25974 STORM DRAINAGE ANALYSIS
11
A ~s
STORM DRAINAGE ANALYSIS
for
AUTUMN CREST FOURTH ADDITION
October 1994
.
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Prenared Bv: SPOKA(VF COU:V~
~INLAND PACIFIC ENGINEERING PRO,dECT # p r 5~„ W. 707 7th - Suite 200 SUBMInAL # ~ Spokane, WA 99204 RETURN Tp Cp~NTY ENGi
(509) 4S8 6840
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BOWSTRING METHOD (TEN YEAR STORM DESIGN) PROJECT: P1570C TIME OF CONCENTRATION (minutes)
DETENTION BASIN DESIGN @ASIN: M
REVIEWER: REICH Tc (overtand) Tc (gutter) Areas "C A'C
NUM9ER OF DRYWELLS PROPOSED DATE; 01-Nov94
0 Single (type A 1 Double (type B) C1= 0.15 L2 = 170 0.99 0.25 02475
Total Area (calc.) (see H1) 0.99 Z1 = 48 0.00 0,00 0
rme of Conc, (calc.) (sae H1) 9,32 L1(A) = 160 Z2 = 0.16 0.00 0.00 0
Composfte'C (calc.) (see Ht) 0.25 N(A) = 0.4 B = 0 0.00 0.00 0
Time of Conc. (min) 9.32 S(A) = 0.01 n ~ 0.016 0.00 0.00 0
Area (Acres) 0.99 s E 0.008 0.00 0.00 0
C Factor 0.25 Tc (A) ~ 1.24 d= 0.135 0.00 0.00 0
Impenious Area (sq. ft.) 4120 NOTE; Only ACP farm 20th Total A Comp "C
Volume Provided 208: 176 slortn: 352 L1(8) = 0 Tc (gu) = 1.48 0.99 0.25
Out(low (cfs) 1 N(B) = 0 Tc(A+B) = 7.24
Area' C Faclot 025 S(B) = 0 Q=C'I'A= 0.59 .
- - 4 Tc(tot.) = 9.32 Q(est.) ~ 0.60
#1 #2 #3 #4 95 96 #7 Tc (B) ~ 0,0 Intertsity ~ 2.31
Time Time tntensity Q dev. V ln V out Storage A° 0•438858
Inc. Inc. WP = 6.6181
(min,) (sec.) (nlhr.)(cfs) (cu. fl.) (cu. 8.) (cu, R.) R ■ o.osp
(#1'80) (A'C'#3) (Outf."1!2) (#5-M V= 1.36
- =z Tc (totah = Tc (overland) + Tc (gullet) Tc(gu) ~ 2.08
9.32 559.49 2.37 0.59 439 559.49 -120 Tc (overland) = Ct'(L1'N/S"4.5)110.6) Q(est) = 0.60
Ct = 0.15
5 300 3.18 0.79 316 300 16 L1= Length of Overland Flow Holding ~ 6.06
10 600 2.24 0.55 438 600 •162 N=(ricGon facla of overland Oow (.4 for average grass cover)
15 900 1.77 0.44 478 900 -422 S= average slape of overland Ilow
20 1200 1.45 0.36 499 1200 -701 Tc (gutter) c Length (fl.)Nelocity (flJsec,)160
25 1500 1.21 0.30 506 1500 •994 B= Botlom widlh of gulter or ditch
30 1800 1.04 0.26 512 1800 -1288 Zt = inverse of crass slope one of ditch
35 2100 0.91 0.23 516 2100 •1584 Z2 = imrerse of cross slope lwo of ditch
40 2400 0.82 0.20 526 2400 •1874 d= depth of Oow in gutter (estimate, check estimate wilh Flow)
45 2700 0.74 0.18 529 2700 -1171 Area = d'B+d"212'(Z1+Z2)
50 3000 0.68 0.17 537 3000 -2463 Wetted penmeter= B'd+(1lsin(atn(121))+1lsin(atn(122)))
SS 3300 0.64 0.16 553 3300 •2747 Hydraurc Redius = R= AreafWetted Perimeter
60 3600 0.61 0.15 572 3600 •3028 Velxity =1.486ln'R".661's"S
65 3900 0.60 0.15 601 3900 -3293 Flow = Velocity'Area
70 4200 0.58 0.14 630 4200 •3510 n= 0.016 (or a5phalt
75 4500 0.56 0.14 650 4500 •3850 s= longitudinal slope of gutler
80 4800 0.53 0.13 655 4800 4145
85 5100 0.51 0.13 681 5100 -4419
90 5400 0.50 0.12 692 5400 -4108
95 5700 0.49 0.12 714 5700 4986
100 6000 0.48 0.12 735 6000 •5265
_
DRAINAGE POND G4LCULATIONS
Required grassy swale pond storage volume
= Impervious Area x.5 in112 inJfl. = 172 cu. ft.
provided: 176 cu. ft. Olq
DRYWELL REQUIREMENTS • 10 YEAR DESIGN S70RM
Mazimum storage required Dy Bowstrin8 = 16 cu. ft.
provided: 352 cu. fl. OK!
Number and type of Diyrvells Required = 0 Single 1 Double
~
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PURPOSE
The purpose of tbis report is to determine the extent of storm drainage facilities
which will be required to dispose of stormwater runoff created by the development of
- Autumn Crest Fourth Addition. The storm drainage facilities on this project will be
designed to dispose of runoff from a ten year design storm. This development is within the
Aquifer Sensitive Area and is subject to '208' requirements.
ANALYSIS METHODOLOGY .
The Rational Method, which is recommended for basins less than ten acres in size,
will be used to determine the peak discharges and runoff volumes.
PROJ'ECT DESCRIPTION
Autumn Crest Fourth Addition is a 24 lot, 8.77 acre subdivision located in Section
26, T 25 N, R 44 EWM. Sheet 76 of the Soil Survev of Svokane Countv, Washington (copy
,
attached) shows that the soil type for the area of the proposed plat is GmB (Garrison very
gravelly loam, 0 to 8% sideslopes), which is somewhat excessively drained and has
moderately rapid permeability.
In the future developed condition, the subdivision will be divided into 9 basins, L
through S, by the crowns and high points of the various road improvements as shown on the
Basin Map included. Basin M includes impervious area from Progress Road which is
included in the peak flow calculations, but is not accounted for in the '208' pond sizing.
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CALCULATIONS
The total and impenrious basin areas used to calculate the times of concentration and
the peak flows for each basin as shown on the pages following are tabulated below.
Total . Impervious :
Basin Area Area Lots DU/GA . Runoff
. (acres) (SF) Coefficient .
L ~t ~r~ ~
M ~ ~ ~ ~i►
N
O ~ ~ ~ ~
P 4op 40P *662M
Q 4ow I" 00~..
R 4woor OF iOV- •~r.,,
R(und) 0.99 , 40.10
S 4mm op-W ~ 4.49
The runoff coefficients shown above were based on the lot density and Table 1 of Spokane
Coun~ G ii elines for Stormwater ManWmn . The lot density was calculated by taking
T,~y
the basin area divided into the number of lots represented in that basin.
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■
PEAK FLOW CALCULATION PROJECT: AUTUMN CREST, FOURTH ADDITION
BASIN: L
Tot. Area Acres
Imp. Area
C
CASE 1
ow ~
Ct
L
S
Tc = 'n., by Equation 3-2 of Guidelines
170 ft. Gutter f low
Z1 = 48.0
Z2 = 0.00
n = 0.016
S = 0.0070
d = 0.130 ft.
A R Q Tc Tc total I Qc
0.41 0.06 0.50 2.28 7.74 2.56 0.50
Qpeak for Case 1= . c s
CASE 2
Case 2 assumes a Time of Concentration less than 5 minutes so that the
peak f low =.90(3.18)(Imp. Area) = 0.27 cfs
So, the Peak flow for the Basin is the greater of the two flows,
INLAND PACIFIC ENGINEERING
,
BOWSTRING METHOD PROJECT: AUTUMN CREST, FOURTH ADDITI
DETENTION BASIN DESIGN BASIN: L
DESIGNER: MWK
DATE: 09/19/94
Time Increment (min) 5
Time of Conc. (min) 7.74
Outf low ( cf s) 0.3
Design Year Flow 10
Area (acres) 0.49
Impervious Area (sq ft) 4120
'C' Factor 0.4
1208' Volume Provided 180
Area * C 0.196
~
Time Time Inc. Intens. Q Devel. Vo1.In Vol.Out Storage
(min) (sec) (in/hr) (cfs) (cu ft) (cu ft) (cu ft)
7.74 465 2.56 0.50 312 139 173
5 300 3.18 0.62 251 90 161
10 600 2.24 0.44 333 180 153
15 900 1.77 0.35 367 270 97
20 1200 1.45 0.28 386 360 26
25 1500 1.21 0.24 393 450 0
30 1800 1.04 0.20 399 540 0
35 2100 0.91 0.18 403 630 0
40 2400 0.82 0.16 411 720 0
45 2700 0.74 0.15 415 810 0
50 3000 0.68 0.13 421 900 0
208' DRAINAGE POND CALCULATIONS
Required 1208' Storage Volume
= Impervious Area x.5 in / 12 in/ft
208' Storage Volume Provided
DRYWELL REQUIREMENTS - 10 YEAR DESIGN STORM
Maximum Storage Required by Bowstring
Number and Type of Drywells Required
0 Double
INLAND PACIFIC ENGINEERING
PEAK FLOW CALCULATION PROJECT: AUTUMN CREST, FOURTH ADDITION
BASIN: M
Tot. Area es
Imp. Area
C = :
CASE 1
verland Flow
Ct = A~
L
n
S =
Tc = 7.24 min., by Equation 3-2 of Guidelines
ow
Z 1 =
Z 2 = 64"P
n = !lwe1.~
S = - ^n7n MMENNOWEEMOO
d = 0.136 ft.
A R Q Tc Tc total I Qc
0.44 0.07 0.57 2.21 9.45 2.31 0.57
Qpeak f or Case 1= 0.57 cf s
CASE 2
Case 2 assumes a Time of Concentration less than 5 minutes so that the
peak flow =.90(3.18)(Imp. Area) = 0.59 cfs
So, the Peak flow for the Basin is the greater of the two flows,
0.59 cfs
INLAND PACIFIC ENGINEERING
_ ,
BOWSTRING METHOD PROJECT; AUTLMN CREST, FOURTH
DETENTION BASIN QESIGN BASIN. M IMPERVIOUS
DESIGNER: MWK
DATE: 09/19f94
Time Increment (min) 5
Time af Conc. (min) 5
Outflow (cfs) 4.3
Design Year Flvw 10
Are~ (acres ) 0.21
Impervious Area (sq f~) 9050
C' Factor 0.9
208' Volume Provided 0
Area * C 0.187
Tinae Time Inc.Intensity Q Devel. . Vol ; In Vol.Out Storag~
(min) (rnin) (in/'hr) (cfs) (cu ft) (cu ft) (cu ft)
5 300 3.18 0.59 239 90 149
_----------,-s_-__---____________-_-.~
5 300 3.18 0.59 239 90 149
10 600 2.24 0.42 294 180 114
15 900 1,77 0.33 332 270 62
20 1200 1.45 0.27 353 360 0
25 1500 1.21 0.23 362 450 a
30 1800 1.04 0.19 370 540 0
35 21Y.70 0.91 0.17 375 630 V
40 2400 0.82 0.15 3[]4 720 0
45 2700 0.74 0.14 38C] 810 0
50 3000 0.68 0.13 394 9V0 0
208' DRAINAGE PON'I3 CALCULATIONS
R~qua,red 12081 Storaqe Volume
= Impervious Area x .5 in ,I 12 inJft 377 cu ft
208f Starage Volume Pravided 0 cu ft
DRYTn7'ELL REQUIR.EMENTS - 10 SCEAR I]ESYGN ST+C)FtM
Maximum Stvrage Required by Bowstring 149 cu ft
Number and Type of Drywells Required 1 Single
0 Dnub1e
"P
re
s~
~P - "
~ t~ f\, ~ . ~ •
1NLAND Pli~~~~C ENGINEERING
_ ■
PEAK FLOW CALCULATION PROJECT: AUTUMN CREST, FOURTH ADDITION
• BASIN: N
Tot. Area 0.85 Acres
Imp. Area 9810 SF
C = 0.35
CASE 1
100 ft. Overland Flow
Ct = 0.15
L = 100 ft.
n = 0.40
S = ' 0.010
Tc = 5.46 min., by Equation 3-2 of Guidelines
280 ft. Gutter flow
Z1 = 48.0
Z2 = 0.00
n = 0.016
S = 0.0142
d = 0.131 ft.
A R Q Tc Tc total I Qc
0.41 0.06 0.74 2.62 8.08 2.50 0.74
Qpeak for Case 1= 0.74 cfs
CASE 2
Case 2 assumes a Time of Concentration less than 5 minutes so that the
peak flow =.90(3.18)(Imp. Area) = 0.64 cfs
So, the Peak flow for the Basin is the greater of the two flows,
0.74 cfs
INLAND PACIFIC ENGINEERING
BOWSTRING METHOD PROJECT: AUTUMN CREST, FOURTH AD INITI
DETENTION BASIN DESIGN BASIN: N
DESIGNER: MWK
DATE: 09/19/94
Time Increment (min) 5
Time of Conc. (min) 8.08
out f 1 ow ( c f s) 0.3
Design Year Flow 10
Area (acres) 0.85
Impervious Area (sq ft) 9810 -
'C' Factor 0.35
1208' Volume Provided 420
Area * C 0.298
Time Time Inc. Intens. Q Devel. Vo1.In Vol.Out Storage
(min) (sec) (in/hr) (cfs) (cu ft) (cu ft) (cu ft)
8.08 485 2.50 0.74 483 145 338
5 300 3.18 0.95 380 90 290
10 600 2.24 0.67 510 180 330
15 900 1.77 0.53 561 270 291 _
20 1200 1.45 0.43 589 360 229
25 1500 1.21 0.36 599 450 149
30 1800 1.04 0.31 608 540 68
35 2100 0.91 0.27 613 630 0
40 2400 0.82 0.24 626 720 0
45 2700 0.74 0.22 631 810 0
50 3000 0.68 0.20 640 900 0
2081 DRAINAGE POND CALCULATIONS
Required '208' Storage Volume
= Impervious Area x.5 in / 12 in/ft 408.8 cu ft
208' Storage Volume Provided 420 cu ft
DRYWELL REQUIREMENTS - 10 YEAR DESIGN STORM
Maximum Storage Required by Bowstring 338 cu ft
Number and Type of Drywells Required 1 Single
0 Double
INLAND PACIFIC ENGINEERING
PEAK FLOW CALCULATION PR4JECT: AUTUMN CREST, FOURTH ADDITION
BASIN: O
Tot. Area 1.14 Acres
Imp. Area 9440 SF
C = 0.30 '
CASE-1- ~
160 ft. Overland Flow
Ct = 0.15
L = 160 ft.
n = 0.40
S = 0.010
Tc = 7.24 min., by Equation 3-2 of Guidelines
280 ft. Gutter flow
Z1 = 48.0
Z2 = 0.00
n = 0.016
S = 0.0138
d = 0.134 ft. ~
A R Q Tc Tc total I Qc
0.43 0.07 0.77 2.62 9.86 2.25 0.77
Qpeak f or Case 1= 0.77 cf s
CASE 2
Case 2 assumes a Time of Concentration less than 5 minutes so that the
peak f low =.90(3.18)(Imp. Area) = 0.62 cfs
So, the Peak flow for the Basin is the greater of the two flows,
0.77 cfs
INLAND PACIFIC ENGINEERING
BOWSTRING METHOD PROJECT: AUTUMN CREST, FOURTH ADDITI
DETENTION BASIN DESIGN BASIN: O ,
DESIGNER: MWK
DATE: 09/19/94
Time Increment (min) 5
Time of Conc. (min) 9.86
Outf low ( cf s) 1
Design Year Flow 10
Area (acres) 1.14
Impervious Area (sq ft) 9440
'C' Factor 0.3 - 1208' Volume Provided 0
Area * C 0.342
Time Time Inc. Intens. Q Devel. Vol.In Vol.Out Storage - (min) (sec) ' (in/hr) (cfs) ('cu ft) (cu ft) (cu ft)
9.86 592 2.25 0.77 610 592 18
5 300 3.18 1.09 437 300 137
10 600 2.24 0.77 614 600 14
15 900 1.77 0.61 667 900 0
20 1200 1.45 0.50 695 1200 0
25 1500 1.21 0.41 704 1500 0
30 1800 1.04 0.36 712 1800 0
35 2100 0.91 0.31 716 2100 0
40 2400 0.82 0.28 729 2400 0
45 2700 0.74 0.25 734 2700 0
50 3000 0.68 0.23 744 3000 0
2081 DRAINAGE POND CALCULATIONS
Required 1208' Storage Volume
= Impervious Area x.5 in / 12 in/ft 393.3 cu ft 208' Storage Volume Provided 0 cu ft
DRYWELL REQUIREMENTS - 10 YEAR DESIGN STORM
Maximum Storage Required by Bowstring 137 cu ft
Number and Type of Drywells Required 0 Single
1 Double
~
INLAND PACIFIC ENGINEERING
PEAK FLOW CALCULATION PROJECT: AUTUMN CREST, FOURTH ADDITION
BASIN: P
Tot. Area 0.88 Acres
Imp. Area 9100 SF
C = 0.40
CASE 1
90 ft. Overland Flow
Ct = 0.15
L = 90 ft.
n = 0.40
S = 0.010
Tc = 5.13 min., by Equation 3-2 of Guidelines
175 f t. Gutter f low
Z1 = 48.0
Z2 = 0.00
n = 0.016 '
S = 0.0069
d = 0.165 ft.
A R Q Tc Tc total I Qc
0.65 0.08 0.94 2.02 7.14 2.66 0.94
Qpeak f or Case 1= 0.94 cf s
CASE 2
Case 2 assumes a Time of Concentration less than 5 minutes so that the
peak flow =.90(3.18)(Imp. Area) = 0.60 cfs
So, the Peak flow for the Basin is the greater of the two flows,
0.94 cfs
INI,AND PACIFIC ENGINEERING
BOWSTRING METHOD PROJECT: AUTUMN CREST, FOURTH ADDITI
DETENTION BASIN DESIGN BASIN: P
DESIGNER: MWK
DATE: 09/19/94
Time Increment (min) 5
Time of Conc. (min) 7.14
Outflow (cfs) 1
Design Year Flow 10
Area (acres) 0.88
Impervious Area (sq ft) 9100
'C' Factor 0.4
1208' Volume Provided 0 -
Area * C 0.352
Time Time Inc. Intens.Q-Devel. Vo1.In Vol.Out Storage
(min) (sec) (in/hr) (cfs) (cu ft) (cu ft) (cu.ft)
7.14 429 2.66 0.94 537 429 109
5 300 3.18 1.12 450 300 150
10 600 2.24 0.79 588 600 0
15 900 1.77 0.62 652 900 0
20 1200 1.45 0.51 687 1200 0
25 1500 1.21 0.43 701 1500 0
30 1800 1.04 0.37 712 1800 0
35 2100 0.91 0.32 719 2100 0
40 2400 0.82' 0.29 735 2400 0
45 2700 0.74 0.26 741 2700 0
50 3000 0.68 0.24 753 3000 0
2081 DRAINAGE POND CALCULATIONS
Required 1208' Storage Volume
= Impervious Area x.5 in / 12 in/ft 379.2 cu ft
208' Storage Volume Provided 0 cu ft
DRYWELL REQUIREMENTS - 10 YEAR DESIGN STORM-
Maximum Storage Required by Bowstring 150 cu ft
Number and Type of Drywells Required 0 Single
1 Double
INLAND PACIFIC ENGINEERING
PEAK FLOW CALCULATION PROJECT: AUTUMN CREST, FOURTH ADDITION
BASIN: Q
Tot. Area 1.29 Acres
Imp. Area 9893 SF
C = 0.25
CASE 1
125 ft. Overland Flow
Ct = 0.15
L = 125 ft.
n = 0.40
S = 0.010
Tc = 6.24 min., by Equation 3-2 of Guidelines
250 ft. Gutter flow
Z1 = 48.0
Z2 = 0.00
n = 0.016 .
S = 0.0119
d = 0.139 ft.
A R Q Tc Tc total I Qc
0.46 0.07 0.78 2.47 8.71 2.41 0.78
Qpeak for Case 1= 0.78 cfs
CASE 2
Case 2 assumes a Time of Concentration less than 5 minutes so that the
peak flow =.90(3.18)(Imp. Area) = 0.65 cfs
So, the Peak flow for the Basin is the greater of the two flows,
0.78 cfs
INI,AND PACIFIC LNGINEERING
BOWSTRING METHOD PROJECT: AUTUMN CREST, FOURTH ADDITI
DETENTION BASIN DESIGN BASIN: Q
DESIGNER: MWK
- DATE: 09/19/94
Time Increment (min) 5
Time of Conc. (min) 8.71
Outf low (cf s) 0.3
Des.ign Year Flow 10
Area (acres) 1.29
Impervious Area (sq ft) 9893
'C' Factor 0.25 1208' Volume Provided 0
Area * C 0.323
Time Time Inc. Intens. Q Devel. Vo1.In Vol.Out Storage
(min) (sec) (in/hr) (cfs) (cu ft) (cu ft) (cu ft)
8.71 , 523 2.41 0.78 544 157 388
5 300 3.18 1.03 412 90 322
10 600 2.24 0.72 562 180 382
15 900 1.77 0.57 615 270 345
20 1200 1.45 0.47 644 360 284
25 1500 1.21 0.39 655 450 205
30 1800 1.04 0.34 663 540 123
35 2100 0.91 0.29 668 630 38
40 2400 0.82 0.26 682 720 0
45 2700 0.74 0.24 687 810 0
50 3000 0.68 0.22 697 900 0
208' DRAINAGE POND CALCULATIONS
Required 1208' Storage Volume
= Impervious Area x.5 in / 12 in/ft 412.2 cu ft
208' Storage Volume Provided 0 cu ft
DRYWELL REQUIREMENTS - 10 YEAR DESIGN STORM
Maximum Storage Required by Bowstring 388 cu ft
Number and Type of Drywells Required 1 Single
0 Double
INLAND PACIFIC ENGINEERING
PEAK FLOW CALCULATION PROJECT: AUTUMN CREST, FOURTH ADDITION
BASIN: R
Tot. Area 1.32 Acres
Imp. Area 10227 SF
C = 0.25
CASE 1
125 ft. Overland Flow
Ct = 0.15
L = 125 ft.
n = 0.40
S = 0.010
Tc = 6.24 min., by Equation 3-2 of Guidelines r
250 ft. Gutter flow
Z1 = 48.0
Z2 = 0.00
n = 0.016
S = 0.0102
d = 0.144 ft.
A R Q Tc Tc total I Qc
0.49 0.07 0.79 2.60 8.85 2.39 0.79
Qpeak for Case 1= 0.79 cfs
CASE 2
Case 2 assumes a Time of Concentration less than 5 minutes so that the
peak flow =.90(3.18)(Imp. Area) = 0.67 cfs.
So, the Peak flow for the Basin is the greater of the.two flows,
0.79 cfs
t
INLAND PACIFIC ENGINEERING
BOWSTRING METHOD PROJECT: AUTUMN CREST, FOURTH ADDITI
DETENTION BASIN DESIGN BASIN: R
DESIGNER: MWK
DATE: 09/19/94
Time Increment (min) 5
Time of Conc. (min) . 8.85
Outf low ( cf s) 0.3
Design Year Flow 10
Area (acres) 1.32 ,
Impervious Area (sq ft) 10227
'C' Factor 0.25
1208' Volume Provided 0
Area * C 0.330
Time Time'Inc. Intens. Q Devel. Vol.In Vol.Out Storage
(min) (sec) (in/hr) (cfs) (cu ft) (cu ft) (cu ft)
8.85 531 2.39 0.79 561 159 402
5 300 3.18 1.05 422 90 332
10 600 2.24 0.74 577 180 397
15 900 1.77 0.58 631 270 361
20 1200 1.45 0.48 661 360 301
25 1500 1.21 0.40 671 450 221
30 1800 1.04 0.34 680 540 140
35 2100 0.91 0.30 685 • 630 55
40 2400 0.82 0.27 698 720 0
45 2700 0.74 0.24 703 810 0
50 3000 0.68 0.22 714 900 0
2081 DRAINAGE POND CALCULATIONS
Required 1208' Storage Volume -
= Impervious Area x.5 in / 12 in/ft 426.1 cu ft
208' Storage Volume Provided 0 cu ft
DRYWELL REQUIREMENTS - 10 YEAR DESIGN STORM
Maximum Storage Required by Bowstring 402 cu ft
Number and Type of Drywells Required 1 Single
0 Double
INLAND PACIFIC ENGINEERING
PEAK FLOW CALCULATION PROJECT: AUTUMN CREST, FOURTH ADDITION
BASIN: R UNDEVELOPED
Tot. Area 0.99
Imp. Area 0 5D `~~Q- "~~~~►N STO¢.M.
C
CASE 1
s
445 ft. Overland Flow
Ct = 0.15
L = 445 ft.
n = 0.40
S = 0.013
Tc = 12.36 min., by Equation 3-2 of Guidelines
140 ft. Gutter f low
Z1 = 48.0
Z2 = 0
n = 0.016
S = 0.0056
d = 0.11 ft.
A R Q Tc Tc total I Qc
0.26 0.05 0.25 2.42 14.79 2.48 0.25
Qpeak for Case 1= 25 c s ~~7
oCASE 2
Case 2 assumes a Time of Concentration less than 5 minutes so that the
peak flow =.90(4.57)(Imp. Area) = 0.00 cfs
So, the Peak flow for the Basin is the greater of the two flows,
0.25 cfs
INLAND PACIFIC ENGINEERING
BOWSTRING METHOD PROJECT: AUTUMN CREST, FOURTH ADDITI
DETENTION BASIN DESIGN BASIN: R UNDEVELOPED
DESIGNER:SPS
DATE: 09/19/94 A\0
Time Increment (min) 5
Time of Conc. (min) 14.79 .
'
Out f 1 ow ( c f s) 0.3
Design Year Flow 10
Area (acres) 0.99
Impervious Area (sq ft) 0
C' Factor 0.10
208' Volume Provided 0
Area * C 0.099
Time Time Inc.IntensityQ Devel. Vol. In Vol. Out Storage
(min) (sec) (in/hr) (cfs) (cu ft) (cu ft) (cu ft)
14.79 887.13 2.48 0.25 292 266.1387 26
5 300 4.57 0.45 182 90 92
10 600 3.20 0.32 255 180 75
15 900 2.45 0.24 291 270 21
20 1200 1.99 0.20 296 360 -64 25 1500 1.67 0.17 298 450 -152
30 1800 1.46 0.14 304 540 -236
208' DRAINAGE POND CALCULATIONS
Required 1208' Storage Volume
= Impervious Area x.5 in / 12 in/ft 0 cu ft
208' Storage Volume Provided 0 cu ft
DRYWELL REQUIREMENTS - 10 YEAR DESIGN STORM
Maximum Storage Requir.ed by Bowstrin 92 cu ft
Number and Type of Drywells Required 1 Single
0 Double
INLAND PACIFIC ENGINEERING
PEAK FLOW CALCULATION PROJECT: AUTUMN CREST, FOURTH ADDITION
BASIN: S
Tot. Area 0.89 Acres
Imp. Area 9173 SF
C = 0.40
CASE 1
95 ft. Overland Flow
Ct = 0.15
L = 95 ft.
n = 0.40
S = 0.010
Tc = 5.30 min., by Equation 3-2 of Guidelines
206 ft. Gutter f low
Z1 = 48.0
Z2 = 0.00
n = 0.016
S = 0.0062 -
d = 0.166 ft.
A R Q Tc Tc total I Qc
0.66 0.08 0.91 2.50 7.79 2.55 0.91
Qpeak f or Case 1= 0.91 cf s
CASE 2
Case 2 assumes a Time of Concentration less than 5 minutes so that the
peak flow =.90(3.18)(Imp. Area) = 0.60 cfs
So, the Peak flow for the Basin is the qreater of the two flows,
0.91 cfs
INLAND PACIFIC ENGINEERING
BOWSTRING METHOD PROJECT: AUTUMN CREST, FOURTH ADDITI
DETENTION BASIN DESIGN BASIN: S
DESIGNER: MWK
DATE: 09/19/94
Time Increment (min) 5
Time of Conc. (min) 7.79
Outf low ( cf s) 1
Design Year Flow 10
Area (acres) 0.89
Impervious Area (sq ft) 9173
'C' Factor 0.4
1208' Volume Provided 0
Area * C 0.356
Time Time Inc. Intens. Q Devel. Vo1.In Vol.Out Storage
(min) (sec) (in/hr) (cfs) (cu ft) (cu ft) (cu ft)
7.79 467 2.55 0.91 568 467 101
5 300 3.18 1.13 455 300 155
10 600 2.24 0.80 605 600 5
15 900 1.77 0.63 667 900 0
20 1200 1.45 0.52 701 1200 0
25 1500 1.21 0.43 715 1:500 0
30 1800 1.04 0.37 725 1800 0
35 2100 0.91 0.32 732 2100 0
40 2400 0.82 0.29 747 2400 0
45 2700 0.74 0.26 753 2700 0
50 3000 0.68 0.24 765 3000 0
208' DRAINAGE POND CALCULATIONS
Required 1208' Storage Volume
= Impervious Area x.5 in / 12 in/ft 382.2 cu ft
208' Storage Volume Provided 0 cu ft
DRYWELL REQUIREMENTS - 10 YEAR DESIGN STORM
Maximum Storage Required by Bowstring 155 cu ft
Number and Type of Drywells Required 0 Single
1 Double
INLAND PACIFIC ENGINEERING
STORMWATER DISPOSAL
BASIN L The peak flow of .50 cfs will be disposed of in a.~Irdrywell in Pond L
BASIN M The peak flow of .59 cfs will be disposed of in a Type "A" drywell in Pond M:
BASIN N The peak flow of .74 cfs will be disposed of in a ell in Pond N. BASIN O The peak flow of .77 cfs will be disposed of in aqPIRMlftrywell in Pond O.
BASIN P Tbe peak flow of .94 cfs will be disposed of in a drywell in Pond P.
BASIN Q T'he peak flow of .78 cfs will be disposed of in drywell in Pond Q.
BASIN R The 10 year peak flow from the developed portion of Basin R requires a Type
"A" drywell and a volume of 426.1 cubic feet.
BASIN S- The peak flow of .91 cfs will be disposed of in a "646grywell in Pond S.
-t~ t4Ev 'Ta Go ~.15 ~ ~ ~
~.n37 ~ Q-~ "g n-S7 . ~ 1k~•v E
' Q-~.Fo'R~~'D -f►k~SE GAa t~S
-rypc ~
P~a~ 5~2~ sv~-o~J
.A
t„> >t-~. ?E A~EQuO~~.
CURB DROP CAPACITY
A.1] of the curb drops and inlets for this project are located in sump condition. The capacity
for a 4' long curb drop and precast inlet are as follows.
Ctiirb Drop
Q = 3.087 L H3/2
L = 4' -
H= for allowable depth outside 12' "dry zone"
_ 12 (0.0233) + 0.17'(2" depression) _0.45'
Q = 3.73 cfs
V~0~`'
Precast Inlet
v ~
Q ~
= 3.087 L H3~2
L=4'
,
H = 14 (0.0208) + 0.17' = 0.46' ~ o
Q = 3.86 cfs o ~
o ~L
0.
,
'208' VOLUME SUMMARY TABLE
' ' •..:i.ti.... . :,v,-. wa.v~~"::::: • . ;4.; - -•F: :w • ' rt,~.;.; '
. . . ~
:.~.~}':5:::::.:.~::::: : . . . :.~::ti•}J.::. ~ ~
. ~ ::v
. . - . v:.~r.. j}'ti}~{:'v:L r_ v. y. :';b''
.
:a''::'""' . . .
. . : : t . t. = •
. • : : : i v~,_ . : • .
' .::.....::::.r.:..::• ~ .:.:F:..ti...~ .
• "'••r'"-- •
OWS~tI~1'G ~~~'208'::~O'Li~iV~E-:P::RQ:
s.~:.
.
~ . - -
:
. . ...t. ..a. . . . . i~..:
: . . . _ . . :
. r
. ~
t~ :
. . : . : iD
. . . .
. N.
. . . . . ~:~r~ ETE
- . . . . . .
. -
. . . _ . .
.
. :
. :
.
: ~ . . . . . ,
. . . : : .
A .
S
. B IN. . CU..
; . ~l•Sa . - .y.~. . . ' . . . ' ' • • " •
._........._Y•.V.•• . ' . _ _ ...J{....`.......'._. _ . . .
L 173
M 149
N . 338
O 49TO'
P
~ . ~ - . . . - .
Q 388 Now
R 402 '
~ N
S
* VOLUME _ (5) AREA + (.375) PERIMETER
~
CURB DESIGN WITff EXISTING PAVING TYPE "B" CURB
Street: PROGRESS ROAD Date: 09/15/94
Project: AOTUMN CREST FOURTH ADDITION Desiqner: 1{ARK
1/2 Paving width = 18.00 ft
FIELD INFORMATION OFFICE CALCULATIONS Existing
Distance Cross 1/2 PW -.Kin Curb. Kin Curb. Froposed Proposed Proposed
Sta. C/L Blev EP Elev C/L Grade C/L to EP Sloge Dist C/L-EP -4.5% -2.0% Curb Elev. Slope Sta. Cross-slope
.3969.70 2054.48 2054.19 18.00 0.0161 0.00 2054.69 2054.69 2054.69 3969.74 ERR
0.0066 0.0030
40U0.00 2054.68 2054.57 10.00 0.0110 6.50 2054.66 2054.83 2054.78 4000.00 0.0270
0.0088 0,0032
4025.00 2054.90 2054.73 10.00 0.0174 6.50 2054.82 2054.99 2054.86 4025.00 0.0393
' 0.0020 0.0032
4050.00 2054.95 2054.74 10.00 0.0210 6.50 2054.83 2055.00 2054.94 4050.00 0.0285
0.0008 0.0032
4075.00 2054.97 2054.82 10.00 0.0150 6.50 2054.91 2055,06 2055.02 4075.00 0.0285
0.0032 0,0036 .
4100.00 2055.05 2054.85 10.00 0.0200 6.50 2054.94 2055.11 2055.11 4100.00 0.0193 ~
0.0020 0.0036
4125.00 2055.10 2054. 94 10.00 0.0160 6.50 2055.03 2055.20 2055.20 4125.00 0.0193
0.0056 0.0044
4150.00 2055.24 2055.10 10.00 0.0140 6.50 2055.19 2055.36 2055.31 4150.00 0.0270
0.0072 0.0060
4175.00 2055.42 2055.27 10.00 0.0150 6.50 2055.36 2055.53 2455.46 4175.00 0.0301
0.0048 0.0040
4200.00 2055.54 2055.39 10.00 0.0150 6.50 2055.48 2055.65 2055.56 4200.00 0.0331
0.0032 0.0040
4225.00 2055.62 2055.48 10.00 0,0140 6.50 2055.57 2055.74 2055.66 4225.00 0.0316
0.0098 0.0040
4250.00 2055.74 2055.60 10.00 0.0140 6.50 2055.69 2055.86 2055.76 4250.00 0.0347
0.0032 0.0032
4275.00 2055.62 2055.66 10,00 0.0160 6.50 2055.75 2055.92 2055.84 4275.00 0.0316
0.0029 0.0032
4300.00 2055.88 2055.66 10.00 0.0220 6.50 2055.75 2055.92 2055.92 4300.00 0.0193
0.0049 0.0041 ~
4324.26 2056.04 2055.76 10.00 0.0240 6.50 ' 2055.85 2056.02 2056.02 4324.26 0.0193
0.0062 0.0070
4350.00 2056.16 2055.98 10.00 0.0180 6.50 2056.07 2056.24 2056.20 4350.00 0.0254
0.0060 0.0060
4375.00 2056.31 2056.12 10.00 0.0190 6,54 2056.21 2056.38 2056.35 4375.00 0.0239
0.0052 0.0060
4400.00 2056.44 2056.24 10.00 0.0200 6.50 2056.33 2056.50 2056.50 4400.00 0.0193
0,0060 0.0060 ~
4425.00 2056.59 2056.39 10.00 0,0200 6.50 2056.48 2056.65 2056.65 4425.00 0,0193
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