HomeMy WebLinkAboutPSI Corporate Office - Stormwater Runoff Management and Treatment CalculationsPSI CORPORATE OFFICE
STORMWATER RUNOFF
MANAGEMENT AND TREATMENT
CALCULATIONS
Address:
2204 East Lanark Street
Meridian, Idaho 83642
PREPARED BY:
Breckon Land Design, Inc.
P.O. Box 44465
Boise, Idaho 83711
ph: (208) 376-5153
fax: (208) 376-6528
OF
C
U
1 536
�Sl
Project No. 13016.01
June 18, 2013
PURPOSE
The purpose of this report is to confirm that the
for the PSI Corporate Office is adequate for the
of Environmental Quality standards.
on-site storm water management system design
100 year design storm per the Idaho Department
SITE DESCRIPTION
The proposed site is located at 2204 East Lanark Street, Meridian, Idaho 83642.
The limits of construction are approximately 2.00 acres as shown on the attached site plan.
Currently the site is a relatively flat with existing improvements. Runoff water from the site is
conveyed to valley gutters and curb gutters that flow water to an underground drainage system.
The post development runoff will divide runoff between new grass infiltration swales and a new
underground seepage bed. The site is bordered by commercial development on the north,
south, west, and east. Dewatering is not expected.
DESIGN CRITERIA
The system is designed to accommodate the 100 year design storm using infiltration basin
(swale) designs in accordance with recommendations given by the IDEQ Storm Water Best
Management Practices Catalog.
The storm water runoff flows were calculated using the Rational Method with a weighted post
development runoff coefficient calculated for each drainage area. The rainfall intensity used was
taken from the Intensity -Duration -Frequency Curve for Zone A in the IDEQ Storm Water Best
Management Practices Catalog for the 100 year design storm. See Appendix B for a copy of this
curve.
PEAK FLOW ANALYSIS OUTLINE
The proposed storm drainage piping system is sized to provide the necessary capacity to
convey the 100 -year storm event and to provide for initial settlement of sediments in the runoff.
The following steps were taken to design the storm drain lines.
1. Calculate the individual drainage basin areas (A) and estimate the Runoff Coefficient
(C) and Time of Concentration (T) values for the developed basins.
2. Determine the maximum flow for each basin using the Rational Equation (Q=CIA),
determining the Rainfall Intensity (1) from the Zone A Intensity -Duration -Frequency
curves from the estimated T values.
3. Size the storm drain lines, sand and grease traps and inlets to accommodate the peak
flows.
PEAK FLOW ANALYSIS RESULTS
The storm system has been sized to accommodate the 100 -year peak flow rates. Appropriately
sized infiltration trenches have been located to provide initial settlement of sediments in the runoff
and to accommodated storm water on site.
DESIGN STORM DETENTION ANALYSIS OUTLINE
The proposed storm drainage detention system is sized to provide the necessary capacity to
store the 100 -year storm event and to provide for initial settlement of sediments in the runoff.
The following steps were taken to design the storm drain retention.
1. Calculate the individual drainage basin areas (A) and estimate the Runoff Coefficient (C)
and Time of Concentration (T) values for the developed basins.
2. Determine the maximum flow for each basin using the Rational Equation (Q=CIA),
determining the Rainfall Intensity (1) from the Zone A Intensity -Duration -Frequency curves
from the estimated T values.
3. Size the swale area and seepage bed size to accommodate the required volume.
100 YEAR DETENTION RESULTS
The proposed detention basin system and underground seepage bed has been designed to
adequately detain the 100 -year design storm event.
2
Appendix A
Drainage Basin Map: N.T.S.
1233.19'
DRAINAGE AREA #3
TOTAL SO: 41,014.26 sq.ft.
TOTAL AC: 0.94
Impervious: 13,625.69 sq.ft.
Ac: 0.31
Pervious: 27,388.57 sq.ft.
Ac: 0.63
■■■
DRAINAGE
AREA #2
TOTAL SO:
7,846.88sg.ft.
TOTAL AC:
0.18 6
Impervious:
3,627.13 sq.ft.
Ac: 0.084
Pervious: 4,219.75 sq.ft.
Ac: 0.096
DRAINAGE AREA #1
TOTAL SO: 28,895.25 sq.ft.
TOTAL AC: 0.663
Impervious: 18,152.49 sq.ft.
Ac: 0.42
Pervious: 10,742.76 sq.f�
Ac: 0.24
PSI CORPORAT
OFFICE
FINISH FLOOR
--------------------------------------
p5c�� IANARK S�RtET
T DRAINAGE BASIN MAP
N 5GALE: I"= 60'-0"
Appendix B
Intensity -Duration -Frequency Curve
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w
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z
1.0
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as
0.4
Lo
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}- 02
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J
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Q D4
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10 15 20 30 40 5060 2 3 4 5 6 5 10 12 is z4
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Appendix C
Runoff Coefficients
Table C-1. Typical "C" Values
Description of Area
Runoff Coefficients
Business
Downtown Areas
0,70-0.95
Neighborhood Areas
0.50- 0.70
Residential
Single-family areas
0.30-0.50
Multi -units, detached
0.40-0.60
Multi units, attached
0.60-0.75
Residential (suburban)
0.25-0.40
Apartment dwelling areas
0,50 - 0.70
Industrial
Light Areas
0.50-0.80
Heavy Areas
0.60-0.90
Parks, cemeteries
0.10-0.25
Playgrounds
0.20-0.35
Railroad yard areas
0.20-0.40
Unimproved areas
0.10-0.30
Streets
Asphalt
0.70-0.95
Concrete
0.80-0.95
Brick
0.70-0,85
Drives and Walks
0.75-0.85
Roofs
0.75-0.95
Lawns - course textured soil (greater than 85% sand)
Slope: Flat, 2%
0,05-0.10
Average, 2-7%
0.10-0.15
Steep, 7%
0.15-0.20
Lawns - tine textured soil (greater than 40% clay)
Slope: Flat, 2%
0.13-0.17
Average, 2-7%
0.18-0.22
Steep, 7%
0.25-0.35
44 Developing Your Stormwater Pollution Prevention Plan A Guide for Construction Sites
Appendix D
Storm Water Calculations
PSI Corporate Office, Meridian, Idaho
DRAINAGE AREA #1
Area = 28,895 sf
Area = 0.66 acres
C = 0.67
Infiltration Characteristics (floor only):
Infiltration Rate =
2 in per hr
Width =
95 ft
Length -
100 ft
A perc. =
1500 sf
Q perc. -
250.00 cf per hr
Q perc. -
0.0694 cfs
Infiltration Characteristics
1213 sidewalls only):
Infiltration Rate =
2 in per hr
Width (2x)
30 ft
Length 2x -
200 ft
A perc. =
468.07 sf
Q perc. -
78.01 cf per hr
Q perc. -
0.0217 cfs
STORAGE VOLUME
Time Time
min. sec.
REQUIRED (100 Year Storm):
Intensity Q dev.
inches/hr) (cfs)
Vin
(cf
V out
cf
V storage
51
300
4.41
1.96
588
21
567
10
600
3.2
1.42
855
42
813
15
900
2.5
1.11
1,002
63
939
20
1200
2.2
0.98
1,175
83
1,092
30
1800
1.6
0.71
1,282
125
1,157
40
2400
1.4
0.62
1,496
167
1,329
50
3000
1.2
0.53
1,603
208
1,394
60
3600
1.1
0.49
1,763
250
1,513
120
7200
0.6
0.27
1,923
500
1,423
180
10800
0.45
0.20
2,164
750
1,414
240
14400
0.35
0.16
2,244
1,000
1,244
300
18000
0.3
0.13
2,404
1,250
1,154
360
21600
0.26
0.12
2,500
1,500
1,000
480
28800
0.22
0.10
2,821
2,000
821
600
36000
0.18
0.08
2,885
2,500
385
720
43200
0.14
0.06
2,693
3,000
-307
1080
64800
0.12
0.05
3,462
4,500
-1,038
1440
86400
0.085
0.04
3,270
6,000
-2,730
Vs Max= 1,513 of Maximum Storage Required
Seepage Bed Volume (38% Voids)
Seepage Bed Volume (x 15%)
1 hour
2 hours
3 hours
4 hours
5 hours
6 hours
8 hours
10 hours
12 hours
18 hours
24 hours
Vs Max =
1,513 cf
Maximum Storage Required
1000 al & 1 1500 al Sand and Grease Trapb Amcor Pre Cast
A b =
V sw =
3,026 sf
of 6" deep Swale required
1,008.7
sf
V sw =
2,017 sf
of 9" deep swale required
756.5
sf
V sw =
1,513 sf
of 12" deep swale required
504.3
sf
Depth =
1.0087 ft
Swale Size=
15
ft wide x 100 ft long x
1.01
ft dee
Velocity Through
Baffle:
T e:1
1000 al & 1 1500 al Sand and Grease Trapb Amcor Pre Cast
A b =
4 sf See appendix D
Q 10 min. I
1.42 cfs 1100 year Peak Q dev. At 10 min duration
Velocity = 1
0.36 ft per sec.
See a e Bed Recove Time (floor):
Vs=
1,513cf
er
Q pc =
250.00 cf per hr
Time Rec =
6.11 hours
seeoacle Bed Recove Time 213 sidewalls :
Vs=
1,513 of
Qerc =
78.01 cf per hr
Time Rec =
19.4 hours
Time Rec = 1
0.81 Jdays
Wei hted Runoff Coefficient "C"
Runoff coefficients= 0.95 paved (impervious)
0.2 landscape (pervious)
Impervious area = 18,152.49 sf 17244.866 sf
Pervious area I 10,742.76 sf I 2148.552 sf
Total Area = 128,895.25 1 sf I 0.67 "C'
of 18" deep swale required.
of 24" deep swale required
of 36" deep swale required
Psi corporate Office, Meridian, Idaho
i
DRAINAGE AREA #2
Area = 7,847 sf
Area = 0.18 acres
C = 0.55
Infiltration Characteristics (floor only):
Infiltration Rate =
2 in per hr
Width =
10 ft
Length =
60 ft
A perc. =
600 sf
Q perc. =
100.00 cf per hr
Q perc. -
0.0278 cfs
Infiltration Characteristics
( 2/3 sidewalls only):
Infiltration Rate -
2 in per hr
Width (2x) -
20 ft
Length 2x -
120 ft
A perc. =
136.51 sf
Q perc. =
22.75 cf per hr
1
0.0063 cfs
STORAGE VOLUME
Time Time
(min.) sec.
REQUIRED (100 Year Storm):
Intensity Q dev.
(inches/hr) (cfs
Vin
cf)
V out
(cf)
V storage
(c
5
300
4.41
0.43
130
8
122
10
600
3.2
0.32
189
17
172
15
900
2.5
0.25
222
25
197
20
1200
2.2
0.22
260
33
227
30
1800
1.6
0.16
284
50
234
40
2400
1.4
0.14
331
67
264
50
3000
1.2
0.12
355
83
271
60
3600
1.1
0.11
390
100
290
120
7200
0.6
0.06
425
200
225
180
10800
0.451
0.04
479
300
179
240
14400
0.351
0.03
496
400
96
300
18000
0.3
0.03
532
500
32
360
21600
0.26
0.03
553
600
-47
480
28800
0.22
0.02
624
800
-176
600
36000
0.18
0.02
638
1,000
-362
720
43200
0.14
0.01
596
1,200
-604
1080
64800
0.12
0.01
766
1,800
-1,034
1440
86400
0.085
0.01
723
2,400
-1,677
Vs Max - 290 cf Maximum Storage Required
Seepage Bed Volume (38% Voids)
Seepage Bed Volume (x 15%)
1 hour
2 hours
3 hours
4 hours
5 hours
6 hours
8 hours
10 hours
12 hours
18 hours
24 hours
Vs Max =
290 cf
Maximum Storage Required
(1) 1000 al &1) 1500 al Sand and Grease Trap by Amcor Pre Cast
A b =
4;T See appendix D
V sw =
580 sf
of 6" deep swells, required
193.3
sf
of 18" deep swale required
V sw =
387 sf
of 9" deep swale required
145.0
sf
of 24" deep swale required
V sw =
290 sf
of 12" deep swale required
96.7
sf
of 36" deep Swale required
Depth =
0.4833 ft
Swale Size=
10
ft wide x 60 ft long x
0.48
ft deep
Velocity
Through Baffle:
Type:
(1) 1000 al &1) 1500 al Sand and Grease Trap by Amcor Pre Cast
A b =
4;T See appendix D
Q 10 min.
0.32 cfs 1100 year Peak Q dev. At 10 min duration
Velocity
= I 0.08 ft per sec.
Seepage Bed Rec very Time Floor:
V s = 290 cf
Q perc = 100.00 cf er hr
Time Rec = 2.9 hours
Seepage Bed Recove Time 2/3 sidewalls :
V s =
290 1cf
Q perc =
22. 75 cf per hr
Time Rec =
12.7hours
Time Rec =
0.53 days
0.2 landscape (pervious)
Impervious area = 3,627.13 sf 3445.7735 sf
Pervious area I 4,219.75 sf 843.95 sf
Total Area = I 7,846.88 sf 0.55 "C"
PSI Corporate Office, Meridian, Idaho
DRAINAGE AREA #3
Area= 41,014 sf
Area = 0.94 acres
�j
C = 0.52
Infiltration Characteristics (floor only):
Infiltration Rate =
2 in per hr
Width =
15 ft
Length =
55 ft
A perc. =
825 sf
Q perc. =
137.50 cf per hr
Q perc. =
0.0382 cfs
Infiltration Characteristics
1 213 sidewalls only):
Infiltration Rate =
2 in per hr
Width 2x =
30 ft
Length (2x) =
110 ft
A perc. =
677.20 sf
Q perc. =
1 12.87cf per hr
Q perc. =
0.0314 cfs
STORAGE VOLUME REQUIRED (100 Year Storm):
Time Time Intensity Q dev.
min. (sec.) (inches/hr) (cls)
Vin
(cf)
V out
(CO(CO
V storage
51
300
4.41
2.14
641
11
630
10
600
3.2
1.55
933
23
910
15
900
2.5
1.21
1,093
34
1,059
20
1200
2.2
1.07
1,282
46
1,237
30
1800
1.6
0.78
1,399
69
1,330
40
2400
1.4
0.68
1,632
92
1,541
50
3000
1.2
0.58
1,749
115
1,634
60
3600
1.1
0.53
1,924
138
1,786
120
7200
0.6
0.29
2,099
275
1,824
180
10800
0.451
0.22
2,361
413
1,948
240
14400
0.35
0.17
2,448
550
1,898
300
18000
0.3
0.15
2,623
688
1,936
360
21600
0.26
0.13
2,728
825
1,903
480
28800
0.22
0.11
3,078
1,100
1,978
600
36000
0.18
0.09
3,148
1,375
1,773
720
43200
0.14
0.07
2,938
1,650
1,288
1080
64800
0.12
0.06
3,777
2,475
1,302
1440
86400
0.085
0.04
3,568
3,300
268
Vs Max = 1,978 cf jMaximum Storage Required
1 hour
2 hours
3 hours
4 hours
5 hours
6 hours
8 hours
10 hours
12 hours
18 hours
24 hours
V sb = 5,205 cf ISeepage Bed Volume (38% Voids)
V sb 15%= 5985.932239 cf Seepage Bed Volume (x 15%)
Depth = 7.3 ft See age Bed Depth Required
Seepage Bed Size = 15 ft wide x 55 ft long x 7.3 ft deep
Vs Max =
1,978 cf
Maximum Storage Required
(1) 1000gal Sand and Grease Trap 6 Amcor Pre Cast
A b =
V sw =
3,956 sf
of 6" deep swale required
1,318.6
sf
V sw=
2,637 sf
of 9" deep swale required
989.0
sf
V sw =
1,978 sf
of 12" deep swale required
659.3
sf
De th =
2.3975 ft
Swale Size=
15
ft wide x 55 ft long x
2.40
ft deep
Velocity
Through Baffle:
T e:
(1) 1000gal Sand and Grease Trap 6 Amcor Pre Cast
A b =
4 sf See appendix D
Q 10 min.
1.55 cfs 100 year Peak Q dev. At 10 min duration
Velocity
= 0.39 ft per sec.
See ace Bed Recove Time (floorl:
V s = 1,978 cf
Q pert = 137.50 cf per hr
Time Rec= 1 14.41 hours
See a e Bed Recove Time 213 sidewalls :
Vs=
1,978 cf
Qerc =
112.87 cfper hr
Time Rec =
17.51 hours
Time Rec =
0.73 days
0.2 landscape (pervious)
Impervious area = 13,625.69 sf 12944.406 sf
Pervious area 27,388.57 sf 8216.571 lisf
Total Area = I 41,014.26 sf I 0.521"C"
of 18" deep swale required
of 24" deep swale required
of 36" deep swale required
MANHOLE FRAME AND
COVER PER IDAHO PUBLIC
WORK5 5TD5. (TYP)
INLET PIPE (SEE PLAN
FOR ORIENTATION)
TOP VIEW
8'-6-
,2--0"
'-6"11
,2 -0" { 4'-6" , 2'-0"
MANHOLE FRAME AND —
COVER PER IDAHO PUBLIC
TO SEEPAGE BED
1NORK5 5TANDARD5. (TYP)
M
GRADE ADJUSTING RINGS 8 -6
w
w_
W r >
INLET PIPE
24" . 3
OUTLET TO
WEIR ELEVATION 3 5EEPAGE BED
sll n
f 3'-4 1/8"
SIDE VIEW
f 8'-0" --�
NTC)T pr%
I. 1000 GALLON PREGA5T CONCRETE BOX USE FABRIGATIOR5 STARDARD
51ZE A5 MANUFACTURED BY AMCOR PREGA5T,
2. INV. IN. > WEIR ELEV. BY I" MIN. UNLE55 OTHERWISE INDICATED ON PLAN5.
3. INV. OUT < WEIR ELEV. BY 3" MIN. UNLE55 OTHERWISE INDICATED ON PLAN5.
1000 GALLON SAND
1 AND GREASE TRAP ll,:,"�