20061052 Ver 2_More Info Received_20081030

N
972 Trinity Road
Raleigh, North Carolina 27607
Transmittal
Date: 10/29/08
uaw
TEL [phone]
O C 3 0 2008 FAX [phone]
DE11R . WATER UUALIV
WETLANDS AND STORMWATER BRANCH
Job. No: 576-o5
To: DWQ-4o10versight/Express Review Permitting Unit
165o Mail Service Center - 2121 Cf-A&Vff %LVt?.
Raleigh North Carolina 2769Q-165o
Attn: Cvndi Karoly
Re: Surin2hill Subdivision (DWQ Proiect #o6-1052 Ver 2)
Sending:
® Attached ? Under separate cover the following
via items:
® Prints/Plans ? Shop Drawings ? Specifications ? Samples
® other:
Copies Date Description
10/29/08 Response to R uest for More Information
9/24/o8 DW Request for More Information
10/2g/o8 Drainage Area & BMP Calculations
10/29/o8 Master Drainage Area & Stormwater Management Plans

Transmitted for:
? Your use ? Approved as submitted ? Resubmit ? Copies for approval
? As requested ? Approved as noted ? Submit ? Copies for distribution
® Review and comment ? Returned for ? Return ? Corrected prints
Remarks Per youre request dated September 24, 2oo8, the above referenced documents
arp being submitted for vn1?r review anal annmyal of the rpnnPCted wetland and ctmam imparts
amnmated with the cnhipet nmiprt_ If ynn havp„aLlygnPCtinnc nr nPpd additional information-
nlPASP do not hPRitatp to eantart mp. Thank vnn for your assistanrp with this nmiw t.
Covv to:
L. Norris, PE
SPAULDING & NORRIS, PA
kJN1 Planning ? Civil Engineering ? Environmental
' October 29, 2008
' Cyndi Karolyiti
DWQ401 Oversight/Express Review Permitting Unit
1650 Mail Service Center 0 p ?OpB
' Raleigh, North Carolina 27699-1650 AN QUALIAN V'?.T?NDSAPIDSI?MWA?'RBP.,&NDtI
' RE: Springhill Subdivision (DWQ Project #06-1052, Ver 2)
Response to Request for More Information
' Dear Cyndi,
The following information is provided for the above referenced project in response to a
' DWQ Request for More Information dated September 24, 2008. A copy of this Request
letter has been provided for your convenience. Enclosed for your review and approval are
Drainage Area and BMP Calculations and Maps. Per our correspondence with Amy
' Chapman, the submittal deadline was extended to November 7, 2008.
' Response:
1. Drainage areas and impervious percentages have been calculated for each sub-
basin within the project. Please see the enclosed Master Drainage Area Plan,
' which illustrates the drainage area boundaries for each sub-basin along with a
summary of the impervious percentages- for - each area. Based on these
calculations, sub-basins DA-1B and DA-2B will exceed the 24% impervious area
threshold. Wet Detention Ponds, providing 85 percent TSS removal, have been
preliminarily designed and sized for DA-1B and DA-2B. Please see the enclosed
' Stormwater Management Plan and Calculations for these ponds. The Calculations
also include the required BMP Supplement Worksheet.
t If you have any questions or need additional information to complete your review, please
contact me at [phone]. Thank you for your assistance.
' S' cerely,
Step uue L. Norris, PE
Spaulding & Norris, PA
Enclosures
' Phone: [phone] ? Fax [phone] ? 972 Trinity Road ? Raleigh, o
(919) y North Carolina 27607
William G. Ross Jr., Secretary
North Carolina Department of Environment and Natural Resources
Coleen H. Sullins, Director
Division of Water Quality
September 24, 2008
DWQ Project # 06-1052, Ver. 2
Harnett County
CERTIFIED MAIL: RETURN RECEIPT REQUESTED
Springfield Associates, LLC = A Keystone Company
1207 Roseneath Road
Richmond, VA 23230
Subject Property: Springhill Subdivision
Poorhouse Creek [030607,18-17.5, WSIV]
Ut to Indian Branch [030613, 18-20-26-1, WSIV]
REQUEST FOR MORE INFORMATION
Dear Sir or Madam:
On August 12, 2008, the Division of Water Quality (DWQ) received your application dated July
31, 2008, to fill or otherwise impact 0.5454 acres of 404/wetland (0.4932 acres permanent
impact and 0.0522 acres temporary impact) and 87 linear feet of intermittent stream (28 linear
feet permanent impact and 59 linear feet temporary impact) to construct the proposed residential
subdivision at the site. On September 23, 2008, the DWQ received additional information from
you, however, the DWQ has determined that your application remains incomplete and/or
provided inaccurate information as discussed below. The DWQ will require this additional
information in order. to process your application to impact protected wetlands and/or streams on
- the subject property. Therefore, unless we receive five copies of the-additional-information
requested below,,we will place this project on hold as incomplete until we receive this additional
information. If we do not receive the requested information, your project will be formally
returned as incomplete. Please provide the following information so that we may continue to
review your project.
Additional Information Requested:
' 1. The Town of Lillington is not a stormwater certified community (a list of stormwater
certified communities is available at:
hqp://h2o.enr. state.nc.us/ncwetlands/documents/JurisdictionsthatareCertified-S.pdf).
' Therefore, the comment on high density drainage areas from the September 15, 2008
request for more information letter stands:
' All of the drainage areas on this project appear to be well over the threshold of 24 percent
impervious. Per the requirements of GC 3705, this project must comply with Stormwater
Management Plan (SMP) Requirements for Applicants Other Than the North Carolina
Wa` Carolina
401 Oversight/Express Review Permitting-Unit
trrCQlly
' 1650 Mail Service Center, Raleigh, North Carolina 27699-1650 --
2321 Crabtree Boulevard, Suite 250, Raleigh, North Carolina 27604
Phone: [phone] / FAX [phone] / Internet: http://h2o.enr.state.ne.us/ncwetlands
An Equal Opportunity/Affirmative Action Employer - 50% Recycled/10% Post Consumer Paper
QDAT TT nTXTf---' Q, XTnuuTQ DA
Planning • Civil Engineering ? Environmental
DRAINAGE AREA & STORMWATER MANAGEMENT
CALCULATIONS
for
SPRINGHIL SUBDIVISION
LILLINGTON, HARNETT COUNTY, NORTH CAROLINA
Submitted to:
NCDENR - Division of Water Quality
401 Oversight/Express Review Permitting Unit
1650 Mail Service Center
Raleigh, North Carolina 27699-1650
DWQ Project #06-1052, Ver. 2
Prepared for:
Springhill Associates, LLC
1207 Roseneath Road
Richmond, Virginia 23230
Submitted by:
Spaulding & Norris, PA
972 Trinity Road
Raleigh, North Carolina 27607
[phone]
y r ??e
Q
? U
as",'
DATE: October 29, 2008 ----
PROJECT NO.: 576-05
Phone: [phone] • Fax: [phone] •972 Trinity Road • Raleigh, North Carolina 27607
WATER QUALITY POND CALCULATIONS
Drainage area: DA-1A
Project Name
Spring Hill Subdivision
Project Number
DWQ Project# 06-1052, Ver. 2
Date
09-Oct-08
3rd revision
2nd revision
1 st revision

' Water Quality Pond Drainage Area Data
' Project Spring Hill Subdivision
Project No. DWQ Project# 06-1052, Ver. 2
' Date 9-Oct-08
Total site area 467,720 square feet = 10.74 acres

1
1
1
Draina a area to and Other Drai nage Area

Impervious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site buildings 0 67,500 67,500 0 0
On-site streets 0 39,205 39,205 0 0
On-site parking 0 0 0 0 0
On-site sidewalks 0 5,225 5,225 0 0
Other on-site 0 0 0 0 0
Total off-site impervious 0 0 0 0 0
Total Impervious 0 111,930 111,930 0 0
Draina a area to and Other Drai nage Area

Non-impervious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site grass/landscape 0 238,911 238,911 0 0
On-site woods 467,720 116,879 -350,841 0 0
Other undeveloped 0 0 0 0 0
Total off-site non-impervious 0 0 0 0 0
Total non-impervious 467,720 355,790 -111,930 0 0

'
Since the overall Proposed Percent Impervi ous area is below 24% no BMP devise was required and
no futher calculations were required.
DA-1A.xls
Site Drainage Area Data Page ,1?of 1
Total
Drainage Area
467,720
467,720
0
0
0
Percent Impervious 0.0 23.9 23.9 n/a n/a
Notes:
Printed 10/29/2008 3:58 PM
WATER QUALITY POND CALCULATIONS
Drainage area: DA-1B
Project Name
Spring Hill Subdivision
Project Number
DWQ Project# 06-1052, Ver. 2
Date
09-Oct-08
3rd revision
2nd revision
1 st revision

Water Quality Pond Drainage Area Data
Project Spring Hill Subdivision
Project No. DWQ Project# 06-1052, Ver. 2
Date 9-Oct-08
Total site area 182,263 square feet = 4.18 acres
Draina a area to and Other Drainage Area

Impervious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site buildings 0 40,000 40,000 0 0
On-site streets 0 29,208 29,208 0 0
On-site parking 0 0 0 0 0
On-site sidewalks 0 3,067 3,067 0 0
Other on-site 0 0 0 0 0
Total off-site impervious 0 0 0 0 0
Total Impervious 0 72,275 72,275 0 0
Draina a area to and Other Drainage Area

Non-impervious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site grass/landscape 0 87,840 87,840 0 0
On-site woods 182,263 22,148 -160,115 0 0
Other undeveloped 0 0 0 0 0
Total off-site non-impervious 0 0 0 0 0
Total non-impervious 182,263 109,988 -72,275 0 0
Total Drainage Area 182,263 182,263 0 0 0
Percent Impervious 0.0 39.7 39.7 n/a n/a
Notes:
Since the overall Proposed Percent Impervious area is above 24%, design calations are included for
the BMP device.
DA-1 B xIs
Site Drainage Area Data
Page 1 of 1
Printed 10/29/2008 3:26 PM
Water Quality Pond Surface Area Calculations for Wet Ponds
Project Spring ill StS. ",divislo
06-10"2, e`er-. 21
Project No. }'W Pr6ect ft,
Date `9- ct-03
Total on-site drainage area to pond 182,263 square feet
Total impervious area in drainage area 72,275 square feet
Average water depth of basin at normal pool 7.5
Location of site Lillington, NC
Site region Piedmont
% Impervious cover 39.7 percent
If the site is in a coastal area, will a vegetative filter be used?
Surface Area/Drainage Area Ratios:
For a site in the Piedmont 1.3
For a site in a Coastal County w/ Vegetative Filter 0.0
For a site in a Coastal County w/out Vegetative Filter 0.0
Required surface area of pond:
feet
percent
percent
percent
For a site in the Piedmont 2,4_5 ; 0 square feet
For a site in a Coastal County w/ Vegetative Filter 0.0 square feet
For a site in a Coastal County w/out Vegetative Filter 0.0 square feet
Notes:
DA-1 B .xls
Pond SA -Wet Pond Page 1 of 1 Printed 10/29/2008 3:26 PM
V

r Water Quality Pond Stormwater Runoff Volume Calculations
Project Spring Hill Subdivision
Project No. DWQ Project# 06-1052, Ver. 2
r Date 9-Oct-08
Drainage area 182,263 square feet
Impervious area 72,275 square feet
Rainfall depth 1.00 inches
Percent Impervious 39.7 percent
R(v)=0.05+0.009*(Percent impervious)
Runoff coefficient - R(v) 0.41 in/in
Runoff volume=(Design rainfall)*(R(v))*(Drainage area)
r Runoff volume 6,180.1 cubic feet
Notes:
1
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r
r DA-1 B .xls
Runoff Volume Calcs
r
Page 1 of 1 Printed 10/29/2008 3:26 PM
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Water Quality Basin Dewatering Time Calculations
Project , g Hill Subdivision
' Project No. l rci s ?, m10,52, fi r. 2
' Date 09-0ct-08
Surface area of basin 8,733 square feet
Maximum head of water above dewatering hole 2.00 feet
Orifice coefficient 0.60
Diameter of each hole 1.50 inches
' Number of holes 1
Cross sectional area of each hole = 0.012 square feet
Cross sectional area of each hole = 1.8 square inches

Cross sectional area of dewatering hole(s) = 0.012 square feet
' Cross sectional area of dewatering hole(s) = 1,8 square inches

Dewatering time for basin = 116.1 hours
1 Dewatering time for basin = 4.8 days
Calculations based on NC Sediment and Erosion Control Ma nual
' Page 8.07.8
Notes:

' Water Quality Pond Summary Information
Project Spirin Full Subdivision
' Project No. DVV Prc}elt 0 1052, e'er, 2
' Date -:. Ct-08
Drainage area to pond 182,263 square feet = 418 acres
' Impervious area in drainage area 72,275 square feet = 1.66 acres

Bottom of pond elevation 232.00 feet
' Normal pool elevation 238.50 feet
Pond volume at normal pool 13,613 cubic feet
' Required volume for design rainfall 6,180 cubic feet
Required surface area for pond 2,450 square feet
' Volume provided for storage of design rainfall = 14,956 cubic feet at elevation 240.5
Surface area provided at normal pool 5,408 square feet
DA-1 B .xls
Summary Data
Page 1 of 1
cj?
Printed 10/29/2008 3:30 PM
4Mr --Perm"o. --
Y (to be provided by D WQ)
r;FW?r?9
NCDENR a Y
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
' 401 CERTIFICATION APPLICATION FORM
WET DETENTION BASIN SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Pail 111) must be printed, filled out and submitted along with all of the required information.
L PROJECT INFORMATION
Project name Spring Hifl Subdivision
Contact person Thomas J Spaulding
Phone number 919-854-7990
Date 10/9/2008
Drainage area number DA -113
It. DESIGN INFORMATION
Site Characteristics
Drainage area 182,263.00 ftz
Impervious area 72,275.00 ftz
% impervious 39.65 %
Design rainfall depth 1.00 in
Storage Volume: Non-SR Waters
Minimum volume required 6,480.00 ft3
Volume provided 14,956:00 ft3
Storage Volume: SR Waters
1-yr, 24-hr runoff depth in
Pre-development 1-yr, 24-hr runoff ft3
Post-development 1-yr, 24-hr runoff ft3
Minimum volume required ft3
Volume provided ft3
Peak Flow Calculations
1-yr, 24-hr rainfall depth 2.88 in
Rational C, pre-development - 0.20 (unitless) -
Rational C, post-development 0.50 (unitless)
Rainfall intensity:1-yr, 24-hr storm 4.87 in/hr
Pre-development 1-yr, 24-hr peak flow 4.07 ft3/sec
Post-development 1-yr, 24-hr peak flow 10.18 ft3/sec
Pre/Post 1-yr, 24-hr peak flow control 6.11 ft3/sec
Basin Elevations
Basin bottom elevation 232.00 ft
Sediment cleanout elevation 233.00 It
Bottom of shelf elevation 238.00 ft
Permanent pool elevation 238.50 ft
SHWT elevation It
Top of shelf elevation 239.00 ft
Temporary pool elevation 240.50 ft
Form SW401-Wet Detention Basin-Rev. 4 Parts I. & II. Design Summary, Page 1 of 2
--m& Permit No. - --
(to be provided by DWQ)
II. DESIGN INFORMATION
Volume and Surface Area Calculations
SA/DA ratio 1.34 (unitless)
Surface area at the bottom of shelf 3,948.00 ftz
Volume at the bottom of shelf 11,274.00 ft3
Permanent pool, surface area required 2,450.00 ftz
Permanent pool, surface area provided 5,408.00 ftz OF:.
Permanent pool volume 17.213.00 ft3
Average depth for SA/DA tables 3.18 ft OK
' Surface area at the top of shelf 7,068.00 ftz
Volume at the top of shelf 16,732.00 ft3
Forebayvolume 3.600.00 ft3
Forebay % of permanent pool volume 20.91 % OK
' Temporary pool, surface area provided 8,733.00 ftz
Drawdown Calculations
' Treatment volume drawdown time
Treatment volume discharge rate 4.80
0.04 days
ft3/s OK
Pre-development 1-yr, 24-hr discharge 0.04 ft3/s OK
Post-development 1-yr, 24-hr discharge 0.04 ft3/s OK
Additional Information
Diameter of orifice 1.5 in
Design TSS removal 85 %
Basin side slopes 3.00 1 OK
' Vegetated shelf slope 10.00 1 OK
Vegetated shelf width 10.00 ft OK
Length of flowpath to width ratio 5.00 1 OK
Length to width ratio 2.00 1 OK
Trash rack for overflow & orifice? Y (Y or N) OK
Freeboard provided 1.00 ft OK
Vegetated filter provided? Y (Y or N) OK
' Recorded drainage easement provided? Y (Y or N) OK
Capures all runoff at ultimate build-out? Y (Y or N) CK
Drain mechanism for maintenance or emergencies pump out
1
Form SW401-Wet Detention Basin-Rev.4
G1
Parts I. & II. Design Summary, Page 2 of 2
WATER QUALITY POND CALCULATIONS
Drainage area: DA-2A
Project Name
Spring Hill Subdivision
Project Number
DWQ Project# 06-1052, Ver. 2
Date
09-Oct-08
3rd revision
2nd revision
1st revision
1 Wr f
Water Quality Pond Drainage Area Data
Project Spring Hill Subdivision
Project No. DWQ Project# 06-1052, Ver. 2
Date 9-Oct-08
Total site area 2,082,714 square feet = 47.81 acres
Draina a area to and Other Drainage Area

Impervious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site buildings 0 285,000 285,000 0 0
On-site streets 0 188,269 188,269 0 0
On-site parking 0 0 0 0 0
On-site sidewalks 0 24,642 24,642 0 0
Other on-site 0 0 0 0 0
Total off-site impervious- 0 0 0 0 0
Total Impervious 0 497,911 497,911 0 0
Draina a area to and Other Drainage Area

Non-impervious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site grass/landscape 0 916,353 916,353 0 0
On-site woods 2,082,714 668,450 -1,414,264 0 0
Other undeveloped 0 0 0 0 0
Total off-site non-impervious 0 0 0 0 0
Total non-impervious 2,082,714 1,584,803 -497,911 0 0
Total Drainage Area 2,082,714 2,082,714 0 0 0
Percent impervious 0.0 23.9 219 n/a n/a
Notes:
Since the overall Proposed Percent Impervious area is below 24% no BMP devise was required and
no futher calculations were required.
DA-2A.xls
Site Drainage Area Data Page 1 of 1 Printed 10/29/2008 3:58 PM
!3
WATER QUALITY POND CALCULATIONS
Drainage area: DA-2B
Project Name
Spring Hill Subdivision
Project Number
DWQ Project# 06-1052, Ver. 2
Date
09-Oct-08
3rd revision
2nd revision
1st revision
(12)
' Water Quality Pond Drainage Area Data
' Project Spring Hill Subdivision
Project No. DWQ Project# 06-1052, Ver. 2
' Date 9-Oct-08
Total site area 302,174 square feet = 6.94 acres
Draina a area to and Other Drainage Area

Impervious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site buildings 0 57,500 57,500 0 0
On-site streets 0 50,319 50,319 0 0
On-site parking 0 0 0 0 0
On-site sidewalks 0 6,400 6,400 0 0
Other on-site 0 0 0 0 0
Total off-site impervious 0 0 0 0 0
Total Impervious 0 114,219 114,219 0 0
Draina a area to and Other Drai nage Area

Non-impervious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site grass/landscape 0 151,208 151,208 0 0
On-site woods 302,174 36,747 -265,427 0 0
Other undeveloped 0 0 0 0 0
Total off-site non-impervious 0 0 0 0 0
Total non-impervious 259,883 187,955 -71,928 0 0
Total Drainage Area 259,883 302,174 42,291 0 0
Percent impervious 0.0 37.8 37.8 n/a n/a
' Notes:
Since the overall Proposed Percent Impervious area is above 24%, design calations are included for
the BMP device.
DA-2B.xls
Site Drainage Area Data
Page 1 of 1
0S
Printed 10/29/2008 3:34 PM

' Water Quality Pond Surface Area Calculations for Wet Ponds
Project S ri,'g H i Su di s ?
' Project No. D P1 o ect 06-1052", Ver-
' Date ..0cf-08
' Total on-site drainage area to pond 302,174 square feet
Total impervious area in drainage area 114,219 square feet
' Average water depth of basin at normal pool 7.5 feet

Location of site Lillington, NC
Site region Piedmont
% Impervious cover 37.8 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 0.0 percent
' For a site in a Coastal County w/out Vegetative Filter 0.0 percent

' Required surface area of pond:
For a site in the Piedmont
4,01500
square feet
For a-site-in a-Coastal County w/ Vegetative Filter _ 0.0 square feet
For a site in a Coastal County w/out Vegetative Filter 0,0 square feet

Notes:

'
DA-26.xls
Pond SA -Wet Pond Page 1 of 1 Printed 10/29/2008 3:34 PM

Water Quality Pond Stormwater Runoff Volume Calculations
Project Spring Hill Subdivision
Project No. DWQ Project# 06-1052, Ver. 2
Date 9-Oct-08

Drainage area 302,174 square feet
Impervious area 114,219 square feet
Rainfall depth 1.00 inches

Percent Impervious 37.8 percent

R(v)=0.05+0.009*(Percent impervious)
Runoff coefficient - R(v) 0.39 in/in
Runoff volume=(Design rainfall)*(R(v))*(Drainage area)
Runoff volume 9,825.5 cubic feet
Notes:
DA-2B As
Runoff Volume Calcs Page 1 of 1
Printed 10/29/2008 3:34 PM
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8D
Water Quality Basin Dewatering Time Calculations
Project Spring Hill Subdivision
Project No. DWQ Prc3e-?t# 06-1052, V r. 2
Date 09-Oct-08
Surface area of basin 8,733 square feet
Maximum head of water above dewatering hole 2.00 feet
Orifice coefficient 0.60
Diameter of each hole 1.50 inches
Number of holes 1
Cross sectional area of each hole = 0.012 square feet
Cross sectional area of each hole = 1.8 square inches

Cross sectional area of dewatering hole(s) = 0.012 square feet
Cross sectional area of dewatering hole(s) = 1.8 square inches

Dewatering time for basin = 116.1 hours
Dewatering time for basin = 4.8 days
Calculations based on NC Sediment and Erosion Control Manual
Page 8.07.8
Notes:
19

1 Water Quality Pond Summary Information
Project S in g KHaub Subdivision .
1 Project No. D WQ Pr o;ec";t 06-1052, Ver. 2
1 Date 9- C t-08
Drainage area to pond 302,174 square feet = 3.94 acres
1 Impervious area in drainage area 114,219 square feet = 2,62 acres
Bottom of pond elevation 226.00 feet
1 Normal pool elevation 232.50 feet
Pond volume at normal pool 13,613 cubic feet
' Required volume for design rainfall 9,325 cubic feet
Required surface area for pond 4,050 square feet
1 Volume provided for storage of design rainfall = 14,956 cubic feet at elevation 234.5
Surface area provided at normal pool 5,408 square feet
1
1
1
1
1
DA-2B.xls
Summary Data Page 1 of 1 Printed 10/29/2008 3:35 PM
1 Zo
-- -- =hermit No.
~ r (to be provided by D WQ)
?jj? of `NATE9
NCDENR: ,? -
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
' WET DETENTION BASIN SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Part 111) must be printed, filled out and submitted along with all of the required information.
11. PROJECT INFORMATION
Project name spring Hill Subdivision
Contact person Thomas J Spaulding
Phone number 919-854-7990 -
Date 10/9/2008
Drainage area number DA -213

II. DESIGN INFORMATION
Site Characteristics
Drainage area 302,174.00 ft
' Impervious area 114,219.00 ft2
% impervious 37.80 %
Design rainfall depth 1.00 in
Storage Volume: Non-SR Waters
Minimum volume required 9,925.00 ft3
Volume provided 14,956.00 ft3
' Storage Volume: SR Waters
1-yr, 24-hr runoff depth in
Pre-development 1-yr, 24-hr runoff ft3
Post-development 1-yr, 24-hr runoff ft3
' Minimum volume required ft3
Volume provided ft3
Peak Flow Calculations
' 1-yr, 24-hr rainfall depth 2-88 in
Rational C, pre-development - -- 0.20 - (unitless) - -- -
Rational C, post-development 0.50 (unitless)
Rainfall intensity.1-yr, 24-hr storm 4.87 in/hr
' Pre-development 1-yr, 24-hr peak flow 6.76 ft3/sec
Post-development 1-yr, 24-hr peak flow 16.90 ft3lsec
Pre/Post 1-yr, 24-hr peak flow control 10.14 ft'/sec
' Basin Elevations -
Basin bottom elevation 226.00 ft
Sediment cleanout elevation 227.00 ft
Bottom of shelf elevation 232.00 ft
Permanent pool elevation 232.50 ft
SHWT elevation ft
' Top of shelf elevation
Temporary pool elevation 233.00
234
50 ft
ft
.

1

Form SW401-Wet Detention Basin-Rev.4
2?
Parts 1. & H. Design Summary, Page 1 of 2
' .? ?? -- alb -- -? ?• Pennit-I(to be provided by DWQ)
II. DESIGN INFORMATION
Volume and Surface Area Calculations
' SA/DA ratio 1.34 (unitless)
Surface area at the bottom of shelf 3,948.00 ftz
Volume at the bottom of shelf 11,274.00 ft3
Permanent pool, surface area required 4,050.00 ft2
Permanent pool, surface area provided 5,408.00 ft2 OK
Permanent pool volume 17, 213.00 ft3
Average depth for SA/DA tables 3.18 ft OK
' Surface area at the top of shelf 7,068.00 ftz
Volume at the top of shelf 16,732.00 ft3
Forebay volume 3,600.00 ff3
Forebay % of permanent pool volume 20.91 % ,K
' Temporary pool, surface area provided 8,733.00 ftz
Drawdown Calculations
' Treatment volume drawdown time
Treatment volume discharge rate 4.80
0.05 days
ft3/s K
Pre-development 1-yr, 24-hr discharge 0.05 ft3ls OK
Post-development 1-yr, 24-hr discharge _ 0.05 ft3/s OK
' Additional Information
Diameter of orifice 1.5 in
Design TSS removal 85 %
Basin side slopes 3.00 :1 OK
' Vegetated shelf slope 10.00 A OK
Vegetated shelf width 10.00 ft :3K
Length of flowpath to width ratio 5.00 :1 OK
Length to width ratio 2.00
:1
OK
Trash rack for overflow & orifice? Y (Y or N) OK
Freeboard provided 1.00 ft OK
Vegetated filter provided? Y (Y or N) OK
' Recorded drainage easement provided? Y (Y or N) OK
Capures all runoff at ultimate build-out? Y (Y or N) OK
Drain mechanism for maintenance or emergencies pump out

1
1
Form SW401-Wet Detention Basin-Rev.4 Parts I. & II. Design Summary, Page 2 of 2
1
1
1
1
WATER QUALITY POND CALCULATIONS
Drainage area: DA-3
Project Name
Spring Hill Subdivision
Project Number
DWQ Project# 06-1052, Ver. 2
Date
09-Oct-08
3rd revision
2nd revision
1 st revision
0
Water Quality Pond Drainage Area Data
' Project Spring Hill Subdivision
Project No. DWQ Project# 06-1052, Ver. 2
' Date 9-Oct-08
Total site area 2,080,767 square feet = 47.77 acres
i
Draina a area to and Other Drai nage Area

Impervious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site buildings 0 297,500 297,500 0 0
On-site streets 0 178,256 178,256 0 0
On-site parking 0 0 0 0 0
On-site sidewalks 0 22,145 22,145 0 0
Other on-site 0 0 0 0 0
Total off-site impervious- 0 0 0 0 0
Total Impervious 0 497 901 497,901 0 0
Draina a area to and Other Drai nage Area

Non-impervious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site grass/landscape 0 968,602 968,602 0 0
On-site woods 2,080,767 614,264 -1,466,503 0 0
Other undeveloped 0 0 0 0 0
Total off-site non-impervious 0 0 0 0 0
Total non-impervious 2,080,767 1,582,866 -497,901 0 0
Total Drainage Area 2,080,767 2,080,767 0 0 0
Percent m pervious 0.0 23.9 23.9 n/a n!a
Notes:
Since the! overall Proposed Percent Impervious area is below 24% no BMP devise was required and
no futher calculations were required.
DA-3.xls
Site Drainage Area Data Page 1 of 1 Printed 10/29/2008 3:58 PM
I (i4-1)
WATER QUALITY POND CALCULATIONS
' Drainage area: DA-4
Project Name
' Spring Hill Subdivision
Project Number
DWQ Project# 06-1052, Ver. 2
1
t
Date
09-Oct-08
3rd revision
2nd revision
1 st revision
2s
Water Quality Pond Drainage Area Data
Project Spring Hill Subdivision
Project No. DWQ Project# 06-1052, Ver. 2
Date 9-Oct-08
Total site area 187,786 square feet = 4.31 acres
Draina a area to and Other Drai nage Area

Impervious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site buildings 0 15,000 15,000 0 0
On-site streets 0 17,492 17,492 0 0
On-site arkin 0 0 0 0 0
On-site sidewalks 0 2,528 2,528 0 0
Other on-site 0 0 0 0 0
Total off-site impervious 0 0 0 0 0
Total Im pervious 0 35,020 35,020 0 0
Draina a area to and Other Drai nage Area

Non-imp.-rvious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site rass/landsca e 0 46,664 46,664 0 0
On-sitev?roods 187,786 106,102 -81,684 0 0
Other undeveloped 0 0 0 0 0
Total off-:site non-impervious 0 0 0 0 0
Total non-impervious 187,786 152,766 -35,020 0 0
Total Drainage Area 187,786 187,786 0 0 0
Percent ,n pervious 0.0 18.6 18.6 n/a n/a
Notes:
Since the overall Proposed Percent Impervious area is below 24% no BMP devise was required and
no futher calculations were required.
DA-4.xls
Site Drainage Area Data Page 1 of 1
CZ-0
Printed 10/29/2008 3:58 PM
r?
WATER QUALITY POND CALCULATIONS
Drainage area: DA-5
Project Name
Spring Hill Subdivision
Project Number
DWQ Project# 06-1052, Ver. 2
Date
09-Oct-08
3rd revision
2nd revision
1 st revision

27
Water Quality Pond Drainage Area Data
Project
Project No.
' Date
Total site area
i
Spring Hill Subdivision
DWQ Project# 06-1052, Ver. 2
9-Oct-08
43,733 square feet = 1.00 acres
Draina a area to and Other Drai nage Area

Impervious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site buildings 0 7,840 7,840 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 0 0 0 0
Total off-site impervious 0 0 0 0 0
Total Im >ervious 0 7,840 7,840 0 0
Draina a area to and Other Drai nage Area

Non-imp E;rvious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site rass/landsca e 0 28,353 28,353 0 0
On-site woods 43,733 7,540 -36,193 0 0
Other undeveloped 0 0 0 0 0
Total off-site non-impervious 0 0 0 0 0
Total non-impervious 43,733 35,893 -7,840 0 0

Since the overall Proposed Percent Impervious area is below 24% no BMP devise was required and
no futher calculations were required.
r
DA-5.xls
Site Drainage Area Data Page 1 of 1 Printed 10/29/2008 3:59 PM
T
otalDraina a Area 43,733 43,733 0 0 0

Percent Im ervious
0.0
17.9
17.9
n/a
n/a
Notes:
1
1
1
1
1
1
1
1
1
1
1
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1
WATER QUALITY POND CALCULATIONS
Drainage area: DA-6
Project Name
Spring Hill Subdivision
Project Number
DWQ Project# 06-1052, Ver. 2
Date
09-Oct-08
3rd revision
2nd revision
1st revision
Z9)
Water Quality Pond Drainage Area Data
Project Spring Hill Subdivision
Project No. DWQ Project# 06-1052, Ver. 2
Date 9-Oct-08
Total site area 191,300 square feet = 4.39 acres
Dra ina a area to and Other Drainage Area

Im ervious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site buildings 0 30,000 30,000 0 0
On-site streets 0 13,713 13,713 0 0
On-site rarkin 0 0 0 0 0
On-site sidewalks 0 2,014 2,014 0 0
Other on-site 0 0 0 0 0
Total off-site impervious 0 0 0 0 0
Total Im )ervious 0 45,727 45,727 0 0
Draina a area to and Other Draina a Area

Non-imp.rvious areas Existing
s Proposed
s Change
s Existing
s Proposed
s
On-site rass/landsca e 0 94,743 94,743 0 0
On-site woods 191,300 50,830 -140,470 0 0
Other undeveloped 0 0 0 0 0
Total off-site non-impervious 0 0 0 0 0
Total non-impervious 191,300 145,573 -45,727 0 0
Total Draina a Area 191,300 191,300 0 0 0
Percent Impervious 0.0 23.9 23.9 n/a n/a
Notes:
Since the overall Proposed Percent Impervious area is below 24% no BMP devise was required and
no futher calculations were required.
DA-6. xls
Site Drainage Area Data
Page 1 of 1
30
Printed 10/29/2008 3:59 PM