potential flow)
2=Culvert (Inlet Controls 0.29 cfs @ 6.00 fps)
4=Orifice/Grate ( Controls 0.00 cfs)
Secondary OutFlow Max=5.40 cfs @ 13.24 hrs HW=93.43' (Free Discharge)
1=Broad-Crested Rectangular Weir (Weir Controls 5.40 cfs @ 0.84 fps)
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
Page 17HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Pond 10P: South Pond 221S
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Inflow Area=27.392 ac
Peak Elev=93.43'
Storage=88,619 cf
35.78 cfs
5.70 cfs
0.29 cfs
5.41 cfs
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Stage-Area-Storage for Pond 10P: South Pond 221S
Elevation
(feet)
Surface
(sq-ft)
Storage
(cubic-feet)
91.75 28,892 0
91.76 28,917 289
91.77 28,941 578
91.78 28,966 868
91.79 28,991 1,158
91.80 29,016 1,448
91.81 29,040 1,738
91.82 29,065 2,028
91.83 29,090 2,319
91.84 29,114 2,610
91.85 29,139 2,902
91.86 29,164 3,193
91.87 29,189 3,485
91.88 29,213 3,777
91.89 29,238 4,069
91.90 29,263 4,362
91.91 29,288 4,654
91.92 29,312 4,947
91.93 29,337 5,241
91.94 29,362 5,534
91.95 29,386 5,828
91.96 29,411 6,122
91.97 29,436 6,416
91.98 29,461 6,711
91.99 29,485 7,005
92.00 29,510 7,300
92.01 29,707 7,596
92.02 29,905 7,894
92.03 30,102 8,194
92.04 30,299 8,496
92.05 30,496 8,800
92.06 30,694 9,106
92.07 30,891 9,414
92.08 31,088 9,724
92.09 31,286 10,036
92.10 31,483 10,350
92.11 31,680 10,666
92.12 31,878 10,984
92.13 32,075 11,303
92.14 32,272 11,625
92.15 32,470 11,949
92.16 32,667 12,274
92.17 32,864 12,602
92.18 33,061 12,932
92.19 33,259 13,263
92.20 33,456 13,597
92.21 33,653 13,932
92.22 33,851 14,270
92.23 34,048 14,609
92.24 34,245 14,951
92.25 34,443 15,294
92.26 34,640 15,640
Elevation
(feet)
Surface
(sq-ft)
Storage
(cubic-feet)
92.27 34,837 15,987
92.28 35,034 16,336
92.29 35,232 16,688
92.30 35,429 17,041
92.31 35,626 17,396
92.32 35,824 17,754
92.33 36,021 18,113
92.34 36,218 18,474
92.35 36,415 18,837
92.36 36,613 19,202
92.37 36,810 19,569
92.38 37,007 19,939
92.39 37,205 20,310
92.40 37,402 20,683
92.41 37,599 21,058
92.42 37,797 21,435
92.43 37,994 21,814
92.44 38,191 22,195
92.45 38,389 22,577
92.46 38,586 22,962
92.47 38,783 23,349
92.48 38,980 23,738
92.49 39,178 24,129
92.50 39,375 24,522
92.51 39,572 24,916
92.52 39,770 25,313
92.53 39,967 25,712
92.54 40,164 26,112
92.55 40,361 26,515
92.56 40,559 26,920
92.57 40,756 27,326
92.58 40,953 27,735
92.59 41,151 28,145
92.60 41,348 28,558
92.61 41,545 28,972
92.62 41,743 29,389
92.63 41,940 29,807
92.64 42,137 30,227
92.65 42,335 30,650
92.66 42,532 31,074
92.67 42,729 31,500
92.68 42,926 31,929
92.69 43,124 32,359
92.70 43,321 32,791
92.71 43,518 33,225
92.72 43,716 33,661
92.73 43,913 34,100
92.74 44,110 34,540
92.75 44,308 34,982
92.76 44,505 35,426
92.77 44,702 35,872
92.78 44,899 36,320
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Stage-Area-Storage for Pond 10P: South Pond 221S (continued)
Elevation
(feet)
Surface
(sq-ft)
Storage
(cubic-feet)
92.79 45,097 36,770
92.80 45,294 37,222
92.81 45,491 37,676
92.82 45,689 38,132
92.83 45,886 38,590
92.84 46,083 39,049
92.85 46,280 39,511
92.86 46,478 39,975
92.87 46,675 40,441
92.88 46,872 40,909
92.89 47,070 41,378
92.90 47,267 41,850
92.91 47,464 42,324
92.92 47,662 42,799
92.93 47,859 43,277
92.94 48,056 43,756
92.95 48,254 44,238
92.96 48,451 44,721
92.97 48,648 45,207
92.98 48,845 45,694
92.99 49,043 46,184
93.00 49,240 46,675
93.01 51,506 47,179
93.02 53,773 47,705
93.03 56,039 48,254
93.04 58,305 48,826
93.05 60,572 49,421
93.06 62,838 50,038
93.07 65,104 50,677
93.08 67,370 51,340
93.09 69,637 52,025
93.10 71,903 52,732
93.11 74,169 53,463
93.12 76,436 54,216
93.13 78,702 54,991
93.14 80,968 55,790
93.15 83,235 56,611
93.16 85,501 57,455
93.17 87,767 58,321
93.18 90,034 59,210
93.19 92,300 60,122
93.20 94,566 61,056
93.21 96,833 62,013
93.22 99,099 62,993
93.23 101,365 63,995
93.24 103,631 65,020
93.25 105,898 66,067
93.26 108,164 67,138
93.27 110,430 68,231
93.28 112,697 69,346
93.29 114,963 70,485
93.30 117,229 71,646
Elevation
(feet)
Surface
(sq-ft)
Storage
(cubic-feet)
93.31 119,496 72,829
93.32 121,762 74,036
93.33 124,028 75,265
93.34 126,295 76,516
93.35 128,561 77,790
93.36 130,827 79,087
93.37 133,093 80,407
93.38 135,360 81,749
93.39 137,626 83,114
93.40 139,892 84,502
93.41 142,159 85,912
93.42 144,425 87,345
93.43 146,691 88,800
93.44 148,958 90,279
93.45 151,224 91,780
93.46 153,490 93,303
93.47 155,757 94,849
93.48 158,023 96,418
93.49 160,289 98,010
93.50 162,556 99,624
93.51 164,822 101,261
93.52 167,088 102,921
93.53 169,354 104,603
93.54 171,621 106,308
93.55 173,887 108,035
93.56 176,153 109,785
93.57 178,420 111,558
93.58 180,686 113,354
93.59 182,952 115,172
93.60 185,219 117,013
93.61 187,485 118,876
93.62 189,751 120,763
93.63 192,018 122,671
93.64 194,284 124,603
93.65 196,550 126,557
93.66 198,816 128,534
93.67 201,083 130,533
93.68 203,349 132,556
93.69 205,615 134,600
93.70 207,882 136,668
93.71 210,148 138,758
93.72 212,414 140,871
93.73 214,681 143,006
93.74 216,947 145,164
93.75 219,213 147,345
93.76 221,480 149,549
93.77 223,746 151,775
93.78 226,012 154,024
93.79 228,278 156,295
93.80 230,545 158,589
93.81 232,811 160,906
93.82 235,077 163,245
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Stage-Area-Storage for Pond 10P: South Pond 221S (continued)
Elevation
(feet)
Surface
(sq-ft)
Storage
(cubic-feet)
93.83 237,344 165,607
93.84 239,610 167,992
93.85 241,876 170,400
93.86 244,143 172,830
93.87 246,409 175,283
93.88 248,675 177,758
93.89 250,942 180,256
93.90 253,208 182,777
93.91 255,474 185,320
93.92 257,741 187,886
93.93 260,007 190,475
93.94 262,273 193,086
93.95 264,539 195,720
93.96 266,806 198,377
93.97 269,072 201,057
93.98 271,338 203,759
93.99 273,605 206,483
94.00 275,871 209,231
94.01 275,871 209,231
94.02 275,871 209,231
94.03 275,871 209,231
94.04 275,871 209,231
94.05 275,871 209,231
94.06 275,871 209,231
94.07 275,871 209,231
94.08 275,871 209,231
94.09 275,871 209,231
94.10 275,871 209,231
94.11 275,871 209,231
94.12 275,871 209,231
94.13 275,871 209,231
94.14 275,871 209,231
94.15 275,871 209,231
94.16 275,871 209,231
94.17 275,871 209,231
94.18 275,871 209,231
94.19 275,871 209,231
94.20 275,871 209,231
94.21 275,871 209,231
94.22 275,871 209,231
94.23 275,871 209,231
94.24 275,871 209,231
94.25 275,871 209,231
94.26 275,871 209,231
94.27 275,871 209,231
94.28 275,871 209,231
94.29 275,871 209,231
94.30 275,871 209,231
94.31 275,871 209,231
94.32 275,871 209,231
94.33 275,871 209,231
94.34 275,871 209,231
Elevation
(feet)
Surface
(sq-ft)
Storage
(cubic-feet)
94.35 275,871 209,231
94.36 275,871 209,231
94.37 275,871 209,231
94.38 275,871 209,231
94.39 275,871 209,231
94.40 275,871 209,231
94.41 275,871 209,231
94.42 275,871 209,231
94.43 275,871 209,231
94.44 275,871 209,231
94.45 275,871 209,231
94.46 275,871 209,231
94.47 275,871 209,231
94.48 275,871 209,231
94.49 275,871 209,231
94.50 275,871 209,231
Type II 24-hr 1-yr Rainfall=3.03"Cumberland Proposed Watersheds
Printed 8/29/2018Prepared by S&ME, Inc.
HydroCAD® 10.00-21 s/n 06707 © 2018 HydroCAD Software Solutions LLC
Stage-Area-Storage for Pond 4P: North Pond 222S
Elevation
(feet)
Surface
(sq-ft)
Storage
(cubic-feet)
91.75 9,466 0
91.80 9,913 484
91.85 10,359 991
91.90 10,806 1,520
91.95 11,252 2,072
92.00 11,699 2,646
92.05 12,963 3,262
92.10 14,227 3,942
92.15 15,490 4,685
92.20 16,754 5,491
92.25 18,018 6,360
92.30 19,282 7,293
92.35 20,546 8,288
92.40 21,809 9,347
92.45 23,073 10,469
92.50 24,337 11,655
92.55 25,601 12,903
92.60 26,865 14,215
92.65 28,128 15,590
92.70 29,392 17,028
92.75 30,656 18,529
92.80 31,920 20,093
92.85 33,184 21,721
92.90 34,447 23,412
92.95 35,711 25,165
93.00 36,975 26,983
93.05 40,637 28,923
93.10 44,300 31,046
93.15 47,962 33,353
93.20 51,624 35,843
93.25 55,287 38,515
93.30 58,949 41,371
93.35 62,611 44,410
93.40 66,273 47,632
93.45 69,936 51,038
93.50 73,598 54,626
93.55 77,260 58,397
93.60 80,923 62,352
93.65 84,585 66,490
93.70 88,247 70,810
93.75 91,910 75,314
93.80 95,572 80,001
93.85 99,234 84,871
93.90 102,896 89,925
93.95 106,559 95,161
94.00 110,221 100,581
94.05 116,066 106,238
94.10 121,912 112,187
94.15 127,757 118,429
94.20 133,602 124,963
94.25 139,448 131,789
94.30 145,293 138,908
Elevation
(feet)
Surface
(sq-ft)
Storage
(cubic-feet)
94.35 151,138 146,318
94.40 156,984 154,022
94.45 162,829 162,017
94.50 168,674 170,304
94.55 174,520 178,884
94.60 180,365 187,756
94.65 186,210 196,921
94.70 192,055 206,377
94.75 197,901 216,126
94.80 203,746 226,167
94.85 209,591 236,501
94.90 215,437 247,127
94.95 221,282 258,045
95.00 227,127 269,255
95.05 232,973 280,757
95.10 238,818 292,552

REFERENCE 5

Watersheds, S&ME Inc., August 2018.

© 2018 Microsoft Corporation © 2018 DigitalGlobe ©CNES (2018) Distribution Airbus DS DRAWING PATH: Q:\7235\17\008 Dominion - ACP Contractor Yards\sy10A\SME EXISTING SITE.dwgDRAWING NUMBER
PROJECT NUMBER BYDESCRIPTIONDATENO.CHKAPV9751 SOUTHERN PINE BLVD
CHARLOTTE, NC 28273
[phone]
ENGINEERING FIRM
LICENSE NUMBER: F-0176
PROPOSED CONTRACTOR YARD (SPREAD 10)CUMBERLAND, NORTH CAROLINA7235-17-008
1 2EXISTING WATERSHEDSWATERSHED 121S
WATERSHED 124S
WATERSHED 123S
WATERSHED 122S
Feet
2001000
LEGEND
LIMIT OF CONSTRUCTION
EXISTING COUNTOURS
WATERSHED BOUNDARY
SHEET FLOW
SHALLOW CONCENTRATED FLOW
© 2018 Microsoft Corporation © 2018 DigitalGlobe ©CNES (2018) Distribution Airbus DS
E Q U I P M E N T
STOR
A
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E

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I
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FUEL

T
A
N
K
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939392949294
929494949293E Q U I P M E N T
TRAI
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E
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V

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A

D
MARTHA L HAIR &
KATHY RADCLIFF
PARCEL 0457-51-1976
(1.7 ACRES)
GRAVEL
PARKING LOT
(12.3 ACRES)
GRAVEL
PARKING LOT
(3.2 ACRES)
GRAVEL
PARKING
LOT
(3.2 ACRES)
TOPSOIL
SEGREGATION
(1.0 ACRES)
TOPSOIL
SEGREGATION
(2.9 ACRES)DRAWING PATH: \\charnc\caddata\7235\17\008 Dominion - ACP Contractor Yards\sy10A\SME PROPOSED SITE.dwgDRAWING NUMBER
PROJECT NUMBER BYDESCRIPTIONDATENO.CHKAPV9751 SOUTHERN PINE BLVD
CHARLOTTE, NC 28273
[phone]
ENGINEERING FIRM
LICENSE NUMBER: F-0176
Feet
2001000
LEGEND
LIMIT OF CONSTRUCTION
EXISTING COUNTOURS
WATERSHED BOUNDARY
SHEET FLOW
SHALLOW CONCENTRATED FLOW
CHANNEL FLOW
PIPE FLOW PROPOSED CONTRACTOR YARD (SPREAD 10)CUMBERLAND, NORTH CAROLINA7235-17-008
2 2PROPOSED WATERSHEDSWATERSHED 222S
WATERSHED 221S

REFERENCE 6

Stormwater Design Manual, Part C-0, NCDEQ, Revised January 3,
2017.
NCDEQ Stormwater BMP Manual

________________________________________________________________________________________________________
C-0. MDC for all SCMs 1 Revised: 1-3-2017

C-0. Minimum Design Criteria for all SCMs

Design Objective
This chapter contains Minimum Design Criteria (MDC) that apply to all Stormwater Control Measures
(SCMs). These MDC will apply to each and every SCM that is planned for the project. Additional
MDC will be required depending on the specific type of SCM being proposed. See Part C of this
Manual for SCM-specific requirements.

Important Links
Rule 15A NCAC 2H .1050. MDC for All Stormwater Control Measures

NCDEQ Stormwater BMP Manual

________________________________________________________________________________________________________
C-0. MDC for all SCMs 2 Revised: 1-3-2017

GENERAL MDC 1. SIZING.
The design volume of SCMs shall take into account the runoff at build out from all surfaces
draining to the system. Drainage from off-site areas may be bypassed. The combined
design volume of all SCMs on the project shall be sufficient to handle the required storm
depth.
See Part B of this Manual for information on how to calculate the volume of stormwater runoff.
The required storm depth may vary depending on which stormwater program is applicable to a
given project. The specific required storm depth is provided in each of the program rules. For
example, Rule 15A NCAC 02H .1021(6) requires that for projects designed to achieve runoff
treatment, the required storm depth is one inch for non-coastal HQW and ORW management
zones.

GENERAL MDC 2: CONTAMINATED SOILS.
SCMs that allow stormwater to infiltrate shall not be located on or in areas with contaminated
soils.
Some SCMs that allow water to infiltrate include: infiltration systems, bioretention cells,
permeable pavement, and depending upon native soils, vegetated swales, level spreader-filter
strips, and berms.
Information on contaminated soils can be found at:
 NC DEQ Division of Waste Management Brownfields Program:
http://deq.nc.gov/about/divisions/waste-management/brownfields-program
 US EPA Brownfields: https://www.epa.gov/brownfields

GENERAL MDC 3: SIDE SLOPES.
Side slopes of SCMs stabilized with vegetated cover shall be no steeper than 3:1 (horizontal
to vertical). Retaining walls, gabion walls, and other engineered surfaces may be steeper
than 3:1. Steeper vegetated slopes may be considered on a case-by-case basis if the
applicant demonstrates that the soils and vegetation shall remain stable.
When steeper vegetated slopes are proposed, the applicant should take into account safety and
ease of maintenance. Establishing vegetation is more difficult on steep slopes. The applicant
should be able to demonstrate that suitable vegetation will be chosen and that they have a plan
for maintaining the vegetation. Erosion control structures may need to be used in combination
with vegetation on steep slopes.

NCDEQ Stormwater BMP Manual

________________________________________________________________________________________________________
C-0. MDC for all SCMs 3 Revised: 1-3-2017

GENERAL MDC 4: EROSION PROTECTION.
The inlets SCMs shall be designed to protect the SCM from erosion resulting from
stormwater discharges. The outlets of SCMs shall be designed so that they do not cause
erosion immediately downslope of the discharge point during the peak flow from the 10-year
storm event as shown by engineering calculations.
Guidance on inlet and outlet protection can be found in Chapter 6, Section V. Outlet Protection
& VI Inlet Protection of the NC Erosion and Sediment Control Planning and Design Manual:
http://deq.nc.gov/about/divisions/energy-mineral-land-resources/energy-mineral-land-permit-
guidance/erosion-sediment-control-planning-design-manual

GENERAL MDC 5: EXCESS FLOWS.
SCMs shall include an overflow or bypass device for inflow volumes in excess of the
treatment volume, or, if applicable, the peak attenuation volume.
Recommend checking with county or municipality concerning local flood control or stormwater
quantity control requirements.

GENERAL MDC 6: DEWATERING.
SCMs shall have a method to draw down any standing water to facilitate maintenance and
inspection.
Recommend pumping down wet ponds and wetlands rather than using a drawdown orifice at
the invert to avoid discharging sediment.

GENERAL MDC 7: CLEAN OUT AFTER CONSTRUCTION.
Every SCM impacted by sedimentation and erosion control during the construction phase
shall be cleaned out and converted to its approved design state.
Recommend having installed SCM’s inspected and cleaned after each heavy rainfall in addition
to inspection at the completion of the construction phase. Additional recommendations for
Construction are contained in Part A of this Manual.

NCDEQ Stormwater BMP Manual

________________________________________________________________________________________________________
C-0. MDC for all SCMs 4 Revised: 1-3-2017

GENERAL MDC 8: MAINTENANCE ACCESS.
Every SCM installed pursuant to this Section shall be made accessible for maintenance and
repair. Maintenance accesses shall:
(a) have a minimum width of ten feet;
(b) not include lateral or incline slopes that exceed 3:1 (horizontal to vertical); and
(c) extend to the nearest public right-of-way.
For SCMs that may require the use of large equipment for maintenance, such as wet ponds, a
width of 25 feet is recommended for maintenance access. Direct maintenance access to the
forebay should be provided for SCMs which utilize a forebay. Access for cleaning underdrain
piping should be provided for SCMs which utilize underdrains.

GENERAL MDC 9: EASEMENTS.
All SCMs and associated maintenance accesses on privately owned land except for those
located on single family residential lots shall be located in permanent recorded easements.
The SCM shall be shown and labeled within the easement. These easements shall be
granted in favor of the party responsible for enforcing the stormwater program under which
the SCMs were approved.
SCMs must have access and maintenance easements to provide the legal authority for
inspections, maintenance personnel and equipment. The location and configuration of
easements must be established during the design phase and should be clearly shown on the
design drawings. The entire footprint of the SCM system must be included in the access and
maintenance easement, plus an additional ten or more feet around the SCM to provide enough
room to complete maintenance tasks. This SCM system includes the side slopes, forebay, riser
structure, SCM device, and basin outlet, dam embankment, outlet, and emergency spillway.
In addition to the provisions required by Rule, it is recommended that maintenance easements
specify who may make use of the easement and for what purposes. Where feasible, it is also
recommended that SCMs be posted with conspicuous signage stating who is responsible for
required maintenance and annual inspection. Signage should be maintained so as to remain
visible and legible.
GENERAL MDC 10: SINGLE FAMILY RESIDENTIAL LOTS.
Plats for residential lots that contain an SCM shall include:
(a) the specific location of the SCM on the lot;
(b) a typical detail for SCM to be used; and
(c) a note that the SCM on the property has been required to meet stormwater regulations
and that the property owner may be subject to enforcement actions if the SCM is removed,
relocated, or altered without prior approval.
DEQ recommends including, specific maintenance requirements/schedule for lots containing an
SCM on the plat. The owner should maintain a copy of maintenance requirements and a log of
maintenance activities that indicates the dates of each maintenance visit and the specific
activities that were performed on those dates. Additional recommendations for Single Family
Residential Lots are contained in Part E of this Manual.
NCDEQ Stormwater BMP Manual

________________________________________________________________________________________________________
C-0. MDC for all SCMs 5 Revised: 1-3-2017

GENERAL MDC 11: OPERATION AND MAINTENANCE AGREEMENT.
The owner of the SCMs shall enter into a binding Operation and Maintenance (O&M)
Agreement with the party responsible for implementing the stormwater program under which
the SCMs were approved. The O&M Agreement shall require the owner to maintain, repair,
or reconstruct the SCMs in accordance with the approved design plans and the O&M Plan.
The O&M Agreement shall be referenced on the final plat and shall be recorded with the
county Register of Deeds upon final plat approval. If no subdivision plat is recorded for the
site, then the O&M Agreement shall be recorded with the county Register of Deeds so as to
appear in the chain of title of all subsequent purchasers.
It is recommended that the O&M agreement require the owner or owners of the SCM to grant a
right of entry in the event that the state or local permitting authority has reason to believe it has
become necessary to inspect, monitor, maintain, repair or reconstruct the SCM. In no case
shall the right of entry, of itself, confer an obligation on the state or local permitting authority to
assume responsibility for the SCM.
Where SCMs are to be owned and maintained by a homeowners’ association, property owners’
association, or similar entity, it is recommended that the O&M agreement include the following
provisions:
(a) an acknowledgement that the association shall continuously operate and maintain the
stormwater control and management facilities; and
(b) establishment of an escrow account which can be spent solely for sediment removal,
structural, biological or vegetative replacement, major repair, or construction of the SCM;
Additional recommendations for O&M agreements are contained in Part A of this Manual.

GENERAL MDC 12: OPERATION AND MAINTENANCE PLAN.
There shall be an O&M Plan for every project subject to this Rule. The O&M Plan shall
specify all operation and maintenance work necessary for the function of all SCM
components, including the stormwater conveyance system, perimeter of the device, inlet(s),
pretreatment measures, main treatment area, outlet, vegetation, and discharge point. The
O&M plan shall specify methods to be used to maintain or restore the SCMs to design
specifications in the event of failure. O&M plans shall be signed by the owner and notarized.
The owner shall keep maintenance records and these shall be available upon request by the
party responsible for enforcing the stormwater program under which the SCMs were
approved.
The long-term effectiveness of any structural BMP relies, above all, on appropriate
maintenance. It is recommended that you use the O&M EZ form to create one O&M agreement
for an entire site. For your convenience, only the cover page has to be signed and notarized.
Additional recommendations for O&M plans are contained in Part A of this Manual.

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GENERAL MDC 13: SCM SPECIFIC MINIMUM DESIGN CRITERIA (MDC).
Every SCM shall follow the applicable device specific MDC pursuant to Rules .1051 through
.1062 of this Section.
It is recommended that you use the Supplement-EZ form to create one master supplement form
for the entire project. The Supplement-EZ form has been updated to reflect the new general
MDC and SCM-specific MDC. Additional recommendations for SCM-specific MDC is contained
in Part C of this Manual.

GENERAL MDC 14: SCM DESIGNER QUALIFICATIONS FOR THE FAST-TRACK
PERMITTING PROCESS.
For the fast-track permitting process as set forth in Rules .1043 and .1044 of this Section,
SCMs and components of SCMs shall be designed by persons licensed under Chapters
89A, 89C, 89E, or 89F of the General Statutes.
NCGS 89A Landscape Architects:
http://www.ncleg.net/enactedlegislation/statutes/pdf/bychapter/chapter_89a.pdf
NCGS 89C Engineering and Land Surveying:
http://www.ncleg.net/enactedlegislation/statutes/html/bychapter/chapter_89c.html
NCGS 89E Geologists Licensing Act:
http://www.ncleg.net/enactedlegislation/statutes/html/bychapter/chapter_89e.html
NCGS 89F North Carolina Soil Scientist Licensing Act:
http://www.ncga.state.nc.us/EnactedLegislation/Statutes/PDF/ByChapter/Chapter_89F.pdf

GENERAL MDC 15: NEW STORMWATER TECHNOLOGIES.
Applicants shall have the option to request Division approval of new stormwater technologies
and associated MDC. Division approval shall be based on engineering calculations and
research studies demonstrating that the new technology functions in perpetuity and is
equally or more protective of water quality than the requirements of this Section.
Refer to Part F of this Manual for additional guidance on requesting approval of new stormwater
technologies.

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GENERAL MDC 16: NO EXCEPTIONS TO UNAUTHORIZED PROFESSIONAL
PRACTICE.
This Rule creates no exceptions to the unauthorized practice of the professions described in
Chapters 89A, 89C, 89E, or 89F, or the rules, standards, or codes of professional conduct
promulgated by the applicable professional licensing boards.
Licensed professionals designing stormwater control systems and components of stormwater
control systems must adhere to the general statutes under which they are licensed. This
includes following the applicable Code of Professional Conduct adopted by the governing
licensing board. Requirements for affixing professional seals on soils reports, hydrogeologic
evaluations, landscaping plans, engineering plans, and other documents involved in the practice
of a licensed profession as required by the applicable governing licensing board must be
followed. The permitting authority may request proof of licensure from applicants engaging in
these types of professional activities.

REFERENCE 7

Stormwater Design Manual, Part C-4, NCDEQ, Revised January 19,
2018.

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C-4. Stormwater Wetland

Design Objective
Stormwater wetlands are constructed systems that mimic the functions of natural wetlands and
use physical, chemical, and biological processes to treat stormwater. A stormwater wetland is
designed to capture the design storm and release it slowly over a period of two to five days via a
properly designed outlet structure. The wetland shall be designed in a manner that protects the
device, the areas around the device and the receiving stream from erosion. Stormwater wetlands
temporarily store stormwater runoff in shallow pools that support emergent and riparian
vegetation. The storage, complex microtopography, and vegetative community in stormwater
wetlands combine to form an ideal matrix for the removal of many pollutants. Stormwater
wetlands can also effectively reduce peak runoff rates and stabilize flow to adjacent natural
wetlands and streams.

Design Volume
The design volume for a wetland is the volume that can be retained for a two to five-day period
between the temporary pool elevation and the permanent pool elevation.

Important Links
Rule 15A NCAC 2H .1054. MDC for Stormwater Wetlands
SCM Credit Document, C-4. Credit for Stormwater Wetlands

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Table of Contents
Guidance on the MDC
MDC 1: Temporary Ponding Depth
MDC 2: Peak Attenuation Depth
MDC 3: Surface Area
MDC 4: Soil Amendments
MDC 5: Location of Inlet(s) and Outlet
MDC 6: Forebay
MDC 7: Non-forebay Deep Pools
MDC 8: Shallow Water Zone
MDC 9: Temporary Inundation Zone
MDC 10: Drawdown Time
MDC 11: Protection of the Receiving Stream
MDC 12: Landscaping Plan
MDC 13: Shallow Water Plantings
MDC 14: Temporary Inundation Zone Plantings
MDC 15: Dam Structure and Perimeter Fill Slopes
MDC 16: No Cattails
MDC 17: Trash Rack

Recommendations
Recommendation 1: Sufficiently Large Drainage Area
Recommendation 2: Deep Zone Plantings

Construction

Maintenance

Comparison of Old Versus New Design Standards

References

Photo Gallery

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Figure 1: Stormwater Wetland Example - Plan View

Figure 2: Stormwater Wetland Example – Schematic Cross-Section

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Figure 3: Stormwater Wetland Example - Riser

Guidance on the MDC
Guidance on MDC
MDC 1
WETLAND MDC 1. TEMPORARY PONDING DEPTH.
The ponding depth for the design volume shall be a maximum of 15 inches above the
permanent pool.
The temporary ponding depth for the design volume may not exceed 15 inches in order to
protect the health of the plants and the integrity of the soils.

An adjustable outlet device is highly recommended. Adjustable outlet devices allow the
owner/operator of the stormwater wetland to easily correct any construction errors in the
wetland depth. In addition, an adjustable outlet device allows the owner/operator to hold the
ponding depth to a lower level (no less than four inches) during the first growing season to allow
the plants to become established. This practice increases the survivability of the plants.
However, the outlet must be brought up to the design ponding depth within the first year after
construction to ensure that the entire design storm is treated. Restoring the ponding depth must
be in the construction contract and the responsible person must be named. Figure 5 shows two
examples of adjustable outlet structures in a stormwater wetland.
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Figure 4: Two Examples of Adjustable Outlets

MDC 2
WETLAND MDC 2. PEAK ATTENUATION DEPTH.
The wetland may be designed to temporarily pond peak attenuation volume at a depth
exceeding 15 inches.
Additional depth may be provided for peak attenuation; a storm size is not specified, that may
be determined by the applicant and will likely be based on local peak attenuation requirements.
MDC 3
WETLAND MDC 3. SURFACE AREA.
The surface area shall be sufficient to limit the ponding depth to 15 inches or less. The
surface area specifications in Wetland MDC (6) through (9) are based on the wetland at its
temporary ponding depth.
The minimum wetland surface area at temporary pool shall be determined by dividing the
design volume in cubic feet by 1.25 feet (the maximum allowed ponding depth for the temporary
pool). The designer may make the wetland larger (with a shallower ponding depth).
MDC 4
WETLAND MDC 4. SOIL AMENDMENTS.
The pH, compaction, and other attributes of the first 12-inch depth of the soil shall be adjusted
if necessary to promote plant establishment and growth.
A soil analysis should be conducted within the stormwater wetland to determine the viability of
soils for healthy vegetation growth. Imported or in-situ soils may be amended with organic
material, depending on soil analysis results, to enhance suitability as a planting media. More
guidance on soil amendments can be found in Part A-2 of this manual. Native plants grown in
topsoil typically do not need fertilization or lime.
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MDC 5
WETLAND MDC 5. LOCATION OF INLET(S) AND OUTLET.
The inlet(s) and outlet shall be located in a manner that avoids short circuiting.
Stormwater wetlands shall be designed in manner that maximizes the flow path from the inlet or
inlets to the outlet. This allows for sufficient contact time for pollutant removal. Figure 1 at the
beginning of this chapter shows how the flow path can be enhanced with additional sinuosity by
proper grading. Figure 11 on page 25 also shows a good example of extending the flow path.
MDC 6
WETLAND MDC 6. FOREBAY.
A forebay shall be provided at the inlet to the stormwater wetland. The forebay shall
comprise 10 to 15 percent of the wetland surface area. The forebay depth shall be 24 to 40
inches below the permanent pool elevation. The forebay entrance shall be deeper than the
forebay exit. If sediment accumulates in the forebay in a manner that reduces its depth to 15
inches, then the forebay shall be cleaned out and returned to its design state.
The forebay is a deep pool down flow of the inlet to ease maintenance of the stormwater
wetland. Making the forebay entrance deeper than the exit increases its effectiveness at
dissipating energy and settling solids. Deep pools are best colonized by plants with submerged
roots. Deep pools slow flow velocities and trap sediment, absorb nutrients in the water column,
improve oxidation, and create habitat for wildlife and mosquito predators such as frogs, fish, and
dragonfly nymphs during dry times.
MDC 7
WETLAND MDC 7. NON-FOREBAY DEEP POOLS.
Deep pools shall be provided throughout the wetland and adjacent to the outlet structure to
prevent clogging. The non-forebay deep pools shall comprise 5 to 15 percent of the wetland
surface area and shall be designed to retain water between storm events. The deep pools
at their deepest points shall be at least 18 inches below the permanent pool elevation.
Stormwater wetlands should be designed with
non-forebay deep pools that retain some water.
These pools provide habitat for gambusia fish
and other predators (Figure 5), which prey upon
mosquito larvae. Submerged and floating plants
may be used in this area, except around the
wetland outlet device. The deep pool at the
outlet should be non-vegetated to prevent
clogging. Deep pools in A or B soils should be
lined to ensure that they don’t infiltrate and stay
wet between storm events.
Figure 5: Gambusia fish

Site soils and groundwater elevation strongly influence the way stormwater wetlands should be
constructed and their ultimate success or failure. A soils report with a determination of the
seasonal high water table (SHWT) and in-situ soil permeability should be prepared. If the
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SHWT is not located near ground surface and the wetland will be located in A or B soils, a clay
or geomembrane liner should be installed in the deep pools and shallow water areas to sustain
the permanent pool of water. Figure 6 shows a stormwater wetland in Garner, NC that has
been negatively impacted by infiltration.

Figure 6: Stormwater Wetland Impacted by Infiltration

MDC 8
WETLAND MDC 8. SHALLOW WATER ZONE.
The shallow water zone shall comprise 35 to 45 percent of the wetland surface area. The
shallow water zone shall be zero to nine inches below the permanent pool elevation.
Shallow water includes all areas inundated by the permanent pool to a depth of zero to nine
inches with occasional drying during periods of drought. The shallow water zone provides a
constant hydraulic connection between the inlet and outlet structure of the stormwater wetland.
The top of the shallow water zone represents the top of the permanent pool elevation.
MDC 9
WETLAND MDC 9. TEMPORARY INUNDATION ZONE.
The temporary inundation zone shall comprise 30 to 45 percent of the wetland surface area.
The temporary inundation zone shall be between 0 and 15 inches above the permanent pool
elevation.
The temporary inundation zone holds water only after rain events, and rooted plants live in this
zone. The plants and soils in the temporary inundation zone remove pollutants via filtering and
biological processes and provide shade for the stormwater wetland. Plants should be carefully
selected for this zone to ensure survival during both wet and dry conditions. Soil bioengineering
techniques, such as the use of fascines, stumps or logs, and coconut fiber rolls, can be used to
create and reinforce the temporary inundation zone in areas of the stormwater wetland that may
be subject to high flow velocities.
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MDC 10
WETLAND MDC 10. DRAWDOWN TIME.
The design volume shall draw down to the permanent pool level between two and five days.
Besides drawing the design volume down in two to five days, the outlet in a stormwater wetland
should be accessible to operators and resistant to clogging. In addition, the outlet structure
shall have a bypass structure for larger storm events, and may, if the applicant so chooses, be
designed to attenuate peak flows. The orifice may also include manual drawdown valves or
flashboard risers (also called sliding weir plates) so that maintenance personnel can drain the
wetland for maintenance purposes. If installed, drawdown valves should be secured so that
only intended personnel can access them.
It is also recommended that the outlet structure be easily adjusted to allow the owner/operator
to correct water levels as needed. Water levels may need to be lowered during and following
plant installation.
Figure 7 shows the drawdown orifice, the overflow for larger storm events, and a manually
operated valve for maintenance. One method to prevent clogging in the drawdown orifice is to
turn the orifice downward below the normal pool. This prevents floating debris or vegetation
from clogging the orifice.

If the wetland is in trout-sensitive waters,
consider extending the orifice to close to the
bottom of the drawdown structure among a pile
of riprap. This will ensure that cooler water
enters the stream to protect trout.

The overflow structure should be located near
the edge of the wetland so that it can be
accessed easily for maintenance. Overflow
structures that are several feet into the wetland
are difficult to reach and likely will not be
maintained. See Figure 8.

Figure 7: Outlet Structure

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Figure 8: How to Plan for Outlet Structure Maintenance
YES

NO

MDC 11
WETLAND MDC 11. PROTECTION OF THE RECEIVING STREAM.
The wetland shall discharge the runoff from the one-year, 24-hour storm in a manner that
minimizes hydrologic impacts to the receiving channel.
Eventually, there will be more technical information available on this MDC. For now, it is being
researched at NCSU.

MDC 12
WETLAND MDC 12. LANDSCAPING PLAN.
A landscape plan prepared by a licensed professional shall be provided and shall include the
following:
(a) delineation of planting zones;
(b) plant layout with species names and locations; and
(c) total number and sizes of all plant species.
Plants improve water quality by slowing velocity, which settles solids. Plants also supply carbon
sources and habitat for microbes that decompose organic compounds and convert significant
quantities of nitrate directly to nitrogen gas. Many herbaceous wetland plants die back during
the winter. This creates a dense layer of plant litter that also provides a substrate that traps
solids and supports microbial growth.

For these reasons, planning and maintaining the health of the stormwater wetland plants is
crucial. See Figure 9 for a summary of the how plants, microbes and soil contribute to the
function of stormwater wetlands. Having a dense stand of healthy plants is more important to
wetland functioning than the specific plant species that are present, as long as they are
ecologically appropriate. The best species are native, non-invasive plants with high colonization
and growth rates. Species that will persist structurally through the winter are an important
consideration. Examples include woody shrubs and some sedges and rushes. In addition, the
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plant should be robust in periodically flooded environments that may dry out during periods of
drought.

Figure 9: Stormwater Wetland Microbes, Plants, and Soil

The landscaping plan should be prepared by a qualified design professional licensed in North
Carolina should include the following:
(a) delineation of planting zones (required);
(b) total quantity of plants needed, a list of species that would be acceptable in each
planting zone (see Tables 1-3), and minimum number of distinct species to be installed
in each planting zone (required);
(c) species used in SCMs should be, at a minimum, native to NC and grown in a nursery
located in NC or within 200 miles of the SCM. In addition, it is preferable for the plants
to be grown from seed collected within NC or contiguous states.
(d) minimum size requirements for plants (required);
(e) at least two sources for the plant material, from within the project’s ecoregion;
(f) sequence and timing for preparing wetland bed (including soil amendments, initial
fertilization, and watering, as needed); and
(g) specification of supplementary plantings to replenish losses.

At a minimum, species utilized in stormwater wetlands should be:
• Native to the ecoregion of the wetland being constructed and sourced from a nursery
no further south than USDA Hardiness Zone 8b to ensure greater survivability of the
planting;
• Straight species, rather than cultivated varieties of native plants; and
• Adapted to the water level zone into which they will be installed.
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MDC 13
WETLAND MDC 13. SHALLOW WATER PLANTINGS.
The shallow water zone shall be planted at a minimum density of 50 herbaceous plants per
200 square feet (equivalent to 2 foot on center spacing).
The shallow water zone includes all areas that are inundated by the normal pool to a depth up
to 9 inches. This zone does become drier during periods of drought. Shallow water zones, such
as littoral shelves should be vegetated with emergent plants and provide some of the best
treatment zones in the wetland.
Another way to think of this MDC is that it is equivalent to one plant per every 4 square feet.
However, wetland plants are most likely to survive if planted in the shallowest 0-6” of the
shallow water zone. Therefore, DEQ encourages concentrating the plant coverage in the
shallowest 0-6” at a higher density to achieve an average density across the shallow water zone
of one plant per 4 square feet.

In addition to plant density, the designer should also consider the following when designing
shallow water plantings:
• HITTING THE DEPTH CORRECTLY. It is very important to hit the required 0-9” depth
for the shallow water zone correctly because plants installed there will not survive if the
soils are dry or if the plants are covered by more than 9” of water.
• NUMBER OF PLANT SPECIES. At least six different species of plants should be
installed in the stormwater wetland. A greater diversity of plant species will increase the
resilience of the wetland to changing environmental conditions.
• CONTAINER SIZE. In most cases, plants installed in stormwater wetlands are grown in
containers holding 3.6 to 6.8 cubic inches of media (for example, and not limited to, 72,
50 and IP 110). Other container sizes or bare root stock may be appropriate for some
species and conditions.
• PLANT HEIGHT. Plants that grow in shallow water (water’s edge to 6” below normal
water level) must have at least 3” of above-water foliage when installed. This can be
achieved by adjusting the water level of the wetland to accommodate plans with shorter
foliage or by specifying that plants must have at least a 9” foliage height when installed
in this zone.
• TIMING OF INSTALLATION. Installation is generally considered safe from the average
last spring frost for the wetland location until several weeks before the average first fall
frost for the wetland location. It is difficult to guarantee survivability for herbaceous
plants installed during the dormant season.

The plant species listed in Tables 1-3 below have performed well in NC stormwater wetlands
and can be reliably propagated in wetland plant nurseries. These lists are not exhaustive.
Personal experience, many excellent publications, and recommendations from wetland
scientists, landscape architects, and wetland plant growers may reveal additional useful
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species. The icons denote if the species provide a food source for butterflies/moths (), bees
() and birds ().

Table 1: Plants for Shallow Water Zone
Botanical Name Common Name Ideal
Depth
Notes
Acorus americanus Sweetflag 0-2”
Canna flaccida Yellow canna 0-2”
Dulichium arundinaceum Three-way sedge 0-6
Eleocharis acicularis
and
Eleocharis quadrangulata
Needle spikerush
and
Squarestem spikerush
0-9”

1-12
.

Iris virginica Virginia iris 0-2”

Juncus effusus Common rush 0-2”

Lilaeopsis carolinensis
and
Lilaeopsis chinensis
Carolina grasswort
and
Eastern grasswort
0-9” Several inches tall, native only to
coastal plain.

Nelumbo lutea American lotus 1”-3’ Robust water-lily type that will spread.

Nuphar lutea ssp. advena Yellow pond-lily

1”-3’ A water-lily type species that will
spread.

Nymphaea odorata American white waterlily 1”-3” A water-lily that will spread.

Orontium aquaticum Golden club 0-6”
Peltandra virginica Arrow arum -0-12” Spreads vigorously.

Pontederia cordata Pickerelweed 0-12” Spreads vigorously.

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Sagittaria latifolia Broadleaf arrowhead 0-6” Spreads vigorously.

Sagittaria lancifolia Bulltongue arrowhead 2-6” Native only to coastal plain. Spreads
vigorously.

Saururus cernuus Lizard’s tail 0-6” Spreads vigorously.

Schoenoplectus americanus
Schoenoplectus pungens
Chairmaker’s bulrush
Common threesquare
0-2” Not native to mountains.

Schoenoplectus
tabernaemontani
Softstem bulrush 0-6” Spreads vigorously.

Scirpus cyperinus
Scirpus expansus
Wool grass
Sedge/Woodland bulrush
0-2”

Sparganium americanum American bur-reed 0-6” Spreads vigorously.

Zizaniopsis miliacea Giant cutgrass 2-6” Not native to mountains. Foliage
present all year.Spreads vigorously.

MDC 14
WETLAND MDC 14. TEMPORARY INUNDATION ZONE PLANTINGS.
The temporary inundation zone shall be planted according to one of the following options:
(a) 50 herbaceous plants per 200 square feet (equivalent to 2-foot on center
spacing);
(b) eight shrubs per 200 square feet (equivalent to 5 foot on center spacing); or
(c) one tree and 40 grass-like herbaceous plants per 100 square feet.
The temporary inundation zone stabilizes the slopes and optimizes pollutant removal during
storm events. Shallow land zones should be planted with wetland vegetation capable of
growing in alternating dry and inundated conditions. The temporary inundation zone should be
planted with vegetation that can withstand irregular inundation and occasional drought.
Table 2: Herbaceous Plants for the Temporary Inundation Zone
Botanical Name Common Name Notes
Andropogon glomeratus Bushy Beardgrass
Bushy Bluestem

Amsonia tabernaemontana Eastern blue star
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Asclepias incarnata Swamp Milkweed Not found in mountains.

Carex amphibola
Carex cherokeensis
Carex crinita
Carex glaucescens
Carex gravi
Carex intumescens
Carex lupulina
Carex lurida
Carex stricta
Carex vulpinoidea
Creek sedge
Cherokee sedge
Fringed Sedge
Southern waxy sedge
Gray’s sedge
Bladder sedge
Hop sedge
Lurid Sedge
Tussock Sedge
Fox Sedge

Chasmanthium latifolium
Chasmanthium laxum
River Oats
Slender woodoats

Chelone glabra White Turtlehead Not found in mountains.

Cladium jamaicense Saw grass
Conoclinium coelestinum Blue Mistflower

Coreopsis lanceolata
Coreopsis tinctoria
Tickseed
Dulichium arundinaceum Three-way sedge
Echinacea purpurea Purple cone flower
Elymus canadensis
Elymus hystrix
Elymus virginicus
Wildrye

Eupatorium perfoliatum Boneset
Eutrochium dubium (syn.
Eupatorium dubium)
Eutrochium fistulosum (syn
Eupatorium fistulosum)
Eutrochium maculatum (syn.
Eupatorium maculatum)
Coastal Joe Pye Weed
Hollow Stemmed Joe Pye
Weed
Spotted Joe Pye Weed

Gallardia pulchella Blanket flower
Helenium autumnale Sneezeweed
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Helianthus angustifolius Swamp Sunflower

Heliopsis hellianthoides False sunflower
Hibiscus coccineus
Hibiscus laevis
Hibiscus moscheutos
Scarlet Rosemallow
Halberldeaf Rosemallow
Marsh Hibiscus
Not found in mountains

Juncus effusus
Juncus coriaceus
Juncus tenuis
Common Rush
Leathery rush
Path Rush
Evergreen

Kosteletskya pentacaropos
(syn. Kosteletskya virginica)
Saltmarsh Mallow Coastal plain only
Liatris spicata Blazing star/Dense blazing
star
Lobelia cardinalis
Lobelia elongata
Cardinal Flower
Blue lobelia
L. elongate not found in mountains

Monarda fistulosa
Monarda didyma
Bee balm
Muhlenbergia capillaris Purple Muhly Not found in mountains, Coastal plain genetic
origin preferred

Panicum rigidulum (syn.
Coleataenia rigidula)
Panicum virgatum
Redtop panicgrass
Switchgrass
Ratibida pinnata Gray-headed coneflower
Rhynchospora colorata Starrush Whitetop
Saururus cernuus Lizard’s tail
Erianthus brevibarbis
(syn. Saccharum brevibarbe)
Erianthus giganteus (syn.
Saccharum giganteum)
Narrow Plume Grass
Sugar Cane Plumegrass

Scirpus atrovirens
Scirpus cyperinus
Green Bulrush
Wool grass

Silphium perfoliatum Cup plant
Solidago canadensis
Solidago rugosa
Solidago sempervirens
Goldenrod
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Syphyotrichum lateriflorum
Syphyotrichum laeva laeve
Syphyotrichum novae-angliae
Syphyotrichum oblongifolium
Calico aster
Smooth aster
New England aster
Aromatic aster

Verbena hastata Swamp Verbena

Vernonia noveboracensis Ironweed

Table 3: Shrubs for the Temporary Inundation Zone
Botanical Name Common Name
Aesculus pavia
Aesculus sylvatica
Red buckeye
Painted buckeye
Alnus serrulata Tag alder/Hazel alder
Amelanchier arborea Downy service-berry
Amelanchier canadensis Canadian serviceberry
Aronia arbutifolia Red Chokeberry

Callicarpa americana Beautyberry
Ceonothus americanus New Jersey tea
Cephalanthus occidentalis Common button bush
Clethra alnifolia Summersweet clethra
Cornus amomum Silky dogwood
Cyrilla racemiflora Swamp cyrilla (ti-ti)
Diospyros virginiana Persimmon
Eubotrys racemosus Fetterbush/Swamp dog hobble
Hamamelis virginiana Witchhazel
Hypericum densiflorum Dense hypericum
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Ilex decidua Possum haw
Ilex glabra Inkberry
Ilex verticillata Winterberry
Ilex vomitoria Yaupon holly
Itea virginica Virginia sweetspire
Lindera benzoin Northern spicebush
Leucothoe fontanesiana
Leucothoe axillaris Highland doghobble
Coastal doghobble
Lyonia lucida Fetterbush
Rhododendron viscosum
Rhododendron atlanticum Swamp azalea
Dwarf azalea
Physocarpus opulifolius Ninebark
Rosa palustris Swamp rose
Salix caroliniana
Salix serica
Carolina willow
Silky willow
Sambucus canadensis
(syn. S. nigra ssp. canadensis)
American black elderberry

Spiraea tomentosa Hardhack/Steeple bush
Styrax americanus American snowbell
Symphoricarpos orbiculatus Coralberry
Vaccinium arboreum
Vaccinium corymobosum corymbosum
Vaccinium fuscatum
Farkleberry
Highbush blueberry
Black highbush blueberry
Viburnum dentatum
Viburnum prunifolium
Viburnum nudum
Arrowwood viburnum
Blackhaw viburnum
Possumhaw viburnum
Xanthorhiza simplicissima Yellowroot

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MDC 15
WETLAND MDC 15. DAM STRUCTURE AND PERIMETER FILL SLOPES.
On the dam structure and perimeter fill slopes, non-clumping turf grass shall be provided,
and trees and woody shrubs shall not be allowed.
The turf areas on the dam structure and perimeter fill slopes should be stabilized within 14 days
after the end of construction. The stabilization might be the final vegetation or a temporary
stabilization measure until the vegetation becomes established.
MDC 16
WETLAND MDC 16. NO CATTAILS.
Cattails shall not be planted in the wetland.
At first glance, cattails, with their long, thick leaves
and their decorative brown seed heads are
interesting and attractive in a stormwater wetland.
However, cattails are very invasive (250,000 seeds
per seed head) and can quickly take over an entire
stormwater wetland, outcompeting other plants and
eventually reducing the storage capacity of the
wetland. Matted cattails detritus also provides
excellent mosquito habitat. The plants in Tables 1-3
above are just as impressive and not invasive.
Figure 10: Cattails
MDC 17
WETLAND MDC 17. TRASH RACK.
A trash rack or other device to trap debris shall be provided on piped outlet structures.
See Part A-3 for more information on how to select a trash rack.
Recommendations
Recommendations
Rec 1
WETLAND RECOMMENDATION 1: SUFFICIENTLY LARGE DRAINAGE AREA
It is recommended to have a drainage area of at least two acres to provide year-round
hydration for wetland plants to grow and thrive.
Stormwater wetlands often thrive better when they have a sufficiently large drainage area (two
acres or more) to provide year-round hydration, particularly when they are installed in A or B
soils. Since water depths are shallower than in wet detention ponds, water loss by evaporation
is an important concern.

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Rec 2
WETLAND RECOMMENDATION 2: DEEP ZONE PLANTINGS.
Deep zone plantings are not required, but the designer may use them if desired for aesthetic
purposes. They may not be planted in the deep zone adjacent to the outlet structure to
prevent clogging.

Table 4: Floating Aquatic Plants for the Deep Zone
Botanical Name Common Name
Nymphaea odorata White water lily
Nelumbo lutea American lotus
Nuphar lutea ssp. advena Yellow Pond-lily

Construction
Construction
Consider construction sequencing so that vegetation can be planted and the wetland brought
online within 14 days. Plants may need to be watered during this time if the device is not
brought online the same day. Stabilization may be in the form of final vegetation plantings or a
temporary means until the vegetation becomes established. A good temporary means of
stabilization is a wet hydroseed mix. For rapid germination, scarify the soil to a half -inch prior to
hydroseeding.

Inlet and outlet channels should be protected from scour that may occur during periods of high
flow. Standard erosion control measures should be used. The Land Quality Section of the North
Carolina Department of Environment and Natural Resources and the U.S. Department of
Agriculture Natural Resource Conservation Service (NRCS) can provide information on erosion
and sediment control techniques.

The stormwater wetland should be staked at the onset of the planting season. Water depths in
the wetland should be measured to confirm the original planting zones. At this time, it may be
necessary to modify the planting plan to reflect altered depths or the availability of wetland plant
stock. Surveyed planting zones should be marked on an “as-built” or record design plan and
located in the field using stakes or flags.

The wetland drain should be fully opened for no more than 3 days prior to the planting date
(which should coincide with the delivery date for the wetland plant stock) to preserve soil
moisture and workability.

The most common and reliable technique for establishing an emergent wetland community in a
stormwater wetland is to transplant nursery stock obtained from local aquatic plant nurseries.
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The optimal period for transplanting extends from early April to mid-June so that the wetland
plants will have a full growing season to build the root reserves needed to survive the winter.
However, some species may be planted successfully in early fall. Contact your nursery well in
advance of construction to ensure that they will have the desired species available.

Post-nursery care of wetland plants is very important in the interval between delivery of the
plants and their subsequent installation because they are prone to desiccation. Stock should be
frequently watered and shaded.

Maintenance

Maintenance

Although wetland plants require water for growth and reproduction, they can be killed by
drowning in excessively deep water. Usually, initial growth is best with transplanted plants in
wet, well-aerated soil. Occasional inundation followed by exposure to air of the majority of the
vegetation enables the plants to obtain oxygen and grow optimally. Conversely, frequent soil
saturation is important for wetland plant survival.

Dramatic shifts can occur as plant succession proceeds. The plant community reflects
management and can indicate problems or the results of improvements. For example, a
requirement of submerged aquatic plants, such as pondweed (Potamogeton spp.), is light
penetration into the water column. The disappearance of these plants may indicate inadequate
water clarity. The appearance of invasive species or development of a monoculture is also a
sign of a problem with the aquatic/soil/vegetative requirements. For instance, many invasive
species can quickly spread and take over a wetland. If cattails become invasive, they can be
removed by a licensed aquatic pesticide applicator by wiping aquatic glyphosate, a systemic
herbicide, on the cattails.

Unlike maintenance requirements for wet or dry stormwater ponds, sediment should only be
selectively removed from stormwater wetlands, primarily from the forebay. Sediment removal
disturbs stable vegetation cover and disrupts flowpaths through the wetland. The top few inches
of sediment should be stockpiled so that it can be replaced over the surface of the wetland after
the completion of sediment removal to re-establish the vegetative cover using its own seed
bank. Accumulated sediment should be removed from around inlet and outlet structures.

Important maintenance procedures include:

1. Immediately following construction of the stormwater wetland, conduct bi-weekly inspections
and water wetland plants bi-weekly until vegetation becomes established (commonly six
weeks).
2. Before and immediately after plant installation, monitor water level and adjust to ensure that
plants are not completely inundated.
3. No portion of the stormwater wetland will be fertilized after the first initial fertilization that is
required to establish the wetland plants.
4. Maintain stable groundcover in the drainage area to reduce the sediment load to the
wetland.
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5. Inspect the embankment by a dam safety expert at least once annually. Any problems that
are found shall be repaired immediately.
6. After the stormwater wetland is established, inspect it monthly and within 24 hours after
every storm event greater than 1.0 inches (or 1.5 inches if in a Coastal County).
7. Keep a maintenance record in a log in a known set location. Any deficiencies noted in an
inspection will be corrected, repaired or replaced immediately. Deficiencies can affect the
integrity of structures, safety of the public, and the pollutant removal efficiency of the SCM.

Table 6: Sample Operation and Maintenance Agreement for Stormwater Wetlands
SCM element: Potential problems: How to remediate the problem:
Entire SCM Trash/debris is present. Remove the trash/debris.
Perimeter of wetland

Areas of bare soil and/or erosive
gullies have formed.
Regrade the soil if necessary to remove
the gully, and then plant a ground cover
and water until it is established. Provide
lime and a one-time fertilizer application.
Vegetation is too short or too long. Maintain vegetation at an appropriate
height. (6-12” with no scalping)
Inlet device: pipe or
swale

The pipe is clogged (if applicable). Unclog the pipe. Dispose of the sediment
offsite.
The pipe is cracked or otherwise
damaged (if applicable).
Replace the pipe.
Erosion is occurring in the swale (if
applicable).
Regrade the swale if necessary to smooth
it over and provide erosion control devices
such as reinforced turf matting or riprap to
avoid future problems with erosion.
Forebay

Sediment has accumulated in the
forebay to a depth of less than 15” or
that inhibits the forebay from
functioning well.
Search for the source of the sediment and
remedy the problem if possible. Remove
the sediment and dispose of it in a location
where it will not cause impacts to streams
or the BMP.
Erosion has occurred. Provide additional erosion protection such
as reinforced turf matting or riprap if
needed to prevent future erosion problems.
Weeds are present. Remove the weeds, preferably by hand. If
a pesticide is used, wipe it on the plants
rather than spraying.
Deep pool, shallow water
and shallow land areas

Algal growth covers over 30% of the
deep pool and shallow water areas.
Consult a professional to remove and
control the algal growth.
Cattails, phragmites or other
invasive plants cover 30% of the
deep pool and shallow water areas.
Remove invasives by physical removal or
by wiping them with pesticide (do not
spray) – consult a professional.
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The temporary inundation zone
remains flooded more than 5 days
after a storm event.
Unclog the outlet device immediately.
Plants are dead, diseased or dying. Determine the source of the problem:
soils, hydrology, disease, etc. Remedy the
problem and replace plants. Provide a
one-time fertilizer application to establish
the ground cover if necessary.

Sediment has accumulated and
reduced the depth to 75% of the
original design depth of the deep
pools.

Search for the source of the sediment and
remedy the problem if possible. Remove
the sediment and dispose of it in a location
where it will not cause impacts to streams
or the BMP.
Embankment

A tree has started to grow on the
embankment.
If tree is <6” in diameter, remove the tree.
If >6” in diameter, consult a dam safety
specialist to remove the tree.
An annual inspection by appropriate
professional shows that the
embankment needs repair.
Make all needed repairs.
Evidence of muskrat or beaver
activity is present.
Consult a professional to remove muskrats
or beavers and repair any holes or erosion.
Micropool Sediment has accumulated and
reduced the depth to 75% of the
original design depth.
Search for the source of the sediment and
remedy the problem if possible. Remove
the sediment and dispose of it in a location
where it will not cause impacts to streams
or the BMP.
Outlet Structure Clogging has occurred. Clean out the outlet device. Dispose of the
sediment off-site.
The outlet device is damaged Repair or replace the outlet device.
Receiving water Erosion or other signs of damage
have occurred at the outlet.
Repair erosion as necessary.
Add additional energy dissipation such as
fresh rip rap as necessary.
Contact the NC Division of Water
Resources for technical advice.

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Old Versus New Design Standards
Old Versus New Design Standards
The following is a summary of some of the changes in stormwater wetland design standards
between the archived version of the BMP Manual and the current MDC for stormwater wetlands.
It is intended to capture the highlights only; any stormwater wetland MDC that are not captured
in this table are still required per 15A NCAC 02H .1054.
Old manual requirements New MDC
Drawdown time for the
design volume
2-5 days 2-5 days
Sizing Based on the surface area needed to
pond water 12”
Based on the surface area needed to
pond water 15”
SHWT requirements Permanent pool shall be within 6” of
the SHWT (either above or below) or
a liner shall be provided
No requirements regarding SHWT
Required spacing for
herbaceous plants
Required to be 2 foot on center Should be 2 foot on center average, may
distribute throughout the planting zone to
avoid the deepest areas of the wetland.
Required size for plants Specific minimum pot sizes were
specified
The manual suggests containers holding
3.6 to 6.8 cubic inches of media (for
example, and not limited to, 72, 50 and
IP 110) but allows for other container
sizes or bare root stock for some species
and conditions when appropriate.
Plant lists Plant recommendations were limited. A much more extensive list of plants is
provided based on advice from NC
growers and other plant experts in NC.
Minimum length to width ratio 1.5:1 with 3:1 recommended Specific ratio not given; instead, inlet(s)
and outlet shall be located to avoid short
circuiting.
Forebay design Not specified Forebay should be deeper at the
entrance, shallower at the exit.
Trash rack Not required Trash rack or other device to exclude
trash from the outlet structure required.

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References
References for Plant Wildlife Value

American Wildlife and Plants: A Guide To Wildlife Food Habits, Alexander C. Martin,
Herbert S. Zim and Arnold L. Nelson (1989) ISBN 10: 0486207935 / ISBN 13: 9780486207933
Caterpillars of Eastern North America: A Guide to Identification and Natural History,
David L. Wagner, Princeton Field Guides, 2005 ISBN-10: 0691121443
Department of Ecology, State of Washington, “An On-line Version of an Aquatic Plant
Identification Manual for Washington's Freshwater Plants at
http://www.ecy.wa.gov/programs/wq/plants/plantid2/categories.html (Accessed December 12,
2017).
Florida Native Plant Society “Learn About Native Plants” at
http://www.fnps.org/natives/natives (Accessed December 12, 2017).
Forest Plants of the Southeast and their Wildlife Uses, James H. Miller and Karl V. Miller,
University of Georgia Press, 2005. ISBN: 0820327484
Illinois Wildflowers maintained by Dr. John Hilty at http://www.illinoiswildflowers.info/index.htm
(Accessed October 13 and December 12, 2017).
Ladybird Johnson Wildflower Center Plant Database (Accessed October 10 and December
12, 2017) https://www.wildflower.org/plants/result.php?id_plant=chgl2
Landscaping for Wildlife with Native Plants, Chris Moorman, Mark Johns, Liessa Thomas
Bowen, North Carolina State University Cooperative Extension Service, 2002.
https://content.ces.ncsu.edu/landscaping-for-wildlife-with-native-plants
Personal Observations, Shannon Currey, Hoffman Nursery, Rougemont, NC.
Personal Observations, staff of North Carolina Botanical Garden, Chapel Hill, NC. (Mike Kunz,
NCBG)
USDA Natural Resources Conservation Service Plant Fact Sheets
https://www.nrcs.usda.gov/Internet/FSE_PLANTMATERIALS/publications/lapmcfs7566.pdf
Wildflowers and Plant Communities of the Southern Appalachian Mountains and
Piedmont, A Naturalist's Guide to the Carolinas, Virginia, Tennessee, and Georgia, Timothy P.
Spira, 2011. ISBN: 978-0-8078-7172-0

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Photo Gallery
Photo Gallery
Figure 11: View of Wetland with Long Flow Path
(Caldwell Co. Photo by Seth Nagy)

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Figure 12: Stormwater Wetlands, Washington, DC & Raleigh, NC

REFERENCE 8

NCDEQ Riprap Lined Plunge Pool for Cantilever Outlet Design, Last
revised Jan. 23, 1986.
RIPRAP LINED PLUNGE POOL FOR CANTILEVER OUTLET (Version 8.99)
(Reference Design Note No. 6 (Second Edition), Jan. 23, 1986 FORMULAS & COMPUTATIONS
g = acceleration of gravity 32.20
JOB:Cumberland ACP CY SPR 10A Q/(g*d^5)^(1/2) = dimensionless parameter 1.00
DESIGNER:JRH Date:8/29/2018 Zd = water depth above channel invert 0.00
CHECKER:MHK Date:8/29/2018 Vo = conduit discharge velocity 5.09
Vh = horiz. velocity component of jet impingement 5.09
INPUT DATA:Vv = vert. velocity component of jet impingement 6.95
Conduit Diameter D =0.50 ft TAN,a = jet impingement slope 1.36
Conduit Discharge:Q =1.00 cfs Vp = jet velocity at impingement 8.62
Conduit Slope at Outlet:S =0.00 ft/ft Xp = horiz. distance from conduit exit to center of
Conduit Outlet Invert Elevation:El, CO =91.50 ft jet at impingement with tailwater 1.10
Tailwater Elevation:El, TW =91.00 ft Fd = densimetric Froude number 2.37
Outlet Channel Invert Elevation:El, CH =91.00 ft Zp/D 1.00
Zma = maximum pool depth when Zp/D<=1 0.75
Water Density: RHO =1.00 Zmb = maximum pool depth when Zp/D > 1 0.64
Bed/Riprap Particle Density: (Default 2.64)RHOS =2.64 Zm = pool depth to be used 0.75
D, 50 Riprap Size:RS =0.25 ft 1+25*RS/D = parameter used in beaching check 13.50
Riprap Thickness: (2.5*D, 50 recommended)RT =0.63 ft Xm = horiz. distance from conduit exit to center
Bedding Thickness: (6 inch min. rec.) (Enter 0 for geotextile)BT =0.50 ft of plunge pool 1.63
Side Slope Ratio:Zw =2.00 ft/ft Le = min. horiz. distance from center of pool to
Upstream End Slope Ratio:Zlu =3.00 ft/ft water surface contour at upstream or
Downstream End Slope Ratio:Zld =3.00 ft/ft downstream end of pool 1.37
Combined End Slope Ratio:Z1 =3.00 ft/ft We2 = one-half pool width at center at water
surface elevation 1.24
OUTPUT---POOL LOCATION AND DIMENSIONS:Lr2 = one-half pool length at bottom of pool 0.27
Vert. Dist. from Tailwater to Conduit Invert:Zp =0.50 ft Wr2 = one-half pool width at bottom of pool 0.25
Submergence Check: (If Zp < 0 , Use Zp = 0)Use Zp =0.50 ft Lru = adjusted upstream horiz. length from center of
Beaching Check: [Q/(gD^5)^0.5 <= (1.0+25*D,50/D)]O.K.pool to water surface contour at upstream
**Beaching Controlled**end of pool 2.07
Distance from Conduit Exit to C/L Pool:Xm =1.63 ft Lrd = adjusted downstream horiz. length from center
Pool depth at C/L Below Conduit Invert:Zp+0.8Zm =1.10 ft of pool to water surface contour at
Pool Bottom Elev:El,PB =90.40 ft downstream end of pool 2.07
Pool Bottom Length:2Lr2 =0.55 ft Lr = adjusted horiz. length from center of pool
Pool Bottom Width:2Wr2 =0.49 ft to water surface contour at upstream or
Upstream Pool Length at Tailwater Elev.:Lru =2.07 ft downstream end of pool 2.07
Downstream Pool Length at Tailwater Elev.:Lrd =2.07 ft Wr = adjusted horiz. width from center of pool
Pool Width at Tailwater Elev.:2Wr =2.89 ft to water surface contour 1.45
Check Side Slope Ratio: (Wr>=We)O.K.A,2 = horiz. pool area at bottom of pool 0.27
**Side Slope Ratio Zw O.K.**A,1 = horiz. pool area at channel invert elev.11.98
Check Min. End Slope Ratio: (Lru & Lrd >= Le)O.K.V,p = pool volume between bottom and outlet channel
**End Slope Ratios O.K.**invert elevation 0.10
Check Upstream Length: (Lru >= Xm)O.K.A,2r = horiz. pool area at bottom of riprap elev.0.59
**End Slope Ratio Zlu O.K.**A,1r = horiz. pool area at channel invert elevation
Pool Bottom Elev. at Bottom of Riprap:El, BR =89.78 ft contour at bottom surface of riprap 46.04
Pool Bottom Elev. at Bottom of Bedding:El, BB =89.28 ft V,pr = volume of pool measured from bottom surface of
OUTPUT---VOLUMES BELOW WATER SURFACE ELEVATION:riprap 0.78
Volume of Excavation (measured from bottom A,2b = horiz. pool area at bottom of bedding elev.0.94
surface of bedding):V,pbs =2.1 cu yd A,1b = horiz. pool area at channel invert elevation
Volume of Rock Riprap:V,rs =0.7 cu yd contour at bottom surface of bedding 89.20
Volume of Bedding:V,bs =1.3 cu yd V,pb = volume of pool measured from bottom surface of
bedding 2.11
Spreadsheet developed by D. Hurtz, Midwest NTC, 1/90
Spreadsheet modified by M. Dreischmeier, Eau Claire TC, Wis., 3/98 2Lr2e = excavation length at bottom of riprap 0.75
Design Note No. 6 (Second Edition), Jan. 23, 1986 2Wr2e = excavation width at bottom of riprap 0.79
"Riprap Lined Plunge Pool for Cantilever Outlet"Wre = adjusted horiz. width across pool
Natural Resources Conservation Service from bottom of riprap at water surface contour 5.69
Engineering Division Lrue = adjusted upstream horiz. length from center of
pool to bottom of riprap at water surface contour
at upstream end of pool 4.05
Lrde = adjusted downstream horiz. length from center
of pool to bottom of riprap at outlet channel
invert elevation at downstream end of pool 4.05
Lre = adjusted horiz. length from center of pool
to bottom of riprap at water surface contour at
upstream or downstream end of pool 4.05
A,2 = horiz. pool area at bottom of pool 0.27
A,1s = horiz. pool area at water surface elev 11.98
V,ps = pool volume between bottom and water
surface elevation 0.10
A,2r = horiz. pool area at bottom of riprap elev 0.59
A,1rs = horiz. pool area at water surface elevation
contour at bottom surface of riprap 46.04
V,prs = volume of pool measured from bottom surface of
riprap to water surface elevation 0.78
2Lr2b = excavation length at bottom of bedding 0.91
2Wr2b = excavation width at bottom of bedding 1.03
Wrb = adjusted horiz. width from center of pool
to bottom of bedding at water surface contour 7.92
Lrub = adjusted upstream horiz. length from center of
pool to bottom of bedding at water surface contour
at upstream end of pool 5.55
Lrdb = adjusted downstream horiz. length from center
of pool to bottom of bedding at outlet channel
invert elevation at downstream end of pool 5.55
Lrb = adjusted horiz. length from center of pool
to bottom of bedding at water surface contour at
upstream or downstream end of pool 5.55
A,2b = horiz. pool area at bottom of bedding elev 0.94
A,1bs = horiz. pool area at water surface elevation
contour at bottom surface of bedding 87.91
V,pbs = volume of pool measured from bottom surface of
bedding to water surface elevation 2.08
Areas for geotextile:
A,b = bottom 0.59
A,lr = left & right sides 24.22
A,us = u.s. end 12.53
A,ds = d.s. end 12.53
A,p = perimeter 27.57
A,gt = total area 8.61
RIPRAP LINED PLUNGE POOL FOR CANTILEVER OUTLET
Reference Design Note No. 6 (Second Edition), Jan. 23, 1986
Elev. 91.5 C Elev.
91.0
Elev.
1.1 90.4
0.5
1 1
3.0 3.0
0.8
1.6
2.1 4.0
SECTION A-A
5.7
2.9
0.5 1
0.6 2.0
0.8 SECTION B-B
B
A A
ROCK GRADATION
% Passing Size (in)B
100 6 Cumberland ACP CY SPR 10A
60-85 4.5 LANDOWNER
25-50 3
5-20 1.5 DESIGNER:JRH
0-5 0.6 SHEET ___ OF ___
OUTLET PIPE
RIPRAP LINED PLUNGE POOL FOR CANTILEVER OUTLET (Version 8.99)
(Reference Design Note No. 6 (Second Edition), Jan. 23, 1986 FORMULAS & COMPUTATIONS
g = acceleration of gravity 32.20
JOB:Cumberland ACP CY SPR 10A Q/(g*d^5)^(1/2) = dimensionless parameter 1.00
DESIGNER:JRH Date:8/29/2018 Zd = water depth above channel invert 0.00
CHECKER:MHK Date:8/29/2018 Vo = conduit discharge velocity 5.09
Vh = horiz. velocity component of jet impingement 5.09
INPUT DATA:Vv = vert. velocity component of jet impingement 6.95
Conduit Diameter D =0.50 ft TAN,a = jet impingement slope 1.36
Conduit Discharge:Q =1.00 cfs Vp = jet velocity at impingement 8.62
Conduit Slope at Outlet:S =0.00 ft/ft Xp = horiz. distance from conduit exit to center of
Conduit Outlet Invert Elevation:El, CO =91.50 ft jet at impingement with tailwater 1.10
Tailwater Elevation:El, TW =91.00 ft Fd = densimetric Froude number 2.37
Outlet Channel Invert Elevation:El, CH =91.00 ft Zp/D 1.00
Zma = maximum pool depth when Zp/D<=1 0.75
Water Density: RHO =1.00 Zmb = maximum pool depth when Zp/D > 1 0.64
Bed/Riprap Particle Density: (Default 2.64)RHOS =2.64 Zm = pool depth to be used 0.75
D, 50 Riprap Size:RS =0.25 ft 1+25*RS/D = parameter used in beaching check 13.50
Riprap Thickness: (2.5*D, 50 recommended)RT =0.63 ft Xm = horiz. distance from conduit exit to center
Bedding Thickness: (6 inch min. rec.) (Enter 0 for geotextile)BT =0.50 ft of plunge pool 1.63
Side Slope Ratio:Zw =2.00 ft/ft Le = min. horiz. distance from center of pool to
Upstream End Slope Ratio:Zlu =3.00 ft/ft water surface contour at upstream or
Downstream End Slope Ratio:Zld =3.00 ft/ft downstream end of pool 1.37
Combined End Slope Ratio:Z1 =3.00 ft/ft We2 = one-half pool width at center at water
surface elevation 1.24
OUTPUT---POOL LOCATION AND DIMENSIONS:Lr2 = one-half pool length at bottom of pool 0.27
Vert. Dist. from Tailwater to Conduit Invert:Zp =0.50 ft Wr2 = one-half pool width at bottom of pool 0.25
Submergence Check: (If Zp < 0 , Use Zp = 0)Use Zp =0.50 ft Lru = adjusted upstream horiz. length from center of
Beaching Check: [Q/(gD^5)^0.5 <= (1.0+25*D,50/D)]O.K.pool to water surface contour at upstream
**Beaching Controlled**end of pool 2.07
Distance from Conduit Exit to C/L Pool:Xm =1.63 ft Lrd = adjusted downstream horiz. length from center
Pool depth at C/L Below Conduit Invert:Zp+0.8Zm =1.10 ft of pool to water surface contour at
Pool Bottom Elev:El,PB =90.40 ft downstream end of pool 2.07
Pool Bottom Length:2Lr2 =0.55 ft Lr = adjusted horiz. length from center of pool
Pool Bottom Width:2Wr2 =0.49 ft to water surface contour at upstream or
Upstream Pool Length at Tailwater Elev.:Lru =2.07 ft downstream end of pool 2.07
Downstream Pool Length at Tailwater Elev.:Lrd =2.07 ft Wr = adjusted horiz. width from center of pool
Pool Width at Tailwater Elev.:2Wr =2.89 ft to water surface contour 1.45
Check Side Slope Ratio: (Wr>=We)O.K.A,2 = horiz. pool area at bottom of pool 0.27
**Side Slope Ratio Zw O.K.**A,1 = horiz. pool area at channel invert elev.11.98
Check Min. End Slope Ratio: (Lru & Lrd >= Le)O.K.V,p = pool volume between bottom and outlet channel
**End Slope Ratios O.K.**invert elevation 0.10
Check Upstream Length: (Lru >= Xm)O.K.A,2r = horiz. pool area at bottom of riprap elev.0.59
**End Slope Ratio Zlu O.K.**A,1r = horiz. pool area at channel invert elevation
Pool Bottom Elev. at Bottom of Riprap:El, BR =89.78 ft contour at bottom surface of riprap 46.04
Pool Bottom Elev. at Bottom of Bedding:El, BB =89.28 ft V,pr = volume of pool measured from bottom surface of
OUTPUT---VOLUMES BELOW WATER SURFACE ELEVATION:riprap 0.78
Volume of Excavation (measured from bottom A,2b = horiz. pool area at bottom of bedding elev.0.94
surface of bedding):V,pbs =2.1 cu yd A,1b = horiz. pool area at channel invert elevation
Volume of Rock Riprap:V,rs =0.7 cu yd contour at bottom surface of bedding 89.20
Volume of Bedding:V,bs =1.3 cu yd V,pb = volume of pool measured from bottom surface of
bedding 2.11
Spreadsheet developed by D. Hurtz, Midwest NTC, 1/90
Spreadsheet modified by M. Dreischmeier, Eau Claire TC, Wis., 3/98 2Lr2e = excavation length at bottom of riprap 0.75
Design Note No. 6 (Second Edition), Jan. 23, 1986 2Wr2e = excavation width at bottom of riprap 0.79
"Riprap Lined Plunge Pool for Cantilever Outlet"Wre = adjusted horiz. width across pool
Natural Resources Conservation Service from bottom of riprap at water surface contour 5.69
Engineering Division Lrue = adjusted upstream horiz. length from center of
pool to bottom of riprap at water surface contour
at upstream end of pool 4.05
Lrde = adjusted downstream horiz. length from center
of pool to bottom of riprap at outlet channel
invert elevation at downstream end of pool 4.05
Lre = adjusted horiz. length from center of pool
to bottom of riprap at water surface contour at
upstream or downstream end of pool 4.05
A,2 = horiz. pool area at bottom of pool 0.27
A,1s = horiz. pool area at water surface elev 11.98
V,ps = pool volume between bottom and water
surface elevation 0.10
A,2r = horiz. pool area at bottom of riprap elev 0.59
A,1rs = horiz. pool area at water surface elevation
contour at bottom surface of riprap 46.04
V,prs = volume of pool measured from bottom surface of
riprap to water surface elevation 0.78
2Lr2b = excavation length at bottom of bedding 0.91
2Wr2b = excavation width at bottom of bedding 1.03
Wrb = adjusted horiz. width from center of pool
to bottom of bedding at water surface contour 7.92
Lrub = adjusted upstream horiz. length from center of
pool to bottom of bedding at water surface contour
at upstream end of pool 5.55
Lrdb = adjusted downstream horiz. length from center
of pool to bottom of bedding at outlet channel
invert elevation at downstream end of pool 5.55
Lrb = adjusted horiz. length from center of pool
to bottom of bedding at water surface contour at
upstream or downstream end of pool 5.55
A,2b = horiz. pool area at bottom of bedding elev 0.94
A,1bs = horiz. pool area at water surface elevation
contour at bottom surface of bedding 87.91
V,pbs = volume of pool measured from bottom surface of
bedding to water surface elevation 2.08
Areas for geotextile:
A,b = bottom 0.59
A,lr = left & right sides 24.22
A,us = u.s. end 12.53
A,ds = d.s. end 12.53
A,p = perimeter 27.57
A,gt = total area 8.61
RIPRAP LINED PLUNGE POOL FOR CANTILEVER OUTLET
Reference Design Note No. 6 (Second Edition), Jan. 23, 1986
Elev. 91.5 C Elev.
91.0
Elev.
1.1 90.4
0.5
1 1
3.0 3.0
0.8
1.6
2.1 4.0
SECTION A-A
5.7
2.9
0.5 1
0.6 2.0
0.8 SECTION B-B
B
A A
ROCK GRADATION
% Passing Size (in)B
100 6 Cumberland ACP CY SPR 10A
60-85 4.5 LANDOWNER
25-50 3
5-20 1.5 DESIGNER:JRH
0-5 0.6 SHEET ___ OF ___
OUTLET PIPE

ATTACHMENT 9

Drawings

ATLANTIC COAST PIPELINE PROJECT STORMWATER PERMIT APPLICATION
CONTRACTOR YARD - CUMBERLAND COUNTY
(CY 10-A)
FAYETTEVILLE, CUMBERLAND COUNTY, NORTH CAROLINA
ISSUED FOR CONSTRUCTION
VICINITY MAP
NOT TO SCALE
0
DOMINION ENERGY TRANSMISSION, INC.
925 WHITE OAKS BOULEVARD
BRIDGEPORT, WV 26330
804-517-8155
PREPARED BY
9751 SOUTHERN PINE BLVD
CHARLOTTE, NC 28273
[phone]
PREPARED FOR
OWNER:DOMINION ENERGY TRANSMISSION, INC.
ADDRESS:925 WHITE OAKS BOULEVARD
BRIDGEPORT, WV 26330
PHONE NO.:804-517-8155
CONTACT NAME:JUSTIN REED
CONTACT E-MAIL ADDRESS:[e-mail]
PROJECT REPRESENTATIVE:S&ME, INC.
ADDRESS:9751 SOUTHERN PINE BLVD.
CHARLOTTE, NC 28273
PHONE NO.:704-523-4726
CONTACT NAME:CHRISTOPHER J.L. STAHL, P.E.
CONTACT E-MAIL ADDRESS:[e-mail]
SITE LOCATION
1" = 1000'
COUNTY LOCATION
SITE LOCATION
N
N
Sheet List Table
Sheet Number Sheet Title
0 COVER SHEET
1 OVERALL STORMWATER SITE PLAN
2 STORMWATER WETLAND - LANDSCAPE PLAN
3 CROSS SECTIONS
4 STORMWATER MEASURES - DETAILS 1 OF 2
5 STORMWATER MEASURES - DETAILS 2 OF 2
SEPTEMBER 11, 2018
SITE
2000
1834
24
1839
1838
1834
95
1006
24
GAGA
GA
E
E
E
E
E
TS
GP
G 281
G
G
LM
PIEDMONT
LM
PIEDMONT
90410045701
Dow
ni
n
g
LAT:35°02'38.27"
LON:78°49'20.7146"
APPROX.
LOCATION
APPROX.
LOCATION
Roa
d
90
E Q U I P M E N T
TRAI
L
E
R
S
G R
A

V

E

L

R

O

A

D
21'
21'
TBM 1
3/8" REBAR W/ CAP
EL. 92.58'
TBM 2
3/8" REBAR W/ CAP
EL. 92.00'
100' ROW
JOHN S HAIR
PARCEL 0457-40-6622
(52.4 ACRES)
MARY J YOUNG
PARCEL 0457-20-1369
(41.2 ACRES)
HOWARD H R & RICHARD KING
PARCEL 0457-21-1811
(6.7 ACRES)
JEANNE BRYAN DAVIS
PARCEL 0457-20-4762
(0.45 ACRES)
ELLA J CLARK
PARCEL 0456-39-9627
(60.4 ACRES)
MATTIE JACOBS WILLIS
PARCEL 0456-29-8803
(0.18 ACRES)
CHARLENE LEE JACOBS
PARCEL 0456-29-7898
(0.24 ACRES)
CHARLENE LEE JACOBS
PARCEL 0456-29-7985
(0.55 ACRES)
ARCHIE JACOBS
PARCEL 0457-20-7073
(0.26 ACRES)
JAMES L BARTON
PARCEL 0457-20-7160
(0.44 ACRES)
ROSE J MATTHIES
PARCEL 0457-20-7147
(0.18 ACRES)
NC Ro
u
t
e

2
4

(
9
4
'
)

5
5

M
P
H

S
P
E
E
D

L
I
M
I
T
Accord Road(Unpaved Road)NC Ro
u
t
e

2
4

(
9
4
'
)

5
5

M
P
H

S
P
E
E
D

L
I
M
I
T55 MPH40' WIDE DRIVEWAY ENTRANCE
MARTHA L HAIR &
KATHY RADCLIFF
PARCEL 0457-51-1976
(1.7 ACRES)
GATE POSTS
GRAVEL
PARKING LOT
(12.3 ACRES)
GRAVEL
PARKING LOT
(3.2 ACRES)
GRAVEL
PARKING
LOT
(3.2 ACRES)STOR
A
G
E

U
N
I
T
S
FUEL

T
A
N
K
S
92 949494949494949292
92949290929494
96
9
6
94 96949294
9294969494TOP O
F

B
E
R
M

=

9
5
.
1
TOP
O
F
B
E
R
M
=
9
5.
1
TOP OF BERM = 95.1TOP OF BERM = 94.1TOP OF BERM =
9
4
.
1 TOP OF BERM = 94.1TOPSOIL
SEGREGATION
(1.0 ACRES)
TOPSOIL
SEGREGATION
(2.9 ACRES)
46'
94
94
94
94
94
94
94
9492
92
9492949494 92 9294949494
90929492949898969496
98
9492
94
92949494 94DRAWING PATH: q:\7235\17\008 dominion - acp contractor yards\sy10A\PCSW2 recover.DWGDRAWING NUMBER
PROJECT NUMBER BYDESCRIPTIONDATENO.CHKAPV9751 SOUTHERN PINE BLVD
CHARLOTTE, NC 28273
[phone]
ENGINEERING FIRM
LICENSE NUMBER: F-0176
PROPOSED CONTRACTOR YARD (CY 10-A)ATLANTIC COAST PIPELINE PROJECTCUMBERLAND COUNTY, NORTH CAROLINA7235-17-008
1 5OVERALL STORMWATER SITE PLAN0 100 200 300
(IN FEET)GRAPHIC SCALE
VICINITY MAP
1" = 2000"
REF: ESRI USA TOPO
NOTE:
1.BASE DRAWING AND MAIN YARD FEATURES FROM I3 ENGINEERING
AND CONSULTING, LLC (SP10 CY ALT01).
2.ON THE BERM STRUCTURE AND PERIMETER FILL SLOPES,
NON-CLUMPING TURF GRASS SHALL BE PROVIDED, AND TREES AND
WOODY SHRUBS SHALL NOT BE ALLOWED.
3.LATEST E&SC DETAILS PROVIDED BY ERM NC, INC, ISSUED 07/02/2018.
4.SITE IS CURRENTLY ZONED PLANNED INDUSTRIAL DISTRICT M(P)
PROPOSED GRADE CONTOUR
LIMITS OF DISTURBANCE
STREAM
EXISTING GRADE CONTOUR
SCM MAINTENANCE EASEMENT
EXISTING WETLAND
TEMPORARY INUNDATION ZONE
SHALLOW WATER ZONE
GRAVEL AREA
TOPSOIL STOCKPILE
LEGEND
N
JERSEY CONCRETE BARRIERS
TWO 24" DIA. RCP CULVERTS
INVERT EL. 91
OUTLET EL. 90.5
(SEE E&SC PLANS SHEET 3)
EX. 18" CULVERT
DIVERSION SWALE
(REF. E&SC PLANS
SHEET 6, DETAIL 5)
DIVERSION SWALE
(REF. E&SC PLANS
SHEET 6, DETAIL 5)
DIVERSION SWALE
(REF. E&SC PLANS
SHEET 6, DETAIL 5)
PROP. (2) 18" CULVERT & OUTLET PROTECTION
(REF.E&SC PLANS SHEET 8, DETAIL 5)
PROP. (2) 18" CULVERT & OUTLET
PROTECTION
(REF. E&SC PLANS SHEET 8, DETAIL 5)
SCM MAINTENANCE
EASEMENT
SCM MAINTENANCE
EASEMENT
SCM MAINTENANCE
EASEMENT
EXPAND MAINTENANCE
BERM 10' WIDE
EXPAND MAINTENANCE
BERM 10' WIDE
ROCK DAM INSTALLED DURING CONSTRUCTION,
SEE E&SC PLANS SHEET 6, DETAIL 6
ROCK DAM INSTALLED DURING CONSTRUCTION,
SEE E&SC PLANS SHEET 6, DETAIL 6
STORMWATER WETLAND 221
INSET B
INSET A
NO CONTRACTOR ACCESS
ON ACCORD RD
1000 MHKJRHCJSTOP OF DIVERSION
BERM: EL. 94.5
STORMWATER WETLAND 222
ISSUED FOR CONSTRUCTION09/11/20180
90929210'
50'
22'
TOP
O
F
B
E
R
M
=
9
5.
1
TOP OF BERM = 95.1TEMPORARY POOL
ELEVATION 92.5'
FOREBAY
NON-FOREBAY DEEP POOLS
BOTTOM EL. 90.25
TEMPORARY INUNDATION ZONE
4,288 SF
(SEE NOTE 2)
SHALLOW WATER ZONE
4,608 SF
(SEE NOTE 1)
TWO (2) 24" DIA. RCP
CULVERTS 72' LF (EACH)
INLET INV. EL. 91
OUTLET INV. EL. 90.5
2'X3' PRECAST
CONCRETE RISER
0+00
1+00
2+00
3+00
3+120+001+001+08FOREBAY
46'
JERSEY CONCRETE
BARRIER
10'
SCM MAINTENANCE
EASEMENT
TOP OF BERM EL. 92.5
B
3
B'
3A3
A'395
95
94
9493
9395949594939292
9293
94
93
92
949293NON-EROSIVE N.A.G. P300 MATTING
NON-EROSIVE N.A.G. P300 MATTING
90 92
929294
TOP OF BERM = 94.150'
10'
22'
TOP OF BERM
=

9
4
.
1 TOP OF BERM = 94.1NON-FOREBAY DEEP POOLS
BOTTOM EL. 90.25
TEMPORARY INUNDATION ZONE
12,165 SF
(SEE NOTE 2)
SHALLOW WATER ZONE
13,385 SF
(SEE NOTE 1)
8'
FOREBAYS
0+00
1+00
2+00
3+00
3+58
TEMPORARY POOL
ELEVATION 92.25'
TOP OF BERM EL. 92.25
SCM MAINTENANCE EASEMENT
D
3 C3C'393939294
94
92 94929393
9393 2'X3' PRECAST
CONCRETE RISER
D'
3
0+001+002+003+00NON-EROSIVE N.A.G. P300 MATTING
NON-EROSIVE N.A.G. P300 MATTING
DRAWING PATH: q:\7235\17\008 dominion - acp contractor yards\sy10A\PCSW2 recover.DWGDRAWING NUMBER
PROJECT NUMBER BYDESCRIPTIONDATENO.CHKAPV9751 SOUTHERN PINE BLVD
CHARLOTTE, NC 28273
[phone]
ENGINEERING FIRM
LICENSE NUMBER: F-0176
INSET A
STORMWATER WETLAND 222
SCALE 1"=20'
INSET B
STORMWATER WETLAND 221
SCALE 1"=30'
PROPOSED GRADE CONTOUR
SCM MAINTENANCE EASEMENT
LIMITS OF DISTURBANCE
STREAM
EXISTING GRADE CONTOUR
EXISTING WETLAND
TEMPORARY INUNDATION ZONE
SHALLOW WATER ZONE
SLOPE MATTING
LEGEND
1000
NOTES:
1.THE SHALLOW WATER ZONE SHALL BE PLANTED
AT A MINIMUM DENSITY OF 50 HERBACEOUS
PLANTS PER 200 SQUARE FEET (EQUIVALENT TO 2
FOOT ON CENTER SPACING).
2.THE TEMPORARY INUNDATION ZONE SHALL BE
PLANTED ACCORDING TO ONE OF THE
FOLLOWING OPTIONS:
(a)50 HERBACEOUS PLANTS PER 200 SQUARE
FEET (EQUIVALENT TO 2-FOOT ON CENTER
SPACING);
(b)EIGHT SHRUBS PER 200 SQUARE FEET
(EQUIVALENT TO 5 FOOT ON CENTER
SPACING); OR
(c)ONE TREE AND 40 GRASS-LIKE HERBACEOUS
PLANTS PER 100 SQUARE FEET
3.NO WOODY PLANT MATERIALS WILL BE
INSTALLED IN EMBANKMENTS OR MAINTAINED
ACCESS AREAS.
4.NO CATTAILS SHALL BE PLANTED IN THE
WETLAND.
5.PLANTING SHALL BE INSTALLED SEVERAL WEEKS
PRIOR TO THE FIRST FROST.
6.PLANT MATERIAL, SPECIES, SIZE, PLANTING
FORMS, AND LOCATIONS SUBJECT TO CHANGE
BASED ON AVAILABILITY AND FIELD CONDITIONS
AT THE TIME OF PLANTING. PLANT MATERIAL
SPECIES, PLANTING FORMS, QUANTITIES, AND
SIZES ARE SPECIFIED IN TABLE 1 AND 2.
7.IMMEDIATELY FOLLOWING CONSTRUCTION OF
THE STORMWATER WETLAND, BI-WEEKLY
INSPECTIONS WILL BE CONDUCTED AND
WETLAND PLANTS WILL BE WATERED BI-WEEKLY
UNTIL VEGETATION BECOMES ESTABLISHED
(COMMON SIX WEEKS).
8.NO PORTION OF THE STORMWATER WETLAND
WILL BE FERTILIZED AFTER THE FIRST INITIAL
FERTILIZATION THAT IS REQUIRED TO ESTABLISH
THE WETLAND PLANTS.
9.PLANTING AREA SHALL BE INSPECTED IN 12
MONTHS AND SUPPLEMENTARY PLANTS WILL BE
PLANTED TO REPLENISH LOSSES.
TWO PLANTING MATERIAL SOURCES:
MELLOW MARSH FARM, INC.
1312 WOODY STORE ROAD
SILER CITY, NC 27344
PHONE: [phone]
FAX: [phone]
HTTPS://MELLOWMARSHFARM.COM/PROPOSED CONTRACTOR YARD (CY 10-A)ATLANTIC COAST PIPELINE PROJECTCUMBERLAND COUNTY, NORTH CAROLINA7235-17-008
2 5STORMWATER WETLAND - LANDSCAPE PLAN4
5
PLUNGE POOL
2
5
SLOPE
4
5
PLUNGE POOL
3
5
TYPICAL EARTHEN BERM DETAIL
3
5
TYPICAL EARTHEN BERM DETAIL
CAROLINA WETLAND SERVICES
NATIVE PLANT NURSERY
CAROLINA WETLAND SERVICES
550 E WESTINGHOUSE BLVD
CHARLOTTE, NC 28273
TEL: [phone]
FAX: [phone]
HTTP://WWW.CWS-INC.NET/NATIVE-PLANT-NURSERY/
1
4
STORMWATER WETLAND
1
4
STORMWATER WETLAND MHKISSUED FOR CONSTRUCTION09/11/20180JRHCJSMATTING
2
5
SLOPE MATTING
ELEVATION (IN FEET)ELEVATION (IN FEET)80
90
100
80
90
100
0+00 1+00 2+00 3+00 3+58ELEVATION (IN FEET)ELEVATION (IN FEET)80
90
100
80
90
100
0+00 1+00 2+00 3+00 3+12
ELEVATION (IN FEET)ELEVATION (IN FEET)80
90
100
80
90
100
0+00 1+00 2+00 3+00ELEVATION (IN FEET)ELEVATION (IN FEET)80
90
100
80
90
100
0+00 1+001+08
DRAWING PATH: q:\7235\17\008 dominion - acp contractor yards\sy10A\PCSW2 recover.DWGDRAWING NUMBER
PROJECT NUMBER BYDESCRIPTIONDATENO.CHKAPV9751 SOUTHERN PINE BLVD
CHARLOTTE, NC 28273
[phone]
ENGINEERING FIRM
LICENSE NUMBER: F-0176
PROPOSED CONTRACTOR YARD (CY 10-A)ATLANTIC COAST PIPELINE PROJECTCUMBERLAND COUNTY, NORTH CAROLINA7235-17-008
3 5CROSS SECTIONAPPROX. EXISTING
GROUND SURFACE
PROPOSED FINAL GRADE
FOREBAY
NON-FOREBAY DEEP POOL
EARTHEN BERM TOP EL. 92.25
APPROX. EXISTING
GROUND SURFACE
PROPOSED FINAL GRADE
FOREBAY
NON-FOREBAY DEEP POOLS
PERMANENT POOL ELEVATION
TEMPORARY POOL ELEVATION
APPROX. EXISTING
GROUND SURFACE
PROPOSED FINAL GRADE
FOREBAY
NON-FOREBAY DEEP POOL
APPROX. EXISTING
GROUND SURFACE
PROPOSED FINAL GRADE
NON-FOREBAY DEEP POOL
APPROX. EXISTING GROUND SURFACE
PROPOSED FINAL GRADE
PERMANANT POOL ELEVATION
TEMPORARY INUNDATION ZONE LIMIT
LEGEND
SECTION A-A'SECTION B-B'
SECTION C-C'SECTION D-D'
PERMANENT POOL ELEVATION
TEMPORARY POOL ELEVATION
PERMANENT POOL ELEVATION
TEMPORARY POOL ELEVATION
PERMANENT POOL ELEVATION
TEMPORARY POOL ELEVATION
0 10 20 30
(IN FEET)GRAPHIC SCALE
0 50 100 150
(IN FEET)GRAPHIC SCALE
VERTICAL SCALE HORIZONTAL SCALE MHKJRHCJSNOTE:
1.THE SEASONAL HIGH WATER TABLE DEPTH WAS FOUND IN
S&EC SOIL EVALUATION, LOCATED IN ATTACHMENT 7,
DATED MARCH 30, 2018.
WETLAND 222 SHWT: 13" BELOW GROUND SURFACE
WETLAND 221 SHWT: 5" BELOW GROUND SURFACE
WETLAND 221 WETLAND 221
WETLAND 222 WETLAND 222
ISSUED FOR CONSTRUCTION09/11/20180EL 89.75 EL 89.25
EL 89.25
EL 89.75
EL 89.25
EL 89.75
3:
1

S
L
O
P
E
2' X 3' PRECAST
CONCRETE RISER
BERM CREST ELEV.
6" DIA. PVC PIPE
(OR ENGINEER APPROVED EQUAL)
3:1 S
L
O
P
E
PLASTIC TRASH RACK
3 FT.
2 FT. (MIN.)
2 FT. (MIN.)
TOP OF RISER ELEV.
INSTALL ANTI-SEEP COLLAR
ROCK DAM INSTALLED DURING
CONSTRUCTION, SEE E&SC PLANS
NON-FOREBAY DEEP POOLS
FOREBAY
TEMPORARY INUNDATION ZONE
OUTLET INVERT EL.
3" DIA. PVC PIPES AND ELBOW
(OR ENGINEER APPROVED EQUAL)2'
1
2
1
2
PERMANENT POOL ELEV.
TEMPORARY POOL ELEV.
SHALLOW WATER ZONE (AVG. DEPTH OF 6")
36"
WETLAND 221 RISER FRONT VIEW
2' X 3' PRECAST
CONCRETE RISER
6"
6" MIN
3" DIA. ORIFICE INV: 91.75'
18"
36"
WETLAND 222 RISER FRONT VIEW
2' X 3' PRECAST
CONCRETE RISER
6"
6" MIN
3" DIA. ORIFICE INV: 91.75'
18"DRAWING PATH: q:\7235\17\008 dominion - acp contractor yards\sy10A\STORMWATER DETAILS.dwgDRAWING NUMBER
PROJECT NUMBER BYDESCRIPTIONDATENO.CHKAPV9751 SOUTHERN PINE BLVD
CHARLOTTE, NC 28273
[phone]
ENGINEERING FIRM
LICENSE NUMBER: F-0176
PROPOSED CONTRACTOR YARD (CY 10-A)ATLANTIC COAST PIPELINE PROJECTCUMBERLAND CO, NORTH CAROLINA7235-17-008
4 5STORMWATER MEASURES - DETAILS 1 OF 2CONSTRUCTION SPECIFICATIONS
1.CONSIDER CONSTRUCTION SEQUENCING SO THAT VEGETATION CAN BE PLANTED
AND THE WETLAND BROUGHT ONLINE WITHIN 14 DAYS. PLANTS MAY NEED TO BE
WATERED DURING THIS TIME IF THE DEVICE IS NOT BROUGHT ONLINE THE SAME
DAY. STABILIZATION MAY BE IN THE FORM OF FINAL VEGETATION PLANTINGS OR
A TEMPORARY MEANS UNTIL THE VEGETATION BECOMES ESTABLISHED. A GOOD
TEMPORARY MEANS OF STABILIZATION IS A WET HYDROSEED MIX. FOR RAPID
GERMINATION, SCARIFY THE SOIL TO A HALF-INCH PRIOR TO HYDROSEEDING.
2.INLET AND OUTLET CHANNELS SHOULD BE PROTECTED FROM SCOUR THAT MAY
OCCUR DURING PERIODS OF HIGH FLOW. STANDARD EROSION CONTROL
MEASURES SHOULD BE USED. THE LAND QUALITY SECTION OF THE NORTH
CAROLINA DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES AND THE
U.S. DEPARTMENT OF AGRICULTURE NATURAL RESOURCE CONSERVATION
SERVICE (NRCS) CAN PROVIDE INFORMATION ON EROSION AND SEDIMENT
CONTROL TECHNIQUES.
3.THE STORMWATER WETLAND SHOULD BE STAKED AT THE ONSET OF THE
PLANTING SEASON. WATER DEPTHS IN THE WETLAND SHOULD BE MEASURED TO
CONFIRM THE ORIGINAL PLANTING ZONES. AT THIS TIME, IT MAY BE NECESSARY
TO MODIFY THE PLANTING PLAN TO REFLECT ALTERED DEPTHS OR THE
AVAILABILITY OF WETLAND PLANT STOCK. SURVEYED PLANTING ZONES SHOULD
BE MARKED ON AN “AS-BUILT” OR RECORD DESIGN PLAN AND LOCATED IN THE
FIELD USING STAKES OR FLAGS.
4.THE WETLAND DRAIN SHOULD BE FULLY OPENED FOR NO MORE THAN 3 DAYS
PRIOR TO THE PLANTING DATE (WHICH SHOULD COINCIDE WITH THE DELIVERY
DATE FOR THE WETLAND PLANT STOCK) TO PRESERVE SOIL MOISTURE AND
WORKABILITY.
5.THE MOST COMMON AND RELIABLE TECHNIQUE FOR ESTABLISHING AN
EMERGENT WETLAND COMMUNITY IN A STORMWATER WETLAND IS TO
TRANSPLANT NURSERY STOCK OBTAINED FROM LOCAL AQUATIC PLANT
NURSERIES.
6.THE OPTIMAL PERIOD FOR TRANSPLANTING EXTENDS FROM EARLY APRIL TO
MID-JUNE SO THAT THE WETLAND PLANTS WILL HAVE A FULL GROWING SEASON
TO BUILD THE ROOT RESERVES NEEDED TO SURVIVE THE WINTER. HOWEVER,
SOME SPECIES MAY BE PLANTED SUCCESSFULLY IN EARLY FALL. CONTACT
YOUR NURSERY WELL IN ADVANCE OF CONSTRUCTION TO ENSURE THAT THEY
WILL HAVE THE DESIRED SPECIES AVAILABLE.
7.POST-NURSERY CARE OF WETLAND PLANTS IS VERY IMPORTANT IN THE
INTERVAL BETWEEN DELIVERY OF THE PLANTS AND THEIR SUBSEQUENT
INSTALLATION BECAUSE THEY ARE PRONE TO DESICCATION. STOCK SHOULD BE
FREQUENTLY WATERED AND SHADED.
EROSION CONTROL:
CONSTRUCT THE STRUCTURE SO THAT THE DISTURBED AREA IS MINIMIZED. DIVERT
SURFACE WATER AWAY FROM THE BARE AREAS. COMPLETE THE EMBANKMENT
BEFORE ADDITIONAL UPSTREAM AREA IS CLEARED. STABILIZE THE EMERGENCY
SPILLWAY EMBANKMENT AND ALL OTHER DISTURBED AREAS ABOVE THE CREST OF
THE PRINCIPAL SPILLWAY IMMEDIATELY AFTER CONSTRUCTION. REFER TO THE
NCDEQ EROSION AND SEDIMENT CONTROL MANUAL.
MAINTENANCE
1.IMMEDIATELY FOLLOWING CONSTRUCTION OF THE STORMWATER WETLAND,
CONDUCT BI-WEEKLY INSPECTIONS AND WATER WETLAND PLANTS BI-WEEKLY
UNTIL VEGETATION BECOMES ESTABLISHED (COMMONLY SIX WEEKS).
2.BEFORE AND IMMEDIATELY AFTER PLANT INSTALLATION, MONITOR WATER LEVEL
AND ADJUST TO ENSURE THAT PLANTS ARE NOT COMPLETELY INUNDATED.
3.NO PORTION OF THE STORMWATER WETLAND WILL BE FERTILIZED AFTER THE
FIRST INITIAL FERTILIZATION THAT IS REQUIRED TO ESTABLISH THE WETLAND
PLANTS.
4.MAINTAIN STABLE GROUNDCOVER IN THE DRAINAGE AREA TO REDUCE THE
SEDIMENT LOAD TO THE WETLAND.
5.INSPECT THE EMBANKMENT BY A DAM SAFETY EXPERT AT LEAST ONCE
ANNUALLY. ANY PROBLEMS THAT ARE FOUND SHALL BE REPAIRED IMMEDIATELY.
6.AFTER THE STORMWATER WETLAND IS ESTABLISHED, INSPECT IT MONTHLY AND
WITHIN 24 HOURS AFTER EVERY STORM EVENT GREATER THAN 1.0 INCHES (OR
1.5 INCHES IF IN A COASTAL COUNTY).
7.KEEP A MAINTENANCE RECORD IN A LOG IN A KNOWN SET LOCATION. ANY
DEFICIENCIES NOTED IN AN INSPECTION WILL BE CORRECTED, REPAIRED OR
REPLACED IMMEDIATELY. DEFICIENCIES CAN AFFECT THE INTEGRITY OF
STRUCTURES, SAFETY OF THE PUBLIC, AND THE POLLUTANT REMOVAL
EFFICIENCY OF THE SCM.
8.IF SEDIMENT ACCUMULATES IN THE FOREBAY IN A MANNER THAT REDUCES ITS
DEPTH TO 15 INCHES THEN THE FOREBAY SHALL BE CLEANED OUT AND
RETURNED TO ITS DESIGN STATE.
(REFER TO THE NCDEQ STORMWATER DESIGN MANUAL REGARDING STORMWATER
WETLANDS FOR ANY DESIGN CONCERNS)
WETLAND SPECIFICATIONS
WETLAND FEATURE WETLAND 221 WETLAND 222
BERM CREST ELEVATION 94.1'95.1'
OUTLET PIPE INLET INVERT 91.50'91.50'
OUTLET PIPE DIAMETER 6"6"
OUTLET PIPE LENGTH 30'35'
OUTLET PIPE OUTLET INVERT 91.25'91.25'
TOP OF RISER ELEVATION 94.50'94.50'
PERMANENT POOL ELEVATION 91.75'91.75'
TEMPORARY POOL ELEVATION 92.25'92.50'
TEMPORARY INUNDATION ZONE
DEPTH 6"9"
MIN. NON-FOREBAY DEEP POOL DEPTH 18"18"
FOREBAY DEPTH 24"24"
TYP.STORMWATER WETLAND1
4 NOT TO SCALE
CONSTRUCTION SEQUENCE
1.REMOVE EROSION AND SEDIMENT CONTROL DEVICES (SKIMMER, BAFFLES, ETC.).
2.EXCAVATE TOP OF THE BASIN TO EL. 91.75 TO REMOVE ANY UNWANTED CONTAMINATES
THAT MAY HINDER THE WETLAND THRIVING ABILITY.
3.INSTALL STORMWATER DEVICES (RISER, OUTLET PIPE, PLUNGE POOL, ETC.)
4.EXPAND BERM WIDTH TO 10'. MAINTAIN 3:1 SLOPES AND APPLY MATTING PER DETAIL 2,
SHEET 5.
5.CONSTRUCT EARTHEN BERM NEAR ROCK CHECK DAM ACCORDING TO DETAIL 3, SHEET 5.
6.GRADING WETLAND AREA ACCORDING TO STORMWATER WETLAND LANDSCAPING PLAN,
SHEET 2.
7.PLANT WETLAND VEGETATION.
4
5
PLUNGE POOL
EARTHEN BERM
5
3
MHKJRHCJSISSUED FOR CONSTRUCTION09/11/20180
EXTEND BLANKET A MINIMUM OF 3'-0"
OVER CREST OF SLOPE.
TRENCHING NEEDED IF A MINIMUM
OF 3'-0" IS NOT AVAILABLE AT THE
CREST OF SLOPE
FOR END ROLL
OVERLAP, 4-INCHES
OVERLAP SIDE SEAM 4-INCHES
FOR SIDE SEAM ABUTMENT
BLANKET TO EXTEND A
MINIMUM OF 3 FOOT
BEYOND TOE OF SLOPE.
FOR BOTTOM OF SLOPE
TERMINATION
TEMPORARY MATTING (SLOPES) NOTES:
1.TEMPORARY MATTING INSTALLED ON SLOPES IN UPLAND AREAS SHALL BE
NAG BIONET S75BN OR ENGINEER APPROVED EQUIVALENT.
2.PREPARE SOIL BEFORE INSTALLING TEMPORARY MATTING, INCLUDING ANY
NECESSARY APPLICATION OF LIME, FERTILIZER, AND SEED.
3.BEGIN AT THE TOP OF THE SLOPE BY ANCHORING THE TEMPORARY
MATTING IN A 6-INCH DEEP X 6-INCH WIDE TRENCH WITH APPROXIMATELY
12-INCH OF TEMPORARY MATTING EXTENDED BEYOND THE UP-SLOPE
PORTION OF THE TRENCH. ANCHOR THE TEMPORARY MATTING WITH A
ROW OF STAPLES/STAKES AS PER THE MANUFACTURERS SPECIFICATIONS.
BACKFILL THE TRENCH AFTER STAPLING. APPLY SEED TO SURFACE AND
FOLD REMAINING 12-INCH PORTION OF TEMPORARY MATTING BACK OVER
SEED AND COMPACTED SOIL. SECURE TEMPORARY MATTING OVER
COMPACTED SOIL WITH A ROW OF STAPLES/STAKES SPACED PER THE
MANUFACTURERS SPECIFICATIONS..
4.ROLL THE TEMPORARY MATTING DOWN OR HORIZONTALLY ACROSS THE
SLOPE. TEMPORARY MATTING WILL UNROLL WITH APPROPRIATE SIDE
AGAINST THE SOIL SURFACE. ALL TEMPORARY MATTING MUST BE
SECURELY FASTENED TO SOIL SURFACE BY PLACING STAPLES/STAKES IN
APPROPRIATE LOCATIONS AS PER THE MANUFACTURERS SPECIFICATIONS.
5.THE EDGES OF PARALLEL TEMPORARY MATTING MUST BE STAPLED WITH A
MINIMUM 4-INCH OVERLAP.
6.CONSECUTIVE TEMPORARY MATTING SPLICED DOWN THE SLOPE MUST BE
PLACED END OVER END (SHINGLE STYLE) WITH A MINIMUM 4-INCH
OVERLAP. STAPLE THROUGH OVERLAPPED AREA PER THE MANUFACTURERS
SPECIFICATIONS.
7.IN LOOSE SOIL CONDITIONS, THE USE OF STAPLE OR STAKE LENGTHS
GREATER THAN 6-INCH MAY BE NECESSARY TO PROPERLY SECURE THE
TEMPORARY MATTING.
*TEMPORARY MATTING (SLOPES) MAINTENANCE NOTES:
1.INSPECT TEMPORARY MATTING AT LEAST WEEKLY AND AFTER EACH
RAINFALL EVENT THAT EXCEEDS 0.5 INCHES WITHIN A 24 HOUR PERIOD.
2.GOOD CONTACT WITH THE GROUND MUST BE MAINTAINED, AND EROSION
MUST NOT OCCUR BENEATH THE TEMPORARY MATTING.
3.ANY AREAS OF THE TEMPORARY MATTING THAT ARE DAMAGED OR NOT IN
CLOSE CONTACT WITH THE GROUND SHALL BE REPAIRED AND STAPLED.
4.IF EROSION OCCURS DUE TO POORLY CONTROLLED DRAINAGE, THE
PROBLEM SHALL BE FIXED AND THE ERODED AREA PROTECTED.
5.MONITOR AND REPAIR THE TEMPORARY MATTING AS NECESSARY UNTIL
GROUND COVER IS ESTABLISHED.
*REF:NCDENR EROSION AND SEDIMENT CONTROL PLANNING AND DESIGN
MANUAL, CHAPTERS 6 AND 8 REVISED, MAY 2013
TYPICAL MATTING (SLOPES) DETAIL2
5 NOT TO SCALE
TOP OF SLOPE
EARTHEN BERM WITH ROCK DAM
INSTALLATION:
ONCE THE EARTHEN BERM IS CONSTRUCTED USING SITE FILL MATERIAL OR ACCEPTABLE OFFSITE FILL MATERIAL, THE EARTHEN BERM SHOULD BE LINED WITH
NAG P300 MATTING TO PREVENT EROSION.
INSPECTION AND MAINTENANCE:
INSPECT THE EARTHEN BERM EVERY SEVEN (7) CALENDAR DAYS AND WITHIN 24-HOURS AFTER EACH RAINFALL EVENT THAT PRODUCES ½-INCHES OR MORE
OF PRECIPITATION. INSPECT FOR SEDIMENT AND DEBRIS ACCUMULATION. INSPECT AND REPAIR PROMPTLY AS REQUIRED.
SEDIMENT SHOULD BE REMOVED WHEN IT REACHES 1/2 THE ORIGINAL BERM HEIGHT.
TYPICAL EARTHEN BERM AND ROCK DAM SECTION
TYPICAL EARTHEN BERM AND ROCK DAM PLAN VIEW
NOTE:
SEE EROSION AND SEDIMENT CONTROL
PLANS, SHEET 6 FOR ROCK DAM DETAIL
EARTHEN BERM WITH NAG P300 MATTING
(OR ENGINEER APPROVED EQUIVALENT)
FLOW FROM WETLAND
3
5
TYPICAL EARTHEN BERM DETAIL
NOT TO SCALE
FLOW FROM WETLAND
EARTHEN BERM WITH NAG P300 MATTING
(OR ENGINEER APPROVED EQUIVALENT)
BASIN BERM
ROCK DAM (SEE E&SC Plan SHEET 6, DETAIL 6)
HEIGHT VARIES
EARTHEN BERM DIMENSIONS:
WETLAND:HEIGHT:
221S 6"
222S 9"
TIE-IN ELEVATION:
WETLAND:ELEVATION:
221S 92.25'
222S 92.50'
EL. 91.75'
2 121
2'
ROCK DAM (SEE E&SC PLAN SHEET 6, DETAIL 6)
PLAN
A
A
C
D B
A
SECTION A-A
F
E
3" DIA. GRAVEL, 9" THICKNESS ON FILTER FABRIC
MAINTENANCE
INSPECT PLUNGE POOL AREAS AT LEAST WEEKLY AND AFTER EACH RAINFALL OCCURRENCE
THAT EXCEEDS ONE-HALF (0.5) INCH WITHIN A 24-HOUR PERIOD. REMOVE SEDIMENT AND
RESTORE TO ORIGINAL DIMENSIONS WHEN SEDIMENT ACCUMULATES TO ONE-HALF THE
HEIGHT OF THE POOL. CHECK EMBANKMENT, LINING, AND OUTLET AREA FOR ANY DAMAGE
AND REPAIR AS NECESSARY, AS SOON AS PRACTICAL.DRAWING PATH: q:\7235\17\008 dominion - acp contractor yards\sy10A\STORMWATER DETAILS.dwgDRAWING NUMBER
PROJECT NUMBER BYDESCRIPTIONDATENO.CHKAPV9751 SOUTHERN PINE BLVD
CHARLOTTE, NC 28273
[phone]
ENGINEERING FIRM
LICENSE NUMBER: F-0176
PROPOSED CONTRACTOR YARD (CY 10-A)ATLANTIC COAST PIPELINE PROJECTCUMBERLAND CO, NORTH CAROLINA7235-17-008
5 5STORMWATER MEASURES - DETAILS 2 OF 24
5
PLUNGE POOL
NOT TO SCALE
NOTE: REFER TO CALCULATION PACKAGE FOR FURTHER DETAILS AND SIZING.MHKJRHCJSISSUED FOR CONSTRUCTION09/11/20180