20071579 Ver 1_Stormwater Info_20080422 (24)

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STORMWATER NARRATIVE AND
SUPPORTING CALCULATIONS
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NORTH CAROLINA CENTER FOR AUTOMOTIVE RESEARCH
North Carolina Center for Automotive Research
Garysburg, Northampton County, North Carolina
April 2008
Prepared for:
NCCAR, Inc.
Prepared By:
LTG ANDS ?N S"+t F th'r
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1730 Varsity Drive
Raleigh, North Carolina 27606
Phone: [phone]
Fax: [phone]
M&C Project No. 04921-0003
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PROJECT DESCRIPITON
' The purpose of the North Carolina Center for Automotive Research (NCCAR) is to construct a
non-profit facility to meet the ever-evolving product research, testing and development
demands of the automotive industry. NCCAR is designed to provide real-world vehicle testing
capability that will enable its clients to apply research to improve vehicular performance,
efficiency and safety.
' These goals will be achieved through the development of several main components. The site
will feature a 4.2 mile Ride and Handling course, two vehicle dynamics areas, multiple test
laboratories, client garages, a refueling station and operations and administrations buildings.
Collaboratively, these elements will provide a world-class center that will allow engineers to
' evaluate and develop new vehicles and prove out new systems in the controlled environment
of a test facility.
' SITE DESCRIPTION
The existing site is a 619 acre tract located in Northampton County, northwest of Garysburg,
1 North Carolina. A site delineation of 404 wetlands was performed by Land Management Group,
Inc. and was approved in the field by the U.S. Army Corps of Engineers. As approved, the site
contains approximately 140 acres of freshwater wetlands, most of which are headwaters of the
' Roanoke River. These unnamed tributaries of Arthur's Creek form nearly the entire perimeter of
the site. These tributaries converge in the southern portion of the site and flow into Arthur's
Creek (Stream Classification C) and eventually into the Roanoke River. The North Carolina
Division of Water Quality implements no watershed development or discharge restrictions for
Class C water bodies.
The tract has elevations ranging from 150' to 105', generally sloping from north to south. Slopes
' on the site average 1-2% in most directions, but intensify near the edges of the wetlands.
SOILS
1 According to the Northampton County Generalized Soil Survey, the majority of uplands within
the site are classified as Bonneau sandy loam and Caroline fine sandy loam. Interspersed are
' small pockets of Craven fine sandy loam, Goldsboro sandy loam and Norfolk sandy loam. Soils
along major stream channels consist of Wehadkee loam. Bethera silt loam and Roanoke silt
loam are located in wetland areas further upstream.
' A subsurface exploration report has been performed by S&ME, Inc. Through soil test borings
ranging from 10 to 60 feet, the following was found in the existing soils:
A. Topsoil depths range from 4 to 18 inches deep.
B. Highly plastic clayey silts and silty clays extend below the topsoil in depths ranging
from 5 to 15 feet.
C. Low plasticity silty and sandy clays were found beneath highly plastic soils.
' D. Groundwater levels were recorded at approximate depths of 3.5 to 19 feet below
existing ground elevations.
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S&ME, Inc. concludes that, based on drought conditions in North Carolina at the time of drilling,
measured groundwater levels are likely to rise as more normal rainfall patterns return. The soils
' report also concludes that generally, field measured soils patterns generally align with those
found the Northampton County Generalized Soil Survey Map.
A second S&ME, Inc. report has also been performed to determine the seasonally high water
table depths in the areas of proposed stormwater BMPs. As found at most locations, the SHWT is
found within 6" of the existing ground surface.
STORMWATER IMPROVEMENTS
This project will provide stormwater management based on the guidelines set forth in the North
' Carolina Divions of Water Quality's Stormwater Best Management Practices Manual.
As the site spans approximately 619 acres, a large portion of the site will remain undisturbed.
' Based solely on impervious areas in relation to the site acreage, the site can be classified as low
density according to the "BMP Manual" in that the total impervious area for the site is less than
24%. (See attached table for impervious area breakdown)
4,705,966sf
*100%=17.5%
26,963,640sf
' Also, a drainage area breakdown as required by SWU-101 shows that several individual drainage
areas will be classified as high density based upon the amount of impervious surfaces within
' those watersheds. Further analysis of drainage areas shows that, due to the large amount of
wetlands on the site, some areas in low density drainage areas will require discrete stormwater
management devices. Likewise, not all watersheds in high density drainage areas will require
' discrete stormwater management devices.
To simplify, each drainage area is broken down individually respective of possible wetland
impacts and to justify our conclusions for each watershed.
1 Drainage Area # 1
As shown on the attached table, the proposed impervious area in drainage area #I equates to
only approximately 8.70% over the drainage area. Therefore, this meets the low density
impervious percentage requirement. Also, due to the nature of the construction, stormwater
' runoff will be directed into the wetland areas by means of non-erosive flow which would not be
detrimental to the existing wetlands.
Drainage Area #2
As shown on the attached table, the proposed impervious area is approximately 8.55% of the
total drainage area. For overall project aesthetics, an amenity pond will be located on the
' north side of the Security Kiosk. During rain events, stormwater runoff from the north side main
road will be directed into the pond to recharge water levels. To keep the pond hydrated during
dry periods, the pond bottom will be cut into existing grade where the seasonally high water
table is located less than 6" below existing ground surface, as located by S&ME, Inc. This pond
will be an amenity only and is not to serve as or to be permitted as a stormwater quality device
as defined by DWQ. During large storm events, an overflow device is designed to safely pass
runoff without negatively impacting downstream wetlands. A fountain will be provided and the

' pump designed according to the guidelines in section 10.3.10 of the BMP manual to ensure the
health of pond in drought periods. This pond will be maintained in accordance with the
attached Operations and Maintenance Agreement.
Drainage Area #3
As shown on the attached table, drainage area #3 will contain 4.87% impervious area. This
drainage area meets the impervious area requirements set forth by DWQ to qualify as low
density. All stormwater runoff will be directed into wetland areas by means of sheet flow and will
pass through a 30' vegetated filter.
Drainage Area #3 will not require a discrete stormwater management device.
Drainage Area #4
As shown on the attached table, drainage area #4 will only contain approximately 8.86%
impervious area. Based solely on impervious area, this drainage area qualifies as a low density
area. However, a quick glance might suggest that the amount of wetlands in this area far
outnumbers upland areas. Upon further analysis, the amount of wetlands does create a couple
' of distinctive watersheds. On the far west of the site and west of the largest wetlands area is
where the Emissions and Fuel Cell Labs are located. The total impervious surface in this "pocket"
is 4.60 acres, compared to 36.07 acres of non-impervious area. Thus, only 12.7% impervious
1 surface area and no need for a BMP. Similarly, in the northern part of this drainage area, an
uplands "pocket" sites the proposed engine combustion lab. The total area of the uplands
pocket is 13.22 acres whereas the impervious area is 2.18 acres. This equates to 16.5%
impervious and no need for a BMP.
The conclusion is that the drainage area #4 will not require a discrete stormwater management
device.
Drainage Area #5
1 As shown on the attached table, drainage area #5 will contain no impervious area. The only
development within this watershed will be as a result of grading from construction of either the
Fuel Cell or Emissions Labs. No impervious surface is planned for drainage area #5. Therefore, a
discrete stormwater management device will not be required.
Drainage Area #6
' As shown on the attached table, drainage area #6 will contain approximately 3.80% impervious
area. The impervious area will be from the north part of the Large VDA. As the roadway loops,
most of the area will remain as pervious surfaces, thus eliminating the need for a BMP.
Drainage Area #7
' As shown on the attached table, drainage area #7 will contain approximately 2.03% impervious
area. Much like Drainage Area #6, the impervious area in Drainage Area #7 will be from the
northern loop of the Large VDA. All of the runoff from the main portions of the Large VDA will be
directed into Drainage Areas #8 and #9 and treated as needed in these areas. Therefore,
Drainage Area #7 will not require a BMP.
Drainage Area #8

As shown on the attached table, drainage area #8 will contain approximately 40.951%
impervious area. Based on regulations, drainage area #8 will require a BMP. Based on
proposed grades in relation to natural drainage patterns, at least one BMP will be designed per
Phase II guidelines as set forth in the BMP Manual.
' Drainage Area #9
As shown on the attached table, drainage area #9 will contain approximately 27.87%
impervious area. Based on regulations, drainage area #9 will require a BMP. Due to the amount
of wetlands throughout the watershed, several separated areas of uplands exist. The proposed
Large VDA will contribute approximately 25.22 acres of impervious area into the drainage area.
' As proposed grades in relation with existing drainage patterns dictate, 2 BMPs will provide
stormwater management.
As the Client Garage A is situated within a pocket of wetlands, a BMP will be required to protect
the wetlands from adverse affects from concentrated runoff.
The proposed ride & handling course in this drainage area contributes approximately 3.26 acres
of impervious area. Compared to the total drainage area from the area (36.69 acres), the
impervious area is only 10% of the entire area. As required, all stormwater runoff from this area
will be directed into wetland areas by sheet flow and through a minimum 30' vegetated buffer.
Drainage Area # 10
As shown on the attached table, drainage area # 10 will contain approximately 21.77%
impervious area. Though overall impervious surface area requirements are met, a BMP will be
designed to provide stormwater management for a large portion of the area. Some of the Ride
& Handling course portions are to be designed as low density areas, and as required, all
stormwater runoff will be directed into wetlands areas by sheet flow and through a minimum 30'
vegetated buffer. Most of the impervious areas will drain into one of two designed wet
detention ponds that will provide water quality treatment as well as quantity control for the 1-yr,
24-hr storm as required.
Runoff from the proposed operations, engineering & client garages (phase 1) building will
provide an insignificant amount of runoff into the wetlands based on the adjacent drainage
area, thus no BMP will be provided. A similar situation exists for Drainage Area #11 (see below).
Much of Drainage Area # 10 naturally drained to an isolated wetland pocket. As required by the
project, and if approved, this area will be filled and most of the area will drain as an addition to
Drainage Area # 10.
Drainaae Area #I 1
As shown on the attached table, drainage area # 1 1 will contain approximately 2.13%
impervious area. Therefore, no BMP will be provided in this area. All impervious areas resulting
from the construction of the Administration and Operations Building and associated parking
areas will be directed into wetland areas by sheet flow.

' MAINTENANCE CONSIDERATIONS
The property owner, NCCAR, Inc. shall be responsible for periodic inspection and maintenance
of all permanent indicated stormwater devices. Any measure that fails to function as intended
shall be repaired immediately.

CALCULATIONS
Calculations are included in this package.

1

Impervious Area Description Impervious Area (sq. ff.)
Security Kiosk 485
Operations, Engineering & Client Garages (Phase 1) 15,435
Operations, Engineering & Client Garages
Parking/Driveway Phase 1 52,835
Ride and Handling Course 1,079,411
Covered Parking Lots 28,050
Covered Parking Lots Drive Area 108,442
Event Parking 65,280
Fueling Station 9,350
Fueling Station Parking 12,856
Maintenance & Dry Storage Building 3,150
Maintenance & Dry Storage Building Parking 13,144
Operations, Engineering & Client Garages (Phase 2) 33,609
Operations, Engineering & Client Garages Parking/
Driveway Phase 2 150,842
CD lab 9,800
CD Lab Parking 6,150
Small Vehicle Dynamics Area 401,805
Large Vehicle Dynamics Area 1,842,704
Large VDA Labs 18,700
Large VDA Labs Parking 19,166
Emissions Lab 45,024
Emissions Lab Parking 42,864
Fuel Cell Lab 39,744
Fuel Cell Lab Parking 42,733
Engine Combustion Lab 45,024
Engine Combustion Lab Parking 34,545
Client Garage A 31,414
Client Garage A Parking 57,777

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Client Garage B 31,414
Client Garage B Parking 57,458
Roadway 407,135
Total 4,715,316

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'Boundaries are approximate and are
not meant to be absolute.
SCALE 1" = 1 Mile
Map Source: North Carolina Atlas & Gazetteer. Pg 22-23.2003
NCCAR Project Land Management Group, Inc.
Environmental Consultants FI ure 1. Vicinit Ma
Northampton County, NC Wilmington, N.C. 9 y p
September 2007

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SCALE 1" = 1200'
NCCAR Project
Northampton County, NC
Land Management Group, Inc.
Environmental Consultants
Wilmington, N.C.
September 2007
Figure 2. USGS Topo
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Land Management Group, Inc.
NCCAR Project Environmental Consultants Figure 3. NRCS Soils Map
Northampton County, NC Wilmington, N.C.
September 2007
Land Management Group, Inc.
NCCAR Project Environmental Consultants
Northampton County, NC Wilmington, N.C.
September 2007
Figure 4. 1998 NAPP
Aerial Photograph

' BMP #1 Type// 24-hr Rainfall=2.81 "
Prepared by McKim & Creed, PA
HydroCADO 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/18/2008
' Subcatchment 1S: BMP #1 - Pre-Development
Runoff = 24.04 cfs @ 13.35 hrs, Volume= 6.264 af, Depth> 0.76"
' Runoff by SCS TR-20 method, UH=SCS, Time Span= 1.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr Rainfall=2.81"
' Area (ac) CN Description
99.110 74 Pasture/grassland/range, Good, HSG C
99.110 Pervious Area
Tc Length Slope Velocity Capacity Description
' (min) (feet) (ft/ft) (ft/sec) (cfs)
38.0 250 0.0100 0.11 Sheet Flow,
Grass: Dense n= 0.240 P2= 3.40"
68.3 2,868 0.0100 0.70 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
106.3 3,118 Total

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BMP #1 Type// 24-hr Rainfall=2.81 "
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/18/2008
Subcatchment 2S: BMP #1 - Post - Development
Runoff = 43.05 cfs @ 13.33 hrs, Volume= 10.351 af, Depth> 1.25"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 1.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr Rainfall=2.81"
Area (ac) CN Description
35.910 98 Paved parking & roofs
63.200 74 >75% Grass cover, Good, HSG C
99.110 83 Weighted Average
63.200 Pervious Area
35.910 Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.5 100 0.2000 0.30 Sheet Flow,
Grass: Dense n= 0.240 P2= 3.40"
102.9 5,070 0.0030 0.82 Shallow Concentrated Flow,
Grassed Waterwav Kv= 15.0 fDs
108.4 5,170 Total
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BMP #1 Type// 24-hr Rainfall=2.81"
Prepared by McKim & Creed, PA
HydroCADB 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/18/2008
Pond 3P: BMP #1 - Pond Design
1 Inflow Area = 99.110 ac, Inflow Depth > 1.25"
Inflow 43.05 cfs @ 13.33 hrs, Volume= 10.351 of
Outflow = 23.78 cfs @ 14.29 hrs, Volume= 6.459 af, Atten= 45%, Lag= 57.6 min
Primary = 23.78 cfs @ 14.29 hrs, Volume= 6.459 of
Secondary = 0.00 cfs @ 1.00 hrs, Volume= 0.000 of
Routing by Stor-Ind method, Time Span= 1.00-24.00 hrs, dt= 0.05 hrs
Peak Elev= 109.52'@ 14.29 hrs Surf.Area= 1.687 ac Storage= 4.597 of
Plug-Flow detention time= 202.9 min calculated for 6.445 of (62% of inflow)
Center-of-Mass det. time= 99.0 min ( 1,011.2 - 912.1 )
' Volume Invert Avail.Stora a Stora -ge Description
#1 106.50' 7.272 of Custom Stage Data (Irregular) Listed below (Recalc)
Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area
(feet) (acres) (feet) (acre-feet) (acre-feet) (acres)
106.50 1.316 1,106.0 0.000 0.000 1.316
107.00 1.444 1,137.0 0.690 0.690 1.444
108.00 1.523 1,156.0 1.483 2.173 1.528
109.00 1.604 1,175.0 1.563 3.736 1.613
110.00 1.765 1,772.0 1.684 5.420 4.827
111.00 1.940 2,379.0 1.852 7.272 9.430
' Device Routing Invert Outlet Devices
#1 Primary 105.00' 30.0" x 70.0' long Culvert X 2.00
RCP, square edge headwall, Ke= 0.500
Outlet Invert= 104.50' S= 0.0071 '/' Cc= 0.900 n= 0.013
#2 Device 1 106.50' 6.5" Vert. Orifice/Grate C= 0.600
#3 Device 1 108.65' 60.0 deg x 1.0' long x 0.45' rise Sharp-Crested Vee/Trap Weir
' C= 2.53
#4 Device 1 109.10' 4.00' x 7.00' Horiz. Orifice/Grate Limited to weir flow C=0.600
#5 Secondary 109.60' 35.0' long x 10.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=23.76 cfs @ 14.29 hrs HW=109.52' (Free Discharge)
L1=Culvert (Passes 23.76 cfs of 85.39 cfs potential flow)
2=Orifice/Grate (Orifice Controls 1.84 cfs @ 7.99 fps)
3=Sharp-Crested Vee/Trap Weir (Orifice Controls 2.13 cfs @ 3.75 fps)
=Orifice/Grate (Weir Controls 19.79 cfs @ 2.13 fps)
Secondary OutFlow Max=0.00 cfs @ 1.00 hrs HW=106.50' (Free Discharge)
L5=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
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BMP #1 Type 1124-hr Rainfall=1.00"
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/18/2008
Pond 3P: BMP #1 - Pond Design
Inflow Area = 99.110 ac, Inflow Depth = 0.13"
Inflow _ 2.97 cfs @ 13.59 hrs, Volume= 1.091 of
Outflow 0.51 cfs @ 21.63 hrs, Volume= 0.925 af, Atten= 83%, Lag= 482.7 min
Primary = 0.51 cfs @ 21.63 hrs, Volume= 0.925 of
Secondary = 0.00 cfs @ 1.00 hrs, Volume= 0.000 of
Routing by Stor-Ind method, Time Span= 1.00-60.00 hrs, dt= 0.05 hrs
Peak Elev= 106.98'@ 21.63 hrs Surf.Area= 1.439 ac Storage= 0.663 of
Plug-Flow detention time= 782.3 min calculated for 0.925 of (85% of inflow)
Center-of-Mass det. time= 711.7 min ( 1,723.6 - 1,011.9 )
' Volume Invert Avail.Storage Storage Description
#1 106.50' 7.272 of Custom Stage Data (Irregular) Listed below (Recalc)
Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area
(feet) (acres) (feet) (acre-feet) (acre-feet) (acres)
106.50 1.316 1,106.0 0.000 0.000 1.316
107.00 1.444 1,137.0 0.690 0.690 1.444
108.00 1.523 1,156.0 1.483 2.173 1.528
109.00 1.604 1,175.0 1.563 3.736 1.613
110.00 1.765 1,772.0 1.684 5.420 4.827
111.00 1.940 2,379.0 1.852 7.272 9.430
Device Routing Invert Outlet Devices
#1 Primary 105.00' 30.0" x 70.0' long Culvert X 2.00
RCP, square edge headwall, Ke= 0.500
Outlet Invert= 104.50' S= 0.0071 '/' Cc= 0.900 n= 0.013
#2 Device 1 106.50' 6.5" Vert. Orifice/Grate C= 0.600
#3 Device 1 108.65' 60.0 deg x 1.0' long x 0.45' rise Sharp-Crested Vee/Trap Weir
C= 2.53
#4 Device 1 109.10' 4.00' x 7.00' Horiz. Orifice/Grate Limited to weir flow C=0.600
#5 Secondary 109.60' 35.0' long x 10.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=0.51 cfs @ 21.63 hrs HW=106.98' (Free Discharge)
t--1 =Culvert (Passes 0.51 cfs of 33.87 cfs potential flow)
' 2=Orifice/Grate (Orifice Controls 0.51 cfs @ 2.36 fps)
3=Sharp-Crested Vee/Trap Weir ( Controls 0.00 cfs)
=Orifice/Grate ( Controls 0.00 cfs)
Secondary OutFlow Max=0.00 cfs @ 1.00 hrs HW=106.50' (Free Discharge)
L5=Broad-Crested Rectangular Weir (Controls 0.00 cfs)
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WATER QUALITY POND CALCULATIONS
Project Name
NCCAR BMP #1
Project Number
04921-0003
Date
April 17, 2008
3rd revision
2nd revision
1st revision

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Water Quality Pond Drainage Area Data
Project
Project No.
Date
Total site area
NCCAR BMP #1
04921-0003
April 17, 2008
4,317,035 square feet =
Dra inage area to pond Other Drai nage Area

Impervious areas Existing
[sf] Proposed
s Change
s Existing
sf] Proposed
[sf]
On-site buildings 0 28,050 28,050 0 0
On-site streets 0 0 0 0 0
On-site parkin 0 108,442 108,442 0 0
On-site sidewalks 0 0 0 0 0
Other on-site 0 1,427,821 1,427,821 0 0
Total off-site impervious 0 0 0 0 0
Total Impervious 0 1,564,313 1,564,313 0 0
Dra inage area to pond Other Drai nage Area

Non-impervious areas Existing
s Proposed
s Change
s Existing
[sf] Proposed
[s
On-site grass/landscape 0 0 0 0 0
On-site woods 0 0 0 0 0
Other undeveloped 0 0 0 0 0
Total off-site non-impervious 0 0 0 0 0
Total non-impervious 0 0 0 0 0
Total Drainage Area 4,317,035 4,317,035 0 3,167,850 3,167,850
Percent Impervious 0.0 36.2 36.2 0.0 0.0
Notes:
BMP #1.xls
Site Drainage Area Data
Page 1 of 1
99.11 acres
Printed 4/18/2008 11:11 AM

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Water Quality Pond Surface Area Calculations
Project
Project No
Date
NCCAR BMP #1
04921-0003
April 17, 2008
Total on-site drainage area to pond 4,317,035 square feet
Total impervious area in drainage area 1,564,313 square feet
Average water depth of basin at normal pool 4.0 feet
Location of site Northampton County
Site region Piedmont
% Impervious cover 36.2 percent
If the site is in a coastal area, will a vegetative filter be used? n/a
Surface Area/Drainage Area Ratios:
For a site in the Piedmont 1.3 percent
For a site in a Coastal County w/ Vegetative Filter 2.3 percent
For a site in a Coastal County w/out Vegetative Filter 3.2 percent
Required surface area of pond:
For a site in the Piedmont 56,050.0 square feet
For a site in a Coastal County w/ Vegetative Filter 100,870.0 square feet
For a site in a Coastal County w/out Vegetative Filter 138,100.0 square feet
Notes:
BMP #1.xls
Pond Surface Area Calcs
Page 1 of 1
Printed 4/18/2008 11:11 AM
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Water Quality Pond Stormwater Runoff Volume Calculations
Project
Project No.
Date
Drainage area
Impervious area
Rainfall depth
NCCAR BMP #1
04921-0003
April 17, 2008
4,317,035 square feet
1,564,313 square feet
1.00 inches
Percent Impervious 36.2
R(v)=0.05+0.009*(Percent impervious)
Runoff coefficient - R(v) 0.38
percent
in/in
Runoff volume=(Design rainfall)*(R(v))*(Drainage area)
Runoff volume 135,311.1 cubic feet
Notes:
BMP #1.xls
Runoff Volume Calcs
Page 1 of 1
Printed 4/18/2008 11:11 AM

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1
Water Quality Pond Volume Calculations
Stage-Storage Data for Pond - Temporary Pool
Project NCCAR BMP #1
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
[s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
106.5 0 57,304.0 1.316 57,304.0 1.3 0.0 0.0 0.0 0.0
107 0.5 62,912.0 1.444 5,608.0 0.1 30,054.0 0.7 30,054.0 0.7
108 1.5 66,353.0 1.523 3,441.0 0.1 64,632.5 1.5 94,686.5 2.2
108.65
109
110
111 2.15
2.5
3.5
4.5 68,620.0
69,850.0
76,894.0
84,512.0 1.575
1.604
1.765
1.940 2,267.0
1,230.0
7,044.0
7,618.0 0.1
0.0
0.2
0.2 43,866.2
24,232.2
73,372.0
80,703.0 1.0
0.6
1.7
1.9 138,552.7
162,785.0
236,157.0
316,860.0 2.5
1.6
2.2
3.5

BMP #1.xls
Stage Storage (Temp Pool)
Page 1 of 1
Printed 4/1812008 11:11 AM

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Water Quality Pond Volume Calculations
Stage-Storage Data for Pond - Permanent Pool
Project NCCAR BMP #1
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
[s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
100 0 17,889.0 0.411 17,889.0 0.4 0.0 0.0 0.0 0.0
101 1 20,894.0 0.480 3,005.0 0.1 19,391.5 0.4 19,391.5 0.4
102 2 31,297.0 0.718 10,403.0 0.2 26,095.5 0.6 45,487.0 1.0
103 3 35,515.0 0.815 4,218.0 0.1 33,406.0 0.8 78,893.0 1.4
104 4 39,847.0 0.915 4,332.0 0.1 37,681.0 0.9 116,574.0 1.6
105 5 44,291.0 1.017 4,444.0 0.1 42,069.0 1.0 158,643.0 1.8
106 6 48,849.0 1.121 4,558.0 0.1 46,570.0 1.1 205,213.0 2.0
106.5 6.5 57,304.0 1.316 8,455.0 0.2 26,538.3 0.6 231,751.3 1.7

BMP #1.xls
Stage Storage (Perm Pool)
Page 1 of 1
Printed 4/18/2008 11:11 AM

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Water Quality Pond Volume Calculations
Stage-Storage Data for Pond -Forebays
Project NCCAR BMP #1
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
s . ft.
Area
acres Incremental
Area
[s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
102 0 7,334.0 0.168 7,334.0 0.2 0.0 0.0 0.0 0.0
103 1 8,435.0 0.194 1,101.0 0.0 7,884.5 0.2 7,884.5 0.2
104 2 9,593.0 0.220 1,158.0 0.0 9,014.0 0.2 16, 898.5 0.4
105 3 10,807.0 0.248 1,214.0 0.0 10,200.0 0.2 27,098.5 0.4
106 4 12,078.0 0.277 1,271.0 0.0 11,442.5 0.3 38,541.0 0.5
106.5 4.5 14,510.0 0.333 2,432.0 0.1 6,647.0 0.2 45,188.0 0.4

BMP #1.xls
Stage Storage (Forebays)
Page 1 of 1
Printed 4/18/2008 11:11 AM
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Water Quality Basin Dewatering Time Calculations
Project NCCAR BMP #1
Project No. 04921-0003
Date April 17, 2008
Maximum surface area of basin 68,620 square feet
Maximum head of water above dewatering hole 2.15 feet
Orifice coefficient 0.60
Diameter of each hole 6.5 inches
Number of holes 1
Cross sectional area of each hole =
Cross sectional area of each hole =
Cross sectional area of dewatering hole(s) _
Cross sectional area of dewatering hole(s) _
Dewatering time for basin =
Dewatering time for basin =
Notes:
0.230 square feet
33.2 square inches

0.230 square feet
33.2 square inches

50.4 hours
2.10 days
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Water Quality Pond Summary Information
Project NCCAR BMP #1
Project No. 04921-0003
Date April 17, 2008
Drainage area to pond 4,317,035 square feet = 99.11 acres
Impervious area in drainage area 1,564,313 square feet = 35.91 acres
Bottom of pond elevation 101.00 feet
Normal pool elevation 106.50 feet
Pond volume at normal pool 231,751 cubic feet
Required volume for design rainfall 135,311 cubic feet
Required surface area for pond 56,050 square feet
Volume provided for storage of design rainfall = 138,553 cubic feet at elevation 108.65
Surface area provided at normal pool 57,304 square feet
BMP #1.xls
Summary Data
Page 1 of 1
Printed 4/18/2008 11:12 AM

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4/21/08

RELIM
PROJECT NAME PROJECT NO CONSTR
NCCAR 4921-0003 REVISION
LOCATION BY RECORD
Garysburg, NC GCA OTHER
BMP #1 CHECKED BY (SPECIFY)
GML
Storm Outlet Structure
Structure= BMP #1
Size= 30 in
Q10 = 39.62 cfs
Qfull = 34.50 cfs
Vfull = 7.02 fps
From Fig. 8.06.b.1:
From Fig. 8.06.b.2:
Q10/Qfull = 1.15
V/Vfull = 1.15
V = 8.1 fps
Zone = 2
D5o = 8 in
DMAx = 12 in
Riprap Class = B
Apron Thickness = 12 in
Apron Length = 15.0 ft
Apron Width = 3xDia = 7.5 ft

1 BMP #2 Type// 24-hr Rainfall=2.81 "
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008
' Subcatchment 1S: BMP #2 - Pre-Development
' Runoff = 9.60 cfs @ 12.45 hrs, Volume= 1.311 af, Depth> 0.78"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr Rainfall=2.81"
Area (ac) CN Description
20.230 74 Pasture/grassland/range, Good, HSG C
' 20.230 Pervious Area
Tc Length Slope Velocity Capacity Description
' (min) (feet) (ft/ft) (ft/sec) (cfs)
33.2 250 0.0140 0.13 Sheet Flow,
Grass: Dense n= 0.240 P2= 3.40"
9.7 980 0.0110 1.69 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
42.9 1,230 Total

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1 Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008

' Subcatchment 2S: BMP #2 - Post-Development
Runoff = 30.02 cfs @ 12.04 hrs, Volume= 1.767 af, Depth> 1.05"
Runoff by SCS T R-20 method, UH=SCS, Time Span= 5.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr Rainfall=2.81"
'
Area (ac) CN Description
4.370 98 Paved parking & roofs
15.860 74 >75% Grass cover, Good, HSG C
20.230 79 Weighted Average
15.860 Pervious Area
4.370 Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.2 100 0.0200 1.42 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
10.6 1,083 0.0130 1.71 Shallow Concentrated Flow,
Grassed Waterway Kv= 15.0 fps
11.8 1,183 Total

?J
BMP #2 Type// 24-hr Rainfall=2.81"
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/17/2008
r Pond 3P: BMP #2 - Pond Design
Inflow Area 20.230 ac, Inflow Depth > 1.05"
Inflow 30.02 cfs @ 12.04 hrs, Volume= 1.767 of
Outflow = 8.04 cfs @ 12.29 hrs, Volume= 1.337 af, Atten= 73%, Lag= 14.8 min
Primary = 8.04 cfs @ 12.29 hrs, Volume= 1.337 of
Secondary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 of
Routing by Stor-Ind method, Time Span= 5.00-24.00 hrs, dt= 0.05 hrs
Peak Elev= 116.41'@ 12.29 hrs Surf.Area= 0.373 ac Storage= 0.642 of
Plug-Flow detention time= 152.1 min calculated for 1.337 of (76% of inflow)
' Center-of-Mass det. time= 55.3 min ( 908.5 - 853.2 )
Volume Invert Avail.Storage Storage Description
#1 114.50' 1.759 of Custom Stage Data (Irregular) Listed below (Recalc)
Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area
(feet) (acres) (feet) (acre-feet) (acre-feet) (acres)
114.50 0.273 442.0 0.000 0.000 0.273
115.00 0.326 474.0 0.150 0.150 0.327
116.00 0.359 493.0 0.342 0.492 0.362
117.00 0.394 512.0 0.376 0.868 0.399
118.00 0.430 530.0 0.412 1.280 0.435
119.00 0.530 958.0 0.479 1.759 1.599
' Device Routing Invert Outlet Devices
#1 Primary 113.50' 15.0" x 68.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 113.10' S= 0.0059 '/' Cc= 0.900 n=0.013
#2 Device 1 114.50' 2.5" Vert. Orifice/Grate C= 0.600
#3 Device 1 115.80' 4.00'x 4.00' Horiz. Orifice/Grate Limited to weir flow C= 0.600
#4 Secondary 117.50' 35.0' long x 10.0' breadth Broad-Crested Rectangular Weir
1 Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=8.04 cfs @ 12.29 hrs HW=116.41' (Free Discharge)
L1 =Culvert (Barrel Controls 8.04 cfs @ 6.55 fps)
1:3=Orifice/G 2=Orifice/G rate (Passes < 0.22 cfs potential flow)
rate (Passes < 24.77 cfs potential flow)
Secondary OutFlow Max=0.00 cfs @ 5.00 hrs HW=114.50' (Free Discharge)
L4=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)

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Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 @ 2006 HydroCAD Software Solutions LLC 4/17/2008
Pond 3P: BMP #2 - Pond Design
Inflow Area 20.230 ac, Inflow Depth = 0.07"
Inflow 0.70 cfs @ 12.11 hrs, Volume= 0.118 of
Outflow = 0.06 cfs @ 24.04 hrs, Volume= 0.106 af, Atten= 91%, Lag= 715.7 min
Primary = 0.06 cfs @ 24.04 hrs, Volume= 0.106 of
' Secondary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 of
Routing by Stor-Ind method, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs
' Peak Elev= 114.74'@ 24.04 hrs Surf.Area= 0.298 ac Storage= 0.069 of
Plug-Flow detention time= 703.8 min calculated for 0.106 of (90% of inflow)
' Center-of-Mass det. time= 657.2 min ( 1,628.3 - 971.1 )
Volume Invert Avail.Storage Storage Description
#1 114.50' 1.759 of Custom Stage Data (Irregular) Listed below (Recalc)
Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area
(feet) (acres) (feet) (acre-feet) (acre-feet) (acres)
' 114.50 0.273 442.0 0.000 0.000 0.273
115.00 0.326 474.0 0.150 0.150 0.327
116.00 0.359 493.0 0.342 0.492 0.362
117.00 0.394 512.0 0.376 0.868 0.399
118.00 0.430 530.0 0.412 1.280 0.435
119.00 0.530 958.0 0.479 1.759 1.599
Device Routing Invert Outlet Devices
#1 Primary 113.50' 15.0" x 68.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 113.10' S=0.0059'/' Cc= 0.900 n=0.013
#2 Device 1 114.50' 2.5" Vert. Orifice/Grate C= 0.600
#3 Device 1 115.80' 4.00'x 4.00' Horiz. Orifice/Grate Limited to weir flow C= 0.600
#4 Secondary 117.50' 35.0' long x 10.0' breadth Broad-Crested Rectangular Weir
' Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=0.06 cfs @ 24.04 hrs HW=114.74' (Free Discharge)
t1=Culvert (Passes 0.06 cfs of 4.01 cfs potential flow)
1:3=Orifice/G 2=Orifice/G rate (Orifice Controls 0.06 cfs @ 1.78 fps)
rate ( Controls 0.00 cfs)
' Secondary OutFlow Max=0.00 cfs @ 5.00 hrs HW=114.50' (Free Discharge)
t-4=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)

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WATER QUALITY POND CALCULATIONS
Project Name
NCCAR BMP #2
Project Number
04921-0003
Date
April 17, 2008
3rd revision
2nd revision
1 st revision

17

Water Quality Pond Drainage Area Data
Project
Project No.
Date
Total site area
Dra inage area to pond Other Drai nage Area

Impervious areas Existing
sf] Proposed
Isf] Change
[s Existing
Isf] Proposed
Isf]
On-site buildings 0 46,109 46,109 0 0
On-site streets 0 0 0 0 0
On-site parkin 0 144,115 144,115 0 0
On-site sidewalks 0 0 0 0 0
Other on-site 0 0 0 0 0
Total off-site impervious 0 0 0 0 0
Total Impervious 0 190,224 190,224 0 0
Dra inage area to pond Other Dra inage Area

Non-impervious areas Existing
[sf] Proposed
[sf] Change
[s Existing
Isf] Proposed
sf]
On-site grass/landscape 0 137,267 137,267 0 0
On-site woods 0 0 0 0 0
Other undeveloped 0 0 0 0 0
Total off-site non-impervious 0 0 0 0 0
Total non-impervious 0 137,267 137,267 0 0
Total Drainage Area 881,416 881,416 0 3,167,850 3,167,850
Percent Impervious 0.0 21.6 21.6 0.0 0.0
NCCAR BMP #2
04921-0003
April 17, 2008
881,416 square feet = 20.23 acres
Notes:
BMP #2.xls
Site Drainage Area Data
Page 1 of 1
Printed 4/16/2008 3:18 PM
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Water Quality Pond Surface Area Calculations
Project
Project No
Date
NCCAR BMP #2
04921-0003
April 17, 2008
Total on-site drainage area to pond 881,416 square feet
Total impervious area in drainage area 190,224 square feet
Average water depth of basin at normal pool 3.0 feet
Location of site Northampton County
Site region Piedmont
% Impervious cover 21.6 percent
If the site is in a coastal area, will a vegetative filter be used? n/a
Surface Area/Drainage Area Ratios:
For a site in the Piedmont 1.0 percent
For a site in a Coastal County w/ Vegetative Filter 1.8 percent
For a site in a Coastal County w/out Vegetative Filter 2.6 percent
Required surface area of pond:
For a site in the Piedmont 9,070.0 square feet
For a site in a Coastal County w/ Vegetative Filter 16,100.0 square feet
For a site in a Coastal County w/out Vegetative Filter 22,690.0 square feet
Notes:
BMP #2.xls
Pond Surface Area Calcs
Page 1 of 1
Printed 4/16/2008 3:18 PM
Water Quality Pond Stormwater Runoff Volume Calculations
Project
Project No.
Date
Drainage area
Impervious area
Rainfall depth
NCCAR BMP #2
04921-0003
April 17, 2008
881,416 square feet
190,224 square feet
1.00 inches
Percent Impervious 21.6
R(v)=0.05+0.009*(Percent impervious)
Runoff coefficient - R(v) 0.24
percent
in/in
Runoff volume=(Design rainfall)*(R(v))*(Drainage area)
Runoff volume 17,939.4 cubic feet
Notes:
BMP #2.xls
Runoff Volume Calcs Page 1 of 1 Printed 4/16/2008 3:18 PM

1

1

Water Quality Pond Volume Calculations
Stage-Storage Data for Pond - Temporary Pool
Project NCCAR BMP #2
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
(s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
114.5 0 11,905.0 0.273 11,905.0 0.3 0.0 0.0 0.0 0.0
115 0.5 14,196.0 0.326 2,291.0 0.1 6,525.3 0.1 6,525.3 0.1
115.8 1.3 15,351.0 0.352 1,155.0 0.0 11,818.8 0.3 18,344.1 0.4
116 1.5 15,646.0 0.359 295.0 0.0 3,099.7 0.1 21,443.8 0.3
117 2.5 17,152.0 0.394 1,506.0 0.0 16,399.0 0.4 37,842.8 0.4
118 3.5 18,715.0 0.430 1,563.0 0.0 17,933.5 0.4 55,776.3 0.8
119 4.5 23,080.0 0.530 4,365.0 0.1 20,897.5 0.5 76,673.8 0.9

BMP #2.xls
' Stage Storage (Temp Pool) Page 1 of 1 Printed 4/16/2008 3:18 PM

fl

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Water Quality Pond Volume Calculations
Stage-Storage Data for Pond - Permanent Pool
Project NCCAR BMP #2
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
[s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
107 0 816.0 0.019 816.0 0.0 0.0 0.0 0.0 0.0
108 1 1,450.0 0.033 634.0 0.0 1,133.0 0.0 1,133.0 0.0
109 2 2,268.0 0.052 818.0 0.0 1,859.0 0.0 2,992.0 0.1
110 3 3,115.0 0.072 847.0 0.0 2,691.5 0.1 5,683.5 0.1
111 4 4,932.0 0.113 1,817.0 0.0 4,023.5 0.1 9,707.0 0.2
112 5 6,265.0 0.144 1,333.0 0.0 5,598.5 0.1 15,305.5 0.2
113 6 7,712.0 0.177 1,447.0 0.0 6,988.5 0.2 22,294.0 0.3
114 7 9,361.0 0.215 1,649.0 0.0 8,536.5 0.2 30,830.5 0.4
114.5 7.5 11,905.0 0.273 2,544.0 0.1 5,316.5 0.1 36,147.0 0.3

BMP #2.xls
Stage Storage (Perm Pool) Page 1 of 1 Printed 4/16/2008 3:18 PM
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Water Quality Pond Volume Calculations
Stage-Storage Data for Pond - Forebay
Project NCCAR BMP #2
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
[s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
110 0 592.0 0.014 592.0 0.0 0.0 0.0 0.0 0.0
111 1 911.0 0.021 319.0 0.0 751.5 0.0 751.5 0.0
112 2 1,283.0 0.029 372.0 0.0 1,097.0 0.0 1,848.5 0.0
113 3 1,712.0 0.039 429.0 0.0 1,497.5 0.0 3,346.0 0.1
114 4 2,197.0 0.050 485.0 0.0 1,954.5 0.0 5,300.5 0.1
114.5 4.5 3,072.0 0.071 875.0 0.0 1,317.3 0.0 6,617.8 0.1

BMP #2.xls
Stage Storage (Forebay) Page 1 of 1 Printed 4/16/2008 3:18 PM
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Water Quality Basin Dewatering Time Calculations
Project NCCAR BMP #2
Project No. 04921-0003
Date April 17, 2008
Maximum surface area of basin 15,351.0 square feet
Maximum head of water above dewatering hole 1.5 feet
Orifice coefficient 0.60
Diameter of each hole 2.5 inches
Number of holes 1
Cross sectional area of each hole =
Cross sectional area of each hole =
Cross sectional area of dewatering hole(s) _
Cross sectional area of dewatering hole(s) _
Dewatering time for basin =
Dewatering time for basin =
Notes:
0.034 square feet
4.9 square inches
0.034 square feet
4.9 square inches
62.6 hours
2.6 days
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Water Quality Pond Summary Information
Project NCCAR BMP #2
Project No. 04921-0003
Date April 17, 2008
Drainage area to pond 881,416 square feet = 20.23 acres
Impervious area in drainage area 190,224 square feet = 4.37 acres
Bottom of pond elevation 107.00 feet
Normal pool elevation 114.50 feet
Pond volume at normal pool 36,080 cubic feet
Required volume for design rainfall 17,939 cubic feet
Required surface area for pond 9,070 square feet

Volume provided for storage of design rainfall = 18,344 cubic feet at elevation 115.8
Surface area provided at normal pool 11,905 square feet
BMP #2.xls
Summary Data
Page 1 of 1
Printed 4/16/2008 3:18 PM
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:.i•.>.:.04/21/08 PRELIM
PROJECT NAME PROJECT NO CONSTR
NCCAR 4921-0003 REVISION
LOCATION BY RECORD
Garysburg, NC GCA OTHER
BMP #2 CHECKED BY (SPECIFY)
GML
Storm Outlet Structure
Structure= BMP #2 Quo/Qfull = 2.24
Size= 15 in VNfull = 2.24
Qio = 11.10 cfs V = 9.0 fps
Qfull = 4.95 cfs
Vfull = 4.04 fps
From Fig. 8.06.b.1: Zone = 2
From Fig. 8.06.b.2: D50 = 8 in
DMAx = 12 in
Riprap Class = B
L Apron Thickness = 12 in
Full 3 Apron Length = 7.5 ft
Apron Width = 3xDia = 3.75 ft
Length

BMP #4 Type 1124-hr Rainfall=2.81"
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008
' Subcatchment 1 S: BMP #4 - Pre-Development
Runoff = 4.48 cfs @ 12.03 hrs, Volume= 0.258 af, Depth> 0.79"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr Rainfall=2.81"
1 Area (sf) CN Description
171,001 74 Pasture/grassland/range, Good, HSG C
' 171,001 Pervious Area
Tc Length Slope Velocity Capacity Description
' (min) (feet) (ft/ft) (ft/sec) (cfs)
10.0 Direct Entry,

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BMP #4 Type // 24-hr Rainfall=2.81"
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008
' Subcatchment 2S: BMP #4 - Post-Development
[46] Hint: Tc=O (Instant runoff peak depends on dt)
Runoff = 12.51 cfs @ 11.89 hrs, Volume= 0.515 af, Depth> 1.57"
1 Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr Rainfall=2.81"
Area (sf) CN Description
89,064 98 Paved parking & roofs
81,937 74 >75% Grass cover, Good, HSG C
171,001 87 Weighted Average
'
81,937 Pervious Area
89,064 Impervious Area

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BMP #4
Type// 24-hr Rainfall=2.81 "
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008
Pond 3P: BMP #4 - Wetland Routing
Inflow Area = 3.926 ac, Inflow Depth > 1.57"
Inflow = 12.51 cfs @ 11.89 hrs, Volume= 0.515 of
Outflow = 4.26 cfs @ 12.00 hrs, Volume= 0.326 af, Atten= 66%, Lag= 6.3 min
Primary = 0.12 cfs @ 12.00 hrs, Volume= 0.112 of
Secondary = 4.14 cfs @ 12.00 hrs, Volume= 0.213 of
Routing by Stor-Ind method, Time Span= 5.00-24.00 hrs, dt= 0.05 hrs
Peak Elev= 126.29'@ 12.00 hrs Surf.Area= 9,815 sf Storage= 10,066 cf
Plug-Flow detention time= 189.3 min calculated for 0.325 of (63% of inflow)
Center-of-Mass det. time= 81.0 min ( 896.8 - 815.8 )
Volume Invert Avail.Storage Storage Description
#1 125.00' 17,763 cf Custom Stage Data (Irregular) Listed below (Recalc)
Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area
(feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft)
125.00 5,770 529.0 0 0 5,770
126.00 9,016 419.0 7,333 7,333 14,082
127.00 11,912 440.0 10,430 17,763 15,580
Device Routing Invert Outlet Devices
#1 Primary 125.00' 2.0" Vert. Orifice/Grate C= 0.600
#2 Secondary 126.10' 20.0' long x 10.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=0.12 cfs @ 12.00 hrs HW=126.29' (Free Discharge)
t1=Orifice/Grate (Orifice Controls 0.12 cfs @ 5.29 fps)
Secondary OutFlow Max=4.08 cfs @ 12.00 hrs HW=126.29' (Free Discharge)
L2=Broad-Crested Rectangular Weir (Weir Controls 4.08 cfs @ 1.08 fps)

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BMP #4 Type 11 24-hr Rainfall=1.00"
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008
Pond 3P: BMP #4 - Wetland Routing
Inflow Area
Inflow 3.926 ac,
1.74 cfs @ Inflow Depth = 0.22"
11.90 hrs, Volume=
0.073 of
Outflow = 0.05 cfs @ 15.84 hrs, Volume= 0.070 af, Atten= 97%, Lag= 236.3 min
Primary = 0.05 cfs @ 15.84 hrs, Volume= 0.070 of
Secondary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 of
Routing by Stor-Ind method, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs
1 Peak Elev= 125.27'@ 15.84 hrs Surf.Area= 6,587 sf Storage= 1,689 cf
Plug-Flow detention time= 555.4 min calculated for 0.070 of (95% of inflow)
Center-of-Mass det. time= 531.1 min ( 1,407.2 - 876.1 )
Volume Invert Avail.Storage Storage Description
#1 125.00' 17,763 cf Custom Stage Data (irregular) Listed below (Recalc)
Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area
(feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft)
1 125.00 5,770 529.0 0 0 5,770
126.00 9,016 419.0 7,333 7,333 14,082
127.00 11,912 440.0 10,430 17,763 15,580
Device Routing Invert Outlet Devices
#1 Primary 125.00' 2.0" Vert. Orifice/Grate C= 0.600
#2 Secondary 126.10' 20.0' long x 10.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=0.05 cfs @ 15.84 hrs HW=125.27' (Free Discharge)
t-1=Orifice/Grate (Orifice Controls 0.05 cfs @ 2.10 fps)
Secondary OutFlow Max=0.00 cfs @ 5.00 hrs HW=125.00' (Free Discharge)
t--2=Broad -Crested Rectangular Weir ( Controls 0.00 cfs)

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STORMWATER WETLAND WATER QUALITY CALCULATIONS
Project Name
NCCAR BMP #4
Project Number
04921-0003
Date
April 17, 2008
3rd revision
2nd revision
1 st revision
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Stormwater Wetland Drainage Area Data
Project NCCAR BMP #4
Project No.
Date
Total site area
04921-0003
April 17, 2008
171,001 square feet =
acres
Dra inage area to pond Other Drai nage Area

Impervious areas Existing
[sf] Proposed
[sf] Change
[sf] Existing
[sf] Proposed
[sf]
On-site buildings 0 31,414 31,414 0 0
On-site streets 0 0 0 0 0
On-site parkin 0 57,650 57,650 0 0
On-site sidewalks 0 0 0 0 0
Other on-site 0 0 0 0 0
Total off-site impervious 0 0 0 0 0
Total Impervious 0 89,064 89,064 0 0
Drainage area to pond Other Drai nage Area

Non-impervious areas Existing
[sf] Proposed
[sf] Change
[sf] Existing
[sf] Proposed
[sf]
On-site grass/landscape 0 0 0 0
On-site woods 0 0 0 0 0
Other undeveloped 0 0 0 0 0
Total off-site non-impervious 0 0 0 0 0
Total non-impervious 0 0 0 0 0
Total Drainage Area 171,001 171,001 0 3,167,850 3,167,850
Percent Impervious 0.0 52.1 52.1 0.0 0.0
Notes:
BMP #4.xls
Site Drainage Area Data
Page 1 of 1
3.93
Printed 4/16/2008 3:23 PM

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Stormwater Wetland Stormwater Runoff Volume Calculations
Project
Project No.
Date
Drainage area
Impervious area
Rainfall depth
Percent Impervious
NCCAR BMP #4
04921-0003
April 17, 2008
171,001 square feet
89,064 square feet
1.00 inches
52.1
percent
R(v)=0.05+0.009*(Percent impervious)
Runoff coefficient - R(v) 0.52 in/in
Runoff volume=(Design rainfall)*(R(v))*(Drainage area)
Runoff volume 7,392.3 cubic feet
Notes:
BMP #4.xls
Runoff Volume Calcs
Page 1 of 1
Printed 4/16/2008 3:23 PM
i

1

Stormwater Wetland Volume Calculations
Stage-Storage Data for Wetland - Temporary Pool
Project NCCAR BMP #4
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
[s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
124 0 5,770.0 0.132 5,770.0 0.1 0.0 0.0 0.0 0.0
125 1 9,016.0 0.207 3,246.0 0.1 7,393.0 0.2 7,393.0 0.2
126 2 10,434.0 0.240 1,418.0 0.0 9,725.0 0.2 17,118.0 0.4
127 3 11,912.0 0.273 1,478.0 0.0 11,173.0 0.3 28,291.0 0.5

BMP #4.xls
' Stage Storage (Temp Pool) Page 1 of 1 Printed 4/16/2008 3:23 PM
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Stormwater Wetland Dewatering Time Calculations
Project NCCAR BMP #4
Project No. 04921-0003
Date April 17, 2008
Maximum surface area of basin 9,016 square feet
Maximum head of water above dewatering hole 1.0 feet
Orifice coefficient 0.60
Diameter of each hole 2.00 inches
Number of holes 1
Cross sectional area of each hole =
Cross sectional area of each hole =
Cross sectional area of dewatering hole(s) _
Cross sectional area of dewatering hole(s) _
Dewatering time for basin =
Dewatering time for basin =
Notes:
0.022 square feet
3.1 square inches
0.022 square feet
3.1 square inches
47.7 hours
2.0 days
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Stormwater Wetland Summary Information
Date April 17, 2008
Project NCCAR BMP #4
Project No. 04921-0003
Drainage area to pond 171,001 square feet =
Impervious area in drainage area 89,064 square feet =
Bottom of pond elevation 120.50 feet
Normal pool elevation 124.00 feet
3.93 acres
2.04 acres
Required volume for design rainfall 7,392 cubic feet
Volume provided for storage of design rainfall = 7,393 cubic feet at elevation 125
BMP #4.xls
Summary Data
Page 1 of 1
Printed 4/16/2008 3:23 PM
J
' BMP #5 Type /I 24-hr Rainfall=2.81"
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008
' Subcatchment 11 S: BMP #5 Pre-Development
' Runoff = 4.43 cfs @ 12.50 hrs, Volume= 0.640 af, Depth> 0.78"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 1.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr Rainfall=2.81"
Area (ac) CN Description
9.880 74 Pasture/grassland/range, Good, HSG C
' 9.880 Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
38.0 250 0.0100 0.11 Sheet Flow,
Grass: Dense n= 0.240 P2= 3.40"
' 8.4 1,825 0.0500 3.60 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
46.4 2,075 Total

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' BMP #5 Type// 24-hr Rainfall=2.81"
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008
' Subcatchment 7S: BMP #5 Post-Development
' Runoff = 13.32 cfs @ 12.36 hrs, Volume= 1.546 af, Depth> 1.88"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 1.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr Rainfall=2.81"
Area (ac) CN Description
6.826 98 Paved VDA
3.054 74 >75% Grass cover, Good, HSG C
9.880 91 Weighted Average
3.054 Pervious Area
' 6.826 Impervious Area
Tc Length Slope Velocity Capacity Description
1 (min) (feet) (ft/ft) (ft/sec) (cfs)
18.1 180 0.0330 0.17 Sheet Flow,
Grass. Dense n= 0.240 P2= 3.40"
22.0 1,895 0.0050 1.44 Shallow Concentrated Flow,
' Paved Kv= 20.3 fps
40.1 2,075 Total

n

' BMP #5 Type// 24-hr Rainfall=2.81"
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/17/2008
Pond 8P: BMP #5 Pond Design
Inflow Area 9.880 ac, Inflow Depth > 1.88"
Inflow 13.32 cfs @ 12.36 hrs, Volume= 1.546 of
Outflow = 4.23 cfs @ 12.99 hrs, Volume= 0.990 af, Atten= 68%, Lag= 37.9 min
Primary = 4.23 cfs @ 12.99 hrs, Volume= 0.990 of
' Secondary = 0.00 cfs @ 1.00 hrs, Volume= 0.000 of
Routing by Stor-Ind method, Time Span= 1.00-24.00 hrs, dt= 0.05 hrs
Peak Elev= 126.39'@ 12.99 hrs Surf.Area= 0.431 ac Storage= 0.742 of
Plug-Flow detention time= 185.6 min calculated for 0.988 of (64% of inflow)
Center-of-Mass det. time= 86.8 min ( 917.0 - 830.2 )
' Volume Invert Avail.Storage Storage Description
#1 124.50' 2.464 of Custom Stage Data (Irregular) Listed below (Recalc)
Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area
(feet) (acres) (feet) (acre-feet) (acre-feet) (acres)
' 124.50 0.322 508.0 0.000 0.000 0.322
125.00 0.382 539.0 0.176 0.176 0.382
126.00 0.418 558.0 0.400 0.576 0.422
127.00 0.451 577.0 0.434 1.010 0.463
128.00 0.459 596.0 0.455 1.465 0.506
129.00 0.499 615.0 0.479 1.944 0.550
130.00 0.541 751.0 0.520 2.464 0.890
Device Routing Invert Outlet Devices
#1 Primary 124.50' 12.0" x 86.0' long Culvert RCP, sq.cut end projecting, Ke= 0.500
Outlet Invert= 123.50' S=0.0116'/' Cc= 0.900 n=0.013
#2 Device 1 124.50' 3.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 125.95' 4.00'x 4.00' Horiz. Orifice/Grate Limited to weir flow C= 0.600
#4 Secondary 128.25' 30.0' long x 10.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=4.23 cfs @ 12.99 hrs HW=126.39' (Free Discharge)
t-1=Culvert (Barrel Controls 4.23 cfs @ 5.38 fps)
2=Orifice/Grate (Passes < 0.31 cfs potential flow)
L3=Orifice/Grate (Passes < 15.31 cfs potential flow)
Secondary OutFlow Max=0.00 cfs @ 1.00 hrs HW=124.50' (Free Discharge)
t-4=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
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Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/17/2008
Pond 8P: BMP #5 Pond Design
Inflow Area 9.880 ac, Inflow Depth = 0.36"
Inflow 2.38 cfs @ 12.39 hrs, Volume= 0.296 of
Outflow = 0.15 cfs @ 16.83 hrs, Volume= 0.277 af, Atten= 94%, Lag= 266.4 min
Primary = 0.15 cfs @ 16.83 hrs, Volume= 0.277 of
Secondary = 0.00 cfs @ 1.00 hrs, Volume= 0.000 of
Routing by Stor-Ind method, Time Span= 1.00-60.00 hrs, dt= 0.05 hrs
Peak Elev= 125.01'@ 16.83 hrs Surf.Area= 0.382 ac Storage= 0.181 of
Plug-Flow detention time= 722.6 min calculated for 0.277 of (94% of inflow)
Center-of-Mass det. time= 689.9 min ( 1,573.9 - 884.0 )
Volume Invert Avail.Storage Storage Description
#1 124.50' 2.464 of Custom Stage Data (Irregular) Listed below (Recalc)
Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area
(feet) (acres) (feet) (acre-feet) (acre-feet) (acres)
1 124.50 0.322 508.0 0.000 0.000 0.322
125.00 0.382 539.0 0.176 0.176 0.382
126.00 0.418 558.0 0.400 0.576 0.422
127.00 0.451 577.0 0.434 1.010 0.463
128.00 0.459 596.0 0.455 1.465 0.506
129.00 0.499 615.0 0.479 1.944 0.550
130.00 0.541 751.0 0.520 2.464 0.890
I Device Routing Invert Outlet Devices
#1 Primary 124.50' 12.0" x 86.0' long Culvert RCP, sq.cut end projecting, Ke= 0.500
1 Outlet Invert= 123.50' S=0.0116'/' Cc= 0.900 n=0.013
#2 Device 1 124.50' 3.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 125.95' 4.00'x 4.00' Horiz. Orifice/Grate Limited to weir flow C= 0.600
1 #4 Secondary 128.25' 30.0' long x 10.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=0.15 cfs @ 16.83 hrs HW=125.01' (Free Discharge)
t-1=Culvert (Passes 0.15 cfs of 0.99 cfs potential flow)
L2=Orifice/Grate (Orifice Controls 0.15 cfs @ 3.00 fps)
3=Orifice/Grate ( Controls 0.00 cfs)
Secondary OutFlow Max=0.00 cfs @ 1.00 hrs HW=124.50' (Free Discharge)
t-4=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
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WATER QUALITY POND CALCULATIONS
Project Name
NCCAR - BMP #5
Project Number
04921-0003
Date
April 17, 2008
3rd revision
2nd revision
1 st revision

i

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Water Quality Pond Drainage Area Data
Project
Project No.
Date
Total site area
NCCAR - BMP #5
04921-0003
April 17, 2008
430,393 square feet =
acres
Dra inage area to pond Other Drai nage Area

Impervious areas Existing
[sf] Proposed
[sf] Change
[sf] Existing
[sf] Proposed
[sf]
On-site buildings 0 0 0 0 0
On-site streets 0 0 0 0 0
On-site parkin 0 0 0 0 0
On-site sidewalks 0 0 0 0 0
Other on-site 0 297,357 297,357 0 0
Total off-site impervious 0 0 0 0 0
Total Impervious 0 297,357 297,357--- f- 0 0
Drainage area to pond Other Dra inage Area

Non-impervious areas
On-site grass/landscape Existing
[sf]
0 Proposed
[sf]
137,267 Change
[sf]
137,267 Existing
[sf]
0 Proposed
[sf]
0
On-site woods 0 0 0 0 0
Other undeveloped 0 0 0 0 0
Total off-site non-impervious 0 0 0 0 0
Total non-impervious 0 137,267 137,267 0 0
Total Drainage Area 430,393 430,393 0 3,167,850 3,167,850
Percent Impervious 0.0 69.1 69.1 0.0 0.0
Notes:
BMP #5.xls
Site Drainage Area Data
Page 1 of 1
9.88
Printed 4/16/2008 3:27 PM

1
1

Water Quality Pond Surface Area Calculations
Project
Project No
Date
NCCAR - BMP #5
04921-0003
April 17, 2008
Total on-site drainage area to pond 430,393 square feet
Total impervious area in drainage area 297,357 square feet
Average water depth of basin at normal pool 3.0 feet
Location of site
Site region
% Impervious cover
Northampton County
Piedmont
69.1
percent
If the site is in a coastal area, will a vegetative filter be used? n/a
Surface Area/Drainage Area Ratios:
For a site in the Piedmont 2.8 percent
For a site in a Coastal County w/ Vegetative Filter 5.9 percent
For a site in a Coastal County w/out Vegetative Filter 8.0 percent
Required surface area of pond:
For a site in the Piedmont 12,210.0 square feet
For a site in a Coastal County w/ Vegetative Filter 25,440.0 square feet
For a site in a Coastal County w/out Vegetative Filter 34,440.0 square feet
Notes:
BMP #5.xls
Pond Surface Area Calcs
Page 1 of 1
Printed 4/16/2008 3:27 PM
1
1
1
Water Quality Pond Stormwater Runoff Volume Calculations
Project NCCAR -BMP #5
Project No. 04921-0003

Date April 17, 2008

Drainage area 430,393 square feet
Impervious area 297,357 square feet
Rainfall depth 1.00 inches

Percent Impervious 69.1 percent

R(v)=0.05+0.009*(Perce nt impervious)
Runoff coefficient - R(v) 0.67 in/in
Runoff volume=(Design rainfall)*(R(v))*(Drainage area)
Runoff volume 24,095.1 cubic feet
Notes:
BMP #5.xls
Runoff Volume Calcs
Page 1 of 1
Printed 4/16/2008 3:27 PM
t

Water Quality Pond Volume Calculations
Stage-Storage Data for Pond - Temporary Pool
Project NCCAR - BMP #5
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
[s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
124.5 0 14,030.0 0.322 14,030.0 0.3 0.0 0.0 0.0 0.0
125 0.5 16,647.0 0.382 2,617.0 0.1 7,669.3 0.2 7,669.3 0.2
125.95 1.45 18,209.0 0.418 1,562.0 0.0 16,556.6 0.4 24,225.9 0.6
126 1.5 19,651.0 0.451 1,442.0 0.0 946.5 0.0 25,172.4 0.4
127 2.5 19,996.0 0.459 345.0 0.0 19,823.5 0.5 44,995.9 0.5
128 3.5 21,755.0 0.499 1,759.0 0.0 20,875.5 0.5 65,871.4 0.9
129 4.5 23,571.0 0.541 1,816.0 0.0 22,663.0 0.5 88,534.4 1.0
130 5.5 26,148.0 0.600 2,577.0 0.1 24,859.5 0.6 113,393.9 1.1

BMP #5.xls
Stage Storage (Temp Pool)
Page 1 of 1
Printed 4/16/2008 3:27 PM

F

1
1

Water Quality Pond Volume Calculations
Stage-Storage Data for Pond - Permanent Pool
Project NCCAR - BMP #5
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
[s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
118 0 1,912.0 0.044 1,912.0 0.0 0.0 0.0 0.0 0.0
119 1 2,799.0 0.064 887.0 0.0 2,355.5 0.1 2,355.5 0.1
120 2 4,678.0 0.107 1,879.0 0.0 3,738.5 0.1 6,094.0 0.1
121 3 6,045.0 0.139 1,367.0 0.0 5,361.5 0.1 11,455.5 0.2
122 4 7,521.0 0.173 76.0 0.0 6,783.0 0.2 18,238.5 0.3
123 5 9,111.0 0.209 90.0
g 0.0 8,316.0 0.2 26,554.5 0.3
124 6 10,814.0 0.248 03.0 0.0 9,962.5 0.2 36,517.0 0.4
124.5 6.5 14,030.0 0.322 3,216.0 0.1 6,211.0 0.1 42,728.0 0.4

BMP #5.xls
' Stage Storage (Perm Pool) Page 1 of 1 Printed 4/16/2008 3:27 PM

11

1

1

Water Quality Pond Volume Calculations
Stage-Storage Data for Pond - Forebay
Project NCCAR - BMP #5
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
120 0 941.0 0.022 941.0 0.0 0.0 0.0 0.0 0.0
121 1 1,310.0 0.030 369.0 0.0 1,125.5 0.0 1,125.5 0.0
122 2 1,735.0 0.040 425.0 0.0 1,522.5 0.0 2,648.0 0.1
123 3 2,217.0 0.051 482.0 0.0 1,976.0 0.0 4,624.0 0.1
124 4 2,756.0 0.063 539.0 0.0 2,486.5 0.1 7,110.5 0.1
124.5 4.5 3,832.0 0.088 1,076.0 0.0 1,647.0 0.0 8,757.5 0.1

BMP #5.xls
Stage Storage (Forebay) Page 1 of 1 Printed 4/16/2008 3:27 PM
f

1
1
Water Quality Basin Dewatering Time Calculations
Project NCCAR - BMP #5
Project No. 04921-0003
Date April 17, 2008
Maximum surface area of basin 18,209.0 square feet
Maximum head of water above dewatering hole 1.45 feet
Orifice coefficient 0.60
Diameter of each hole 3.0 inches
Number of holes 1
Cross sectional area of each hole =
Cross sectional area of each hole =
Cross sectional area of dewatering hole(s) _
Cross sectional area of dewatering hole(s) _
Dewatering time for basin =
Dewatering time for basin =
Notes:
0.049 square feet
7.1 square inches
0.049 square feet
7.1 square inches
51.5 hours
2.1 days
1
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Water Quality Pond Summary Information
Project NCCAR - BMP #5
Project No. 04921-0003
Date April 17, 2008
Drainage area to pond 430,393 square feet =
Impervious area in drainage area 297,357 square feet =
Bottom of pond elevation 120.00 feet
Normal pool elevation 124.50 feet
Pond volume at normal pool 38,431 cubic feet
9.88 acres
6.83 acres
Required volume for design rainfall 24,095 cubic feet
Required surface area for pond 12,210 square feet
Volume provided for storage of design rainfall = 24,226 cubic feet at elevation 125.95
Surface area provided at normal pool 14,030 square feet
BMP #5.xls
Summary Data
Page 1 of 1
Printed 4/16/2008 3:28 PM
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DESIGN PHASE
..: fib :.: wn+n:v.vn•:::: ?i :•:::: n:.:......
:xF..: rn:v::: n•:::;.+.::i: n:vv: n•n.:: r:.:::•i:•ii:•iii:•:i•$ii:4:tf:::::•:t:•,?jig:•,::,::::i:.'•:??:ii::::+iii?:

04/21/08

PRELIM

PROJECT NAME PROJECT NO CONSTR
NCCAR 4921-0003 REVISION
LOCATION BY RECORD
Garysburg, NC GCA OTHER
BMP #5 CHECKED BY (SPECIFY)
GML
Storm Outlet Structure
Structure= BMP #5
Size= 12 in
Q1o = 6.08 cfs
Qfull = 3.83 cfs
Vfull = 4.88 fps
From Fig. 8.06.b.1:
From Fig. 8.06.b.2:
Q1o/Qfull = 1.59
VNfull = 1.59
V = 7.7 fps
Zone = 2
D5o = 8 in
DMAx = 12 in
Riprap Class = B
Apron Thickness = 12 in
Apron Length = 6.0 ft
Apron Width = 3xDia = 3 ft
0
' BMP #6 Type 1124-hr Rainfall=2.81"
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008
Subcatchment 1S: BMP #6 - Pre-Development
' Runoff = 8.45 cfs @ 12.99 hrs, Volume= 1.809 af, Depth> 0.77"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 2.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr Rainfall=2.81"
' Area (ac) CN Description
28.330 74 Pasture/grassland/range, Good, HSG C
' 28.330 Pervious Area
Tc Length Slope Velocity Capacity Description
' (min) (feet) (ft/ft) (ft/sec) (cfs)
43.9 250 0.0070 0.10 Sheet Flow,
Grass: Dense n= 0.240 P2= 3.40"
' 36.7 3,025 0.0073 1.38 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
80.6 3,275 Total

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BMP #6 Type// 24-hr Rainfall=2.81"
Prepared by McKim & Creed, PA
HydroCADO 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008
i Subcatchment 2S: BMP #6 - Post-development
Runoff = 30.62 cfs @ 12.66 hrs, Volume= 5.045 af, Depth> 2.14"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 2.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr Rainfall=2.81"
Area (ac) CN Description
24.080 98 Paved parking & roofs
4.250 74 >75% Grass cover, Good, HSG C
28.330 94 Weighted Average
4.250 Pervious Area
24.080 Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
' 30.5 300 0.0250 0.16 Sheet Flow,
Grass: Dense n= 0.240 P2= 3.40"
34.5 2,975 0.0050 1.44 Shallow Concentrated Flow,
' Paved Kv= 20.3 fps
65.0 3,275 Total

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' BMP #6
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC Type// 24-hr Rainfall=2.81"

4/16/2008
Pond 3P: BMP #6 - Pond Design
Inflow Area 28.330 ac, Inflow Depth > 2.14"
Inflow 30.62 cfs @ 12.66 hrs, Volume=
5.045 of
Outflow = 6.62 cfs @ 14.00 hrs, Volume= 3.097 af, Atten= 78%, Lag= 80.7 min
Primary = 6.62 cfs @ 14.00 hrs, Volume= 3.097 of
Secondary = 0.00 cfs @ 2.00 hrs, Volume= 0.000 of
Routing by Stor-Ind method, Time Span= 2.00-24.00 hrs, dt= 0.05 hrs
1 Peak Elev= 121.97'@ 14.00 hrs Surf.Area= 1.261 ac Storage= 2.879 of
Plug-Flow detention time= 234.7 min calculated for 3.097 of (61 % of inflow)
Center-of-Mass det. time= 134.8 min ( 968.9 - 834.1 )

Volume Invert Avail.Storage Storage Descrip tion
#1 119.50' 7.035 of Custom Stage Data (Irregular) Listed below (Recalc)

Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area
(feet) (acres) (feet) (acre-feet) (acre-feet) (acres)
119.50 1.011 962.0 0.000 0.000 1.011
120.00 1.124 994.0 0.534 0.534 1.126
121.00 1.193 1,013.0 1.158 1.692 1.199
' 122.00 1.263 1,031.0 1.228
123.00 1.335 1,050.0 1.299 2.920
4.218 1.270
1.347
124.00 1.408 1,069.0 1.371 5.590 1.424
125.00 1.482 1,088.0 1.445 7.035 1.503
1 Device Routina Invert Outlet Devices
#1 Primary 117.70' 12.0" x 58.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 117.30' S=0.0069'/' Cc= 0.900 n=0.013
#2 Device 1 119.50' 5.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 121.20' 4.00'x 4.00' Horiz. Orifice/Grate Limited to weir flow C= 0.600
#4 Secondary 123.40' 30.0' long x 10.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=6.62 cfs @ 14.00 hrs HW=121.97' (Free Discharge)
t1=Culvert (Barrel Controls 6.62 cfs @ 8.43 fps)
2=Orifice/Grate (Passes < 0.99 cfs potential flow)
L
' 3=Orifice/Grate (Passes < 35.17 cfs potential flow)
Secondary OutFlow Max=0.00 cfs @ 2.00 hrs HW=119.50' (Free Discharge)
t4=Broad-Crested Rectangular Weir (Controls 0.00 cfs)

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BMP #6
Type 1124-hr Rainfall=1.00"
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008
Pond 3P: BMP #6 - Pond Design
Inflow Area = 28.330 ac, Inflow Depth = 0.50"
Inflow = 7.11 cfs @ 12.69 hrs, Volume= 1.189 of
Outflow = 0.48 cfs @ 17.83 hrs, Volume= 1.045 af, Atten= 93%, Lag= 308.2 min
Primary = 0.48 cfs @ 17.83 hrs, Volume= 1.045 of
Secondary = 0.00 cfs @ 2.00 hrs, Volume= 0.000 of
Routing by Stor-Ind method, Time Span= 2.00-60.00 hrs, dt= 0.05 hrs
Peak Elev= 120.24'@ 17.83 hrs Surf.Area= 1.140 ac Storage= 0.804 of
Plug-Flow detention time= 893.0 min calculated for 1.044 of (88% of inflow)
Center-of-Mass det. time= 834.8 min ( 1,719.1 - 884.3 )
Volume Invert Avail.Storage Storage Description
#1 119.50' 7.035 of Custom Stage Data (Irregular) Listed below (Recalc)
Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area
(feet) (acres) (feet) (acre-feet) (acre-feet) (acres)
119.50 1.011 962.0 0.000 0.000 1.011
120.00 1.124 994.0 0.534 0.534 1.126
121.00 1.193 1,013.0 1.158 1.692 1.199
122.00 1.263 1,031.0 1.228 2.920 1.270
123.00 1.335 1,050.0 1.299 4.218 1.347
124.00 1.408 1,069.0 1.371 5.590 1.424
125.00 1.482 1,088.0 1.445 7.035 1.503
Device Routing Invert Outlet Devices
#1 Primary 117.70' 12.0" x 58.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 117.30' S= 0.0069T Cc= 0.900 n= 0.013
#2 Device 1 119.50' 5.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 121.20' 4.00'x 4.00' Horiz. Orifice/Grate Limited to weir flow C= 0.600
#4 Secondary 123.40' 30.0' long x 10.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=0.48 cfs @ 17.83 hrs HW=120.24' (Free Discharge)
t-1=Culvert (Passes 0.48 cfs of 4.82 cfs potential flow)
?__3=Orifice/G 2=Orifice/G rate (Orifice Controls 0.48 cfs @ 3.51 fps)
rate ( Controls 0.00 cfs)
Secondary OutFlow Max=0.00 cfs @ 2.00 hrs HW=119.50' (Free Discharge)
L4=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
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WATER QUALITY POND CALCULATIONS
Project Name
NCCAR - BMP #6
Project Number
04921-0003
Date
April 17, 2008
3rd revision
2nd revision
1 st revision
Water Quality Pond Drainage Area Data

Project
Project No.
Date
NCCAR -BMP #6
Total site area
04921-0003
April 17, 2008
1,233,932 square feet =
28.33 acres
1
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Drai nage area to pond Other Drai nage Area

Impervious areas Existing
[sf] Proposed
s Change
s Existing
[sf] Proposed
[s
On-site buildings 0 0 0 0 0
On-site streets 0 0 0 0 0
On-site parking 0 0 0 0 0
On-site sidewalks 0 0 0 0 0
Other on-site 0 1,048,845 1,048,845 0 0
Total off-site impervious 0 0 0 0 0
Total impervious 0 1,048,845 1,048,845 0 0
Dra inage area to pond Other Drai nage Area

Non-impervious areas Existing
[sf] Proposed
[sf] Change
[s Existing
[sf] Proposed
[sf]
On-site grass/landscape 0 137,267 137,267 0 0
On-site woods 0 0 0 0 0
Other undeveloped 0 0 0 0 0
Total off-site non-impervious 0 0 0 0 0
Total non-impervious 0 137,267 137,267 0 0
Total Drainage Area 1,233,932 1,233,932 0 3,167,850 3,167,850
Percent Impervious 0.0 85.0 85.0 0.0 0.0
Notes:
BMP #6.xls
Site Drainage Area Data
Page 1 of 1
Printed 4/16/2008 3:36 PM

1
Water Quality Pond Surface Area Calculations
Project
Project No
Date
NCCAR - BMP #6
04921-0003
April 17, 2008
Total on-site drainage area to pond 1,233,932 square feet
Total impervious area in drainage area 1,048,845 square feet
Average water depth of basin at normal pool 3.0 feet
Location of site Northampton County
Site region Piedmont
% Impervious cover 85.0 percent
If the site is in a coastal area, will a vegetative filter be used? n/a
Surface Area/Drainage Area Ratios:
For a site in the Piedmont 3.6 percent
For a site in a Coastal County w/ Vegetative Filter 7.2 percent
For a site in a Coastal County w/out Vegetative Filter 10.1 percent
Required surface area of pond:
For a site in the Piedmont 43,810.0 square feet
For a site in a Coastal County w/ Vegetative Filter 88,230.0 square feet
For a site in a Coastal County w/out Vegetative Filter 124,020.0 square feet
Notes:
BMP #6.xls
Pond Surface Area Calcs
Page 1 of 1
Printed 4/16/2008 3:36 PM
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Water Quality Pond Stormwater Runoff Volume Calculations
Project NCCAR - BMP #6
Project No. 04921-0003

Date April 17, 2008

Drainage area 1,233,932 square feet
Impervious area 1,048,845 square feet
Rainfall depth 1.00 inches

Percent Impervious 85.0 percent

R(v)=0.05+0.009*(Perce nt impervious)
Runoff coefficient - R(v) 0.82 in/in
Runoff volume=(Design rainfall)*(R(v))*(Drainage area)
Runoff volume 83,804.8 cubic feet
Notes:
BMP #6.xls
Runoff Volume Calcs Page 1 of 1
Printed 4/16/2008 3:36 PM
11

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1

Water Quality Pond Volume Calculations
Stage-Storage Data for Pond - Temporary Pool
Project NCCAR - BMP #6
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
[s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
119.5 0 44,048.0 1.011 44,048.0 1.0 0.0 0.0 0.0 0.0
120 0.5 48,940.0 1.124 4,892.0 0.1 23,247.0 0.5 23,247.0 0.5
121 1.5 51,952.0 1.193 3,012.0 0.1 50,446.0 1.2 73,693.0 1.7
121.2 1.7 52,561.0 1.207 609.0 0.0 10,451.3 0.2 84,144.3 1.4
122 2.5 55,018.0 1.263 2,457.0 0.1 43,031.6 1.0 127,175.9 1.2
123 3.5 58,142.0 1.335 3,124.0 0.1 56,580.0 1.3 183,755.9 2.3
124 4.5 61,323.0 1.408 3,181.0 0.1 59,732.5 1.4 243,488.4 2.7
125 5.5 64,560.0 1.482 3,237.0 0.1 62,941.5 1.4 306,429.9 2.8

BMP #6.xls
Stage Storage (Temp Pool) Page 1 of 1 Printed 4/16/2008 3:36 PM

11

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I
Water Quality Pond Volume Calculations
Stage-Storage Data for Pond -Permanent Pool
Project NCCAR -BMP #6
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
[s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
113 0 14,648.0 0.336 14,648.0 0.3 0.0 0.0 0.0 0.0
114 1 16,467.0 0.378 1,819.0 0.0 15,557.5 0.4 15,557.5 0.4
115 2 18,343.0 0.421 1,876.0 0.0 17,405.0 0.4 32,962.5 0.8
116 3 28,480.0 0.654 10,137.0 0.2 23,411.5 0.5 56,374.0 0.9
117 4 31,677.0 0.727 3,197.0 0.1 30,078.5 0.7 86,452.5 1.2
118 5 34,987.0 0.803 3,310.0 0.1 33,332.0 0.8 119,784.5 1.5
119 6 38,522.0 0.884 3,535.0 0.1 36,754.5 0.8 156,539.0 1.6
119.5 6.5 44,048.0 1.011 5,526.0 0.1 20,642.5 0.5 177,181.5 1.3

BMP #6.xls
Stage Storage (Perm Pool) Page 1 of 1 Printed 4/16/2008 3:37 PM

1

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Water Quality Pond Volume Calculations
Stage-Storage Data for Pond - Forebay
Project NCCAR - BMP #6
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
[s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
116 0 8,204.0 0.188 8,204.0 0.2 0.0 0.0 0.0 0.0
117 1 9,412.0 0.216 1,208.0 0.0 8,808.0 0.2 8,808.0 0.2
118 2 10,677.0 0.245 1,265.0 0.0 10,044.5 0.2 18,852.5 0.4
119 3 11,998.0 0.275 1,321.0 0.0 11,337.5 0.3 30,190.0 0.5
119.5 3.5 14,138.0 0.325 2,140.0 0.0 6,534.0 0.2 36, 724.0 0.4

BMP #6.xls
Stage Storage (Forebay) Page 1 of 1 Printed 4/16/2008 3:37 PM
Water Quality Basin Dewatering Time Calculations
Project NCCAR - BMP #6
Project No. 04921-0003
Date April 17, 2008
Maximum surface area of basin
Maximum head of water above dewatering hole
Orifice coefficient
Diameter of each hole
Number of holes
Cross sectional area of each hole =
Cross sectional area of each hole =
Cross sectional area of dewatering hole(s) _
Cross sectional area of dewatering hole(s) _
Dewatering time for basin =
Dewatering time for basin =
52,561 square feet
1.7 feet
5.0 inches
0.136 square feet
19.6 square inches
0.136 square feet
19.6 square inches
58.0 hours
2.4 days
Notes:
i

Water Quality Pond Summary Information
Project NCCAR - BMP #6
Project No. 04921-0003
Date April 17, 2008
Drainage area to pond 1,233,932 square feet =
Impervious area in drainage area 1,048,845 square feet =
Bottom of pond elevation 114.00 feet
Normal pool elevation 119.50 feet
Pond volume at normal pool 161,540 cubic feet
28.33 acres
24.08 acres
Required volume for design rainfall 83,805 cubic feet
Required surface area for pond 43,810 square feet
Volume provided for storage of design rainfall = 84,717 cubic feet at elevation
Surface area provided at normal pool 44,048 square feet
BMP #6.xls
Summary Data
Page 1 of 1
121.4
Printed 4/16/2008 3:37 PM
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.::.,.:::::::::,,{,::,::?.::::^::::i:.i:.ii:.>:.ii{:.... ...>....»> .. r.::•?>?»:::::>::::;:;:?;:>;::::: 04/21/08 PRELIM
PROJECT NAME PROJECT NO CONSTR
NCCAR 4921-0003 REVISION
LOCATION BY RECORD
Ga sburg, NC GCA OTHER
BMP #6 CHECKED BY (SPECIFY)
GML
Storm Outlet Structure
Structure= BMP #6
Size= 12 in
Q1o = 8.40 cfs
Qfull = 2.95 cfs
Vfull = 7.02 fps
From Fig. 8.06.b.1:
From Fig. 8.06.b.2:
Quo/Qfull = 2.85
V/Vfull = 1.52
V = 10.7 fps
Zone = 2
D5o = 8 in
DMAx = 12 in
Riprap Class = B
Apron Thickness = 12 in
Apron Length = 6.0 ft
Apron Width = 3xDia = 3 ft
1
' BMP #7 Type// 24-hr Rainfall=2.81"
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008
' Subcatchment 1S: BMP #7 - Pre-deviopment
' Runoff = 6.01 cfs @ 12.57 hrs, Volume= 0.934 af, Depth> 0.78"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 2.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr Rainfall=2.81"
Area (ac) CN Description
14.460 74 Pasture/grassland/range, Good, HSG C
' 14.460 Pervious Area
Tc Length Slope Velocity Capacity Description
' (min) (feet) (ft/ft) (ft/sec) (cfs)
32.3 250 0.0150 0.13 Sheet Flow,
Grass: Dense n= 0.240 P2= 3.40"
' 19.1 2,100 0.0130 1.84 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
51.4 2,350 Total

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BMP #7 Type 11 24-hr Rainfall=2.81"
Prepared by McKim & Creed, PA
HydroCADO 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008
' Subcatchment 2S: BMP #7 - Post-development
' Runoff = 20.90 cfs @ 12.36 hrs, Volume= 2.476 af, Depth> 2.05"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 2.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr Rainfall=2.81"

0

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Area (ac) CN Description
11.370 98 Paved parking & roofs
3.090 74 >75% Grass cover, Good, HSG C
14.460 93 Weighted Average
3.090 Pervious Area
11.370 Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
15.5 175 0.0460 0.19 Sheet Flow,
Grass: Dense n= 0.240 P2= 3.40"
25.3 2,175 0.0050 1.44 Shallow Concentrated Flow,
Paved Kv= 20.3 fas
40.8 2,350 Total
1
BMP #7 Type 1124-hr Rainfall=2.81"
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008
Pond 3P: BMP #3 - Pond Design
Inflow Area = 14.460 ac, Inflow Depth > 2.05"
Inflow = 20.90 cfs @ 12.36 hrs, Volume= 2.476 of
Outflow = 5.90 cfs @ 13.06 hrs, Volume= 1.508 af, Atten= 72%, Lag= 41.9 min
Primary = 5.90 cfs @ 13.06 hrs, Volume= 1.508 of
Secondary = 0.00 cfs @ 2.00 hrs, Volume= 0.000 of
Routing by Stor-Ind method, Time Span= 2.00-24.00 hrs, dt= 0.05 hrs
Peak Elev= 125.77'@ 13.06 hrs Surf.Area= 0.648 ac Storage= 1.333 of
Plug-Flow detention time= 219.8 min calculated for 1.504 of (61 % of inflow)
Center-of-Mass det. time= 119.5 min ( 940.2 - 820.7 )
Volume Invert Avail.Storage Storage Description
#1 123.50' 3.335 of Custom Stage Data (Irregular) Listed below (Recalc)
Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area
(feet) (acres) (feet) (acre-feet) (acre-feet) (acres)
123.50 0.490 635.0 0.000 0.000 0.490
124.00 0.565 666.0 0.264 0.264 0.564
125.00 0.611 685.0 0.588 0.851 0.613
126.00 0.659 704.0 0.635 1.486 0.664
127.00 0.708 723.0 0.683 2.170 0.716
128.00 0.802 815.0 0.755 2.924 0.975
128.50 0.841 921.0 0.411 3.335 1.312
Device Routing Invert Outlet Devices
#1 Primary 120.50' 30.0" x 63.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 120.00' S= 0.0079 '/' Cc= 0.900 n=0.013
#2 Device 1 123.50' 3.5" Vert. Orifice/Grate C= 0.600
#3 Device 1 125.15' 3.50'W x 3.50' H Vert. Orifice/Grate C= 0.600
#4 Secondary 127.40' 30.0' long x 10.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=5.89 cfs @ 13.06 hrs HW=125.77' (Free Discharge)
L1=Culvert (Passes 5.89 cfs of 47.36 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.47 cfs @ 7.01 fps)
L3=Orifice/Grate (Orifice Controls 5.42 cfs @ 2.52 fps)
Secondary OutFlow Max=0.00 cfs @ 2.00 hrs HW=123.50' (Free Discharge)
t-4=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
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BMp #7 Type// 24-hr Rainfall=1.00"
Prepared by McKim & Creed, PA
HydroCAD® 8.00 s/n 004927 © 2006 HydroCAD Software Solutions LLC 4/16/2008
Pond 3P: BMP #3 - Pond Design
Inflow Area = 14.460 ac, Inflow Depth = 0.45"
Inflow 4.49 cfs @ 12.39 hrs, Volume= 0.543 of
Outflow 0.23 cfs @ 17.35 hrs, Volume= 0.497 af, Atten= 95%, Lag= 297.7 min
Primary = 0.23 cfs @ 17.35 hrs, Volume= 0.497 of
Secondary = 0.00 cfs @ 2.00 hrs, Volume= 0.000 of
Routing by Stor-Ind method, Time Span= 2.00-60.00 hrs, dt= 0.05 hrs
Peak Elev= 124.16'@ 17.35 hrs Surf.Area= 0.572 ac Storage= 0.356 of
Plug-Flow detention time= 846.0 min calculated for 0.497 of (92% of inflow)
Center-of-Mass det. time= 803.3 min ( 1,673.1 - 869.9 )
Volume Invert Avail.Storage Storage Description
#1 123.50' 3.335 of Custom Stage Data (Irregular) Listed below (Recalc)
Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area
(feet) (acres) (feet) (acre-feet) (acre-feet) (acres)
123.50 0.490 635.0 0.000 0.000 0.490
124.00 0.565 666.0 0.264 0.264 0.564
125.00 0.611 685.0 0.588 0.851 0.613
126.00 0.659 704.0 0.635 1.486 0.664
127.00 0.708 723.0 0.683 2.170, 0.716
128.00 0.802 815.0 0.755 2.924 0.975
128.50 0.841 921.0 0.411 3.335 1.312
Device Routing Invert Outlet Devices
#1 Primary 120.50' 30.0" x 63.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 120.00' S=0.0079'/' Cc= 0.900 n=0.013
#2 Device 1 123.50' 3.5" Vert. Orifice/Grate C= 0.600
#3 Device 1 125.15' 3.50'W x 3.50' H Vert. Orifice/Grate C= 0.600
#4 Secondary 127.40' 30.0' long x 10.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=0.23 cfs @ 17.35 hrs HW=124.16' (Free Discharge)
t1=Culvert (Passes 0.23 cfs of 35.20 cfs potential flow)
?__3=Oriflce/G 2=Orifice/G rate (Orifice Controls 0.23 cfs @ 3.46 fps)
rate ( Controls 0.00 cfs)
Secondary OutFlow Max=0.00 cfs @ 2.00 hrs HW=123.50' (Free Discharge)
t4=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)

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WATER QUALITY POND CALCULATIONS
Project Name
BMP #7
Project Number
04921-0003
Date
April 17, 2008
3rd revision
2nd revision
1 st revision
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Water Quality Pond Drainage Area Data
Project BMP #7
Project No. 04921-0003
Date April 17, 2008
Total site area 630,043 square feet = 14.46 acres
Drai nage area to pond Other Drai nage Area

Impervious areas Existing
sf] Proposed
[sf] Change
[s Existing
s Proposed
sf]
On-site buildings 0 0 0 0 0
On-site streets 0 0 0 0 0
On-site parkin 0 0 0 0 0
On-site sidewalks 0 0 0 0 0
Other on-site 0 495,265 495,265 0 0
Total off-site impervious 0 0 0 0 0
Total Impervious 0 495,265 495,265 0 0
Drai nage area to pond Other Drai nage Area

Non-impervious areas Existing
[sf] Proposed
[sf] Change
[s Existing
[sf] Proposed
[sf]
On-site grass/landscape 0 137,267 137,267 0 0
On-site woods 0 0 0 0 0
Other undeveloped 0 0 0 0 0
Total off-site non-impervious 0 0 0 0 0
Total non-impervious 0 137,267 137,267 0 0
Total Drainage Area 630,043 630,043 0 3,167,850 3,167,850
Percent impervious 0.0 78.6 78.6 0.0 0.0
Notes:
BMP #7.xls
Site Drainage Area Data
Page 1 of 1
Printed 4/16/2008 3:41 PM
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Water Quality Pond Surface Area Calculations
Project
Project No
Date
BMP #7
04921-0003
April 17, 2008
Total on-site drainage area to pond 630,043 square feet
Total impervious area in drainage area 495,265 square feet
Average water depth of basin at normal pool 3.0 feet
Location of site Northampton County
Site region Piedmont
% Impervious cover 78.6 percent
If the site is in a coastal area, will a vegetative filter be used? n/a
Surface Area/Drainage Area Ratios:
For a site in the Piedmont 3.3 percent
For a site in a Coastal County w/ Vegetative Filter 6.7 percent
For a site in a Coastal County w/out Vegetative Filter 9.2 percent
Required surface area of pond:
For a site in the Piedmont 20,750.0 square feet
For a site in a Coastal County w/ Vegetative Filter 42,150.0 square feet
For a site in a Coastal County w/out Vegetative Filter 58,090.0 square feet
Notes:
BMP #7.xls
Pond Surface Area Calcs
Page 1 of 1
Printed 4/16/2008 3:41 PM
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Water Quality Pond Stormwater Runoff Volume Calculations
Project BMP #7
Project No. 04921-0003

Date April 17, 2008

Drainage area 630,043 square feet
Impervious area 495,265 square feet
Rainfall depth 1.00 inches

Percent Impervious 78.6 percent

R(v)=0.05+0.009*(Perce nt impervious)
Runoff coefficient - R(v) 0.76 in/in
Runoff volume=(Design rainfall)*(R(v))*(Drainage area)
Runoff volume 39,770.1 cubic feet
Notes:
BMP #7.xls
Runoff Volume Calcs Page 1 of 1
Printed 4/16/2008 3:41 PM
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Water Quality Pond Volume Calculations
Stage-Storage Data for Pond -Temporary Pool
Project BMP #7
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
[s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
123.5 0 21,345.0 0.490 21,345.0 0.5 0.0 0.0 0.0 0.0
124 0.5 24,597.0 0.565 3,252.0 0.1 11,485.5 0.3 11,485.5 0.3
125 1.5 26,624.0 0.611 2,027.0 0.0 25,610.5 0.6 37,096.0 0.9
125.15 1.65 26,933.0 0.618 309.0 0.0 4,016.8 0.1 41,112.8 0.7
126 2.5 28,707.0 0.659 1,774.0 0.0 23,647.0 0.5 64,759.8 0.6
127 3.5 30,847.0 0.708 2,140.0 0.0 29,777.0 0.7 94,536.8 1.2
128 4.5 34,941.0 0.802 4,094.0 0.1 32,894.0 0.8 127,430.8 1.4
128.5 5 36,638.0 0.841 1,697.0 0.0 17,894.8 0.4 145,325.5 1.2

BMP #7.xls
Stage Storage (Temp Pool) Page 1 of 1 Printed 4/16/2008 3:41 PM
Water Quality Pond Volume Calculations
Stage-Storage Data for Pond - Permanent Pool
Project BMP #7
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
[s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
118 0 5,966.0 0.137 5,966.0 0.1 0.0 0.0 0.0 0.0
119 1 7,169.0 0.165 1,203.0 0.0 6,567.5 0.2 6,567.5 0.2
120 2 10,249.0 0.235 3,080.0 0.1 8,709.0 0.2 15,276.5 0.4
121 3 12,349.0 0.283 2,100.0 0.0 11,299.0 0.3 26,575.5 0.5
122 4 14,617.0 0.336 2,268.0 0.1 13,483.0 0.3 40,058.5 0.6
123 5 17,055.0 0.392 2,438.0 0.1 15,836.0 0.4 55,894.5 0.7
123.5 5.5 21,345.0 0.490 4,290.0 0.1 9,600.0 0.2 65,494.5 0.6

BMP #7.xls
Stage Storage (Perm Pool) Page 1 of 1 Printed 4/16/2008 3:41 PM

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Water Quality Pond Volume Calculations
Stage-Storage Data for Pond - Forebays
Project BMP #7
Project No. 04921-0003
Date April 17, 2008

Contour ID
Stage
Area
[s q. ft.
Area
acres Incremental
Area
[s q. ft. Incremental
Area
acres Incremental
volume
cu. ft Incremental
volume
acre-ft Cumulative
volume
cu. ft Cumulative
volume
acre-ft
120 0 1,820.0 0.042 1,820.0 0.0 0.0 0.0 0.0 0.0
121 1 2,603.0 0.060 783.0 0.0 2,211.5 0.1 2,211.5 0.1
122 2 3,498.0 0.080 895.0 0.0 3,050.5 0.1 5,262.0 0.1
123 3 4,506.0 0.103 1,008.0 0.0 4,002.0 0.1 9,264.0 0.2
123.5 3.5 6,437.0 0.148 1,931.0 0.0 2,735.8 0.1 11,999.8 0.2

BMP #7.xls
Stage Storage (Forebays) Page 1 of 1 Printed 4/16/2008 3:41 PM
Water Quality Basin Dewatering Time Calculations
Project BMP #7
Project No. 04921-0003
Date April 17, 2008
Maximum surface area of basin 26,933 square feet
Maximum head of water above dewatering hole 1.7 feet
Orifice coefficient 0.60
Diameter of each hole 3.5 inches
Number of holes 1
Cross sectional area of each hole =
Cross sectional area of each hole =
Cross sectional area of dewatering hole(s) _
Cross sectional area of dewatering hole(s) _
Dewatering time for basin =
Dewatering time for basin =
0.067 square feet
9.6 square inches
0.067 square feet
9.6 square inches
59.7 hours
2.5 days
Notes:
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Water Quality Pond Summary Information
Project BMP #7
Project No. 04921-0003
Date April 17, 2008
Drainage area to pond 630,043 square feet = 14.46 acres
Impervious area in drainage area 495,265 square feet = 11.37 acres
Bottom of pond elevation 119.00 feet
Normal pool elevation 123.50 feet
Pond volume at normal pool 58,927 cubic feet

Required volume for design rainfall 39,770 cubic feet
Required surface area for pond 20,750 square feet
Volume provided for storage of design rainfall = 41,113 cubic feet at elevation 125.15
Surface area provided at normal pool 21,345 square feet
BMP #7.xls
Summary Data
Page 1 of 1
Printed 4/16/2008 3:41 PM
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........:::::::• 04/21/08 PRELIM
PROJECT NAME PROJECT NO CONSTR
NCCAR 4921-0003 REVISION
LOCATION BY RECORD
Garysburg, NC
I GCA OTHER
BMP #7 CHECKED BY (SPECIFY)
GML
Storm Outlet Structure
Structure= BMP #7
Size= 30 in
Q10 = 26.61 cfs
Qfull = 36.40 cfs
Vfull = 7.41 fps
From Fig. 8.06.b.1:
From Fig. 8.06.b.2:
Q1o/Qfull = 0.73
V/Vfull = 0.73
V = 5.4 fps
Zone = 2
D50 = 8 in
DMAx = 12 in
Riprap Class = B
Apron Thickness = 12 in
Apron Length = 15.0 ft
Apron Width = 3xDia = 7.5 ft