SW8980728_COMPLIANCE_19990216

i
STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
I SW
DOC TYPE
I ❑ CURRENT PERMIT
❑ APPROVED PLANS
❑ HISTORICAL FILE
COMPLIANCE EVALUATION INSPECTION
DOC DATE
I /�`,✓�/(p
YYYYMMDD

f
2/12199
CDC
COLLEGE ROAD TRACT
Stormwater Calculations
97074
Total Drainage Area
s , ft.
acres
121,000
2.78
impervious Area
Land Use I
sq. ft,
acres
fast food bldg 1
3,700
0.08
fast food asphalt 1
30,500
0.70
fast food concrete 1
2.956
0.07
service station bldg 1
2.700
0.06
service station canopy 1
5,320
0.12
service station asphalt 1
28,840
0.66
service station concrete 1
400
0.01
future area 1
6.075
0.14
[Total 1
60,491
1.85
Stormwater Calculations:
Time of Concentration:
Hydraulic Length (L) = 500 ft.
change in Height(H) = 1 �5 ft.
Tc = (L' 1H)' s 1 128
8.76 min.
Flow for 10 year, 6 hour Storm (010):
QPRE _ (CPRE) X (110) x (Area)
5.02 cfs
QPosT = (CPosr) x (110) x (Area)
14.46 cfs `
1
ooe orora o taparrry ror i u year aawm.
CN = (98)(°% imp.) + (60)(1-IN imp.)
86
P = 4.80 in. for 10 yr, 6 hr storm
S = 10001CN - 10
1.63
Depth (D)= [P-(0.2)(S)]2 1 ]P+(0.8)(S}]
3.28
Time to Peak
Detention Pond Design:
Pond Size:
Elevation
ft.
Surface Area
(sq. ft.
Normal Pool
27.50
6.343
Flood Pool
29.00
8.161
Top of Bank
30.50
10,141
Bottom of Pool
21.00
0
Total Provided Storage Volume: 1
Vol. _ ((Normal pool $A + Flood EPool SA) 1 21
x (Flood Pool elov. - N.P, elev,)
10.878 cu.ft. i
97074POND.xls
°% impervious = 0.665
= 66.5%
use 68.0%
CPRE = 0.25
CPosT = (°% imp.)(.95)+(1-O% imp.)(.25)
= 0.72
0 = 7.23 inlhr
I50 8.87 in/hr
Flow for 50 year, 6 hour Storm (Q50):
QPRE _ (CPRF) x (150) x (Area)
6.16 cfs
QPos-r = (CPosT) x (190) x (Area)
17.74 cfs
Soil Storage Ca aci for 50 year Storm:
CN = (98)(°% imp.) + (60)(1-0% imp.)
86
P = 6.42 in. for 50 yr, 6 hr storm
S= 10001CN-10
Depth (D)= [P-(0.2)(S)f/ [P+(0,8)(S)]
= 4.61 in.
Time to Peak Flaw:
TP = ((43.5)(0)(Area)] 1 050,PosT
32.76 min.
State Surface Area Requirement at normal ool:
Pond side slopes = 3 :1
Depth
1 of 2
Z.locr
below N.P. = 6.5 ft.
SAIDA = 0.0320
(Chart for 90°% T55 Removal for Wet Detention
Pond without Vegetative Filter
Required SA = (SA1DA) x (Total Drainage Area)
= 3,872 s , ft,
State Volume Requirement for first 1" of runoff:
Vol. = [(1112) x (DA) x (°% imp.)] +
[(1112) x (DA) x (1-0% imp.) x C]
C = 0.2
= 7,383 cu.ft.
STORMWATER
D E C E I V E
FEB 16 1999
PROJ ff w ob_�28
1 of 2
Z.locr
below N.P. = 6.5 ft.
SAIDA = 0.0320
(Chart for 90°% T55 Removal for Wet Detention
Pond without Vegetative Filter
Required SA = (SA1DA) x (Total Drainage Area)
= 3,872 s , ft,
State Volume Requirement for first 1" of runoff:
Vol. = [(1112) x (DA) x (°% imp.)] +
[(1112) x (DA) x (1-0% imp.) x C]
C = 0.2
= 7,383 cu.ft.
STORMWATER
D E C E I V E
FEB 16 1999
PROJ ff w ob_�28

2J 12199 COLLEGE ROAD TRACT 97074
CDC ` Stormwater Calculations
ore6a
Required Volume Provided Volume
Vol. = 20% of storage volume Normal Pool SA = 2,567 sq. ft.
4,123 cu. ft. Bottom SA = 745 s . ft.
Vol. _ [(N.P. SA+ F.P. SA) / 2] x (F.P. el. - N.P. el.)
= 4,140 cu. ft,
depth = 2.5 ft.
Outlet Structure Design:
Flow for 2-day drawdown: Flow for 5-day drawdown:
for 1st V of stormwater, i for 1 st 1" of stormwater,
Q = Provided Vol. 1 172,800 sec. (2-days) 0 = Provided Vol. / 432,000 sec. (5-days)
= 0.063 cfs — 0.025 cfs
Ke utrea Area or m a ror z-oay arawaown:
A= Q 1(Cd x SQRT(2 x g x h))
Cd = 0.6
9 = 32.2 ft•Isz
h = (F.P. elev.- N.P. elev.)12
7= 0,75 ft.�
A = 0.0151 sq. ft.
I
Diameter of Pipe for 2-day drawdown:
DIA. = SQRT[(A x 4)1 pi]
0.1: ft. jl
i:66 in.
Outlet Structure Check:
Using a 4' x 4' Basin,
Perimeter W = 16 ft.
Q = CIA 1
C = (% imp.)(95) + (1-% imp.)(25)
= 0.72
1 = 7.23 in, for a 10 yr. Storm
A = 2.78 Acres
= 14.46 cfs
I
0= CwxLxH"5 4
H = [Q I (Cw x L)]�"j
Cw = 3 li
0.45 ft.
I
Peak elevation = flood pool elevation + H
29.45 ft.
me urrea ,urea or fl a ror z)-aay orawoown:
A= Q! [Cd x SQRT(2 x g x h))
Cd = 0.6
9 = 32.2 ft.lsZ
h = (F.P. elev. - N.P. elev.)12
= 0,75 ft.
A = 0.0060 sq.ft.
Diameter of Pipe for 5-day drawdown:
DIA. = SQRT((A x 4) 1 pi]
0.0877 ft.
— 1.05 in.
97074POND.xis 1 2 of 2

A. Site Plan
✓ i.
2.
3.
4.
5.
7.
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24.
STORMWATER SUBMITTAL REQUIREMENTS
DETENTION POND
De velopment/Project Name
Engineer name and firm.
Legend
North Arrow
Location Map with direction, distance to named streets, NCSR numbers.
Scale
Date
Revision number and date.
Original contours, proposed contours, spot elevations, finished floor elevations.
Existing drainage, including off -site. Map of offsite area?
Property/Project boundary lines, dimensioned.
Mean High Water Line, if necessary.
Drainag Basemen pipe sizes. 6�'Pcy7cj
Wetlands delineated, or a note on the plans that none exist.
Details of the road, parking, cul-de-sacs, including sidewalks, curb and gutter..
Drainage area to each pond delineated.
Dimensions of the permanent pool. — FUreb�j r�c�i,ar
Vegetated filter detail if using 85 % TSS. This is NOT a connector ditch.
Dimensions of the roa ,par 'n cul-de-sacs, sidewalks, and curb and gutter.
Unit of otprint with dimensions and concrete wood deck areas noted.for apartments
or condo development.
Forebay at each inlet. Prefer one inlet
Inlets located such that entire pond is used for treatment and no short-circuiting.
section with:
Bottom elevation
Permanent pool elevation PP
Storage pool elevation SP
Slopes: 3:1 above permancnt pool
Vegetated shelf @6:1 slope, with begin and end elevations around pond.
Forebay bottom elevation, 3:1 slopes,
Forebay weir elevation between PP and SP.
t structure detail with trash rack and orifice.
25. Note c
26. A 3:1y
n plans that all roof drains must be directed so as to be picked up by the pond.
L: W ratio has been provided for the pond.

STORMWATER SUBMITTAL REQUIREMENTS.
DETENTION POND (cont)
B.
Calculations
✓
1.
85 % or 90 % TSS Chart noted.
2.
Pond depth.
3.
SA/DA ratio calculation.
4.
Required surface area at permanent pool.
_
5.
Provided surface area at permanent pool (Based on pond dimensions)
6.
Required volume.
7.
Provided volume.
t i
8.
Orifice size based on provided volume.
9.
Engineer seal.
ijiA_
10.
Built -upon area to each pond.
t
11.
Forebay designed to hold 20% of the first inch.
12.
Non -erosive flow in the vegetated filter, if using 85 % TSS.
C.
Supporting Documentation
1. Completed permit application
.i a. Is the person who signed the landowner or a leasee? Must be landowner.
v b. All sections completely filled in.
C. Check signature per .1003 (e). Make sure title is provided.
d. If agent signs, signatory authorization from owner.
e. Wet detention supplement sheet provided.
f. Mailing address & phone of applicant- no C/O.
g. Verify water body classification.
h. Missing information:.L/12
vl� 2. Signed Operation and Maintenance Plan (includes all items on DWQ 0 & M form.)