PE-1885 PRAIRIE ORCHARD DRAINAGE REVIEW FINAL REVISED REPORT
CLC A55OCIATES
D E N V E R
5 P 0 K A N E
5ALT LAKE CITY
F Pwi-Sed
dmimia
Nfor~-
~~,~~t043
i
I
URAINA~E REPO:RT
for
Prairie Orchard
,i
L7Rr41NAGE REPC]RT
for
Prairie Orchard
Spakane County, Washingtnn
June 2003
CLC J06 #50201 6fl
The tfesign improvemen#s shvwn in fhis set c~f plans and calculatians canfvrrn tv the
applicabie editigns of the Spokane GQUnty Standards far Raa+d and Sewer
Canstructivn and fhe Spokane +Gnunty Guidelines for Starm Water Management. Alf
these pla desigr~ de►~iatit~ns haae f~een approved l~y the Spokane Cau~aty Engineer. I approVe
ns (calculations) far canstructinn.
This repvrt has been prepared by+ the staff of CLG Associates, fnc. under the direction of
the undersigned professFOnal engineer whQSe seal and signature ap hereon.
.
~
~
i - ~
I EXPIRES 9/24;
, T[]dd W hlpplE, P. E.
i;
i
PRAIRIE ORCNARD
L]RAIII►A GF N►4 RRA T! VE
_ GENERAL ,
This project is on the Prairie Orchard preliminary plat. The site has ara existing residentiaf home
on lat 7. The remainder of the site is vacant with field grass as the predominant land cover and
uegetation. The project site is [ncated on the north side of 24t" Avenue between Adams Raad
and Pragress Road in Spokane Caunty, Washingtan.
PUR,PQSE
The pGrpose of this report is to delermine the extenf of storm drainage facilities which will be
required to dispase of the increase in starmwater runaff created by the deuelopment of the
Prairie ❑rchard plat. The storm drainage facilifies vn thrs project have been designed to dispQSe
of runaff fr4m a ten-year design storm, as required by the Spnkane County Graidelines for
- Stormwater Management, (GSM). Calculations are also included t❑ ipustrate the extent of
Grantainmenf for tne 1 0- and 50-year storm events
This development is within the Aquifer 5errsitive Area of Spakane County and is therefore
suhject to `208' requirements. Fvr this project, the 10- and 50-year intensity curves from the
5prakane, Medir-al Lake, Reardon, Cheney, and Rackfvrd areas were ussd, as welf as the SC5
isa-pfuviaC rainfalE curves.
AIVALYSIS METH[3DOLQGY
Per the GSM, the Rationaf Method, which is recommended For basEns less than ten acres an
size, was usetl to determine #he peak discharges and runoff volumes for all ❑nsite hasins.
PR(]JECT DESCRlPTlO1"J
The Praine C]rchard pla# is a 2.34-acre develapment of 7 single-family residentiaf lats. Prairie
- archard is Eacated in Section 26, T. 25N., R. 44 E., W.M. within Spokane Caunty, Washington.
TOPaGR►4PFIY
The sete generally drains tv the southeast at slapes rangirag frorrr D to 15 percent The Norkhenrest
comer of the site is extremely flat and generally drains to the nor-th-norihwest at slopes under 2
percent. The runofF from this nordhwesterly portian of the site will be canveyed tn a prvposed
pond an Lot 3 of the Prairie Orchard final plat. The runoff from the remainder of the projeCl will
be canaeyed to a praposed porad on LDt a of the Prairie ❑rchard final plat.
SOfLS
As can be seerr frvm the accompanyirag sowls map from the Spvkane Gounty 5oils 5urvey as
perFQrr-ned by the Soil Canservation Service (5CS), thE Slfe CC3n515fi5 of 5i]115 Wltfl the GIaSS B
type Tfle soil type is described as foll❑ws.
CLC Assflciates, Inc. 'f Prairie Orchard
GmB - Garrison very gravelly loam, 0 to B percent slopes: SviPs wifhin this type are
somewhat excessively drained soils formed mgravely glacial outwash material from a variety raf
[gneous rack. 5urface runvff is rnedium, and svrl holds Iess then 5 inches of water that plants
can use. GSM Andicate this tv be a 5nib Group Type B and pre-appraved f+or drywel6
installafion.
DRA1NA GE lVARRA T1 VE
- offsite
Based upon the generaE geographic fendencies sur°vunding this sete, no vffsite f9ows are
expected.
Onsite
A4l runvff wEthin the drainage basin will be cvCiected arrd treated using the '20$' runvff methvd as
described in the GSM. Frvm high points in the prvposed road improvementse de51gf1f.'d inlet
IQCatIonS afld fF1e a55LIR1Bd IOt g!'c.'~dIGIg, the proposed Prairie archard plat was divided inta five
basins {1, 2, 3, 4, and 5}. Basirt infarmativrr is pravided in Table 1.
The contritau6ing runaff fram the impervious street area is designed to flow to dawnstream ponds
by placement of curb iralets, which divert runoff into the grassy `208' ponds for treatrrient. The
runoff from each basm is directed to ponds with+n the plat, with the exception af Basin 4.
Develaping Basin 4 reduces lhe runaff coefficient fram 0.32 to 0.23. The runoff from Basin 4 will
nvt be directed into pQnds beeause af the decrease in runof#. The drainage basins and ponds
are shown vn the basin map at the kaack of this repart.
Tab1e Na. 1- Runoff Caefficient Sumnnary
-.:w~ ~,w5~ „re E'~ • -=r a
ota! ►4~r,ea -~6~.~~ Impe~ious 4 Runoff Coe~cien#
~ Pf ~~SI11 ;~f-~: I~IS a 4t~}~• eeCr:
w5 F~1~1~~
1 w 53,8IW'I1.C4 I 147,950 I .39
2 ~ 19,498f0.45 I 7,500 1 44
3 ~ 31,038110 71 ~ 6,200 f .30
4 ~ 20,75110.48 ~ 2,200 I .23
5 I 6,457I0.15 6,457 I 90
, Comhined 2 and 5 I 22,51 OIp.S2 ~ 10,512 ~ .50
Gombined 3 and 5~ 34,4831(].79 ~ 9,645 I .36
- ~
A
Tatal Impervious Rrea included paved raadway area,1,406 sJ per ronf, and 600 s 6. ~per driveway, ptsnd, and
sidewaEk areas.
B "C" {impervi0us area} _ .90
°C" (landscape area)= 15
, GLC Associafes, Inc. 2 Peairie Qrchard
i
Drarnage Calculatians Sermmary
Bowstring caEcufations haVe been included for individual basfns to determine the extent af storrn
drainage facifities required fvr the 1 Q-year storm event. Weighted "C" Runnff Coefficients were
- cafGUlated fvr each basin of less than 10 acres as required by the Spokane County Gu►del►nes
for Stormwater Managemenf. Table 1 pravides the basin size, tafal impenriaus areas* and
- - runoff coefficients.
PEOvided storage volumes shown in the bowstring calculatians were determined using the pond
bottom areas, 3.1 side slopes and a vne-fvat depth.
`208' Calcula tians
The '208' storags aofume fvr each basin was designed to adequately contain the runoff created
by the frst haff-inch of rainfall upon the street impervioUS areas withFn the basin it serves. The
proVided pond bvttom areas, alang with a water quality treatment to a depth af eight inches with
3:1 s'rde slopes, proVide the tota@ vafume shown. Table 2 summarizes the requirements and
designs af the ponds by basin.
- Table 2 -`208` Area and Volume Summary
WNquideU ' ~~P1Cflmpeio~I _~'Pv dM. A~aide~d
2,3,51A I...3,500 146 I 248 ~ 37(] ~ 86
"f lB I 12,000 500 I 583 f 750 f 119.7 J
j'208' imperviaus area r.onsists of street area and driWeways at 600SF per driveway.
Tofa! 5tarrrrwater 5farage Calculativns
!n addition to the '208' storage requirements, the total stormwater storage for the 14-year design
storm was also considered. Each of the ponds in Prairie C7rchard wiff have the capacity to
contain the required Volume of #he 14-year design storm. In addi#ian, the 50-year design storm
wras als❑ examined to verify that the 50-year event coulci be stored in the pond as designed.
This informatiara is summarized in Tabfe 3.
Cl.C Associates, Inc. 3 Prairie Drchard
i~
Table 3- 5tormwater 5tqrage Volume Summary
+1E~'_~r _-~~-'';e`.' • . . • "~tr.
'4.~x
_ ~r:* • - .'`_.i:~.~y~ar and 50-year Stnrsa~e V'v1rr1~~sumrdnary
- y;, . . - ~~~=ti . - _ , _ ,°~.~..-~~1 s:.'~-'_ ~ - * - . - - ~ _ r~ N = „ . _ - - - .x. _ ~
WReguirRl ~ ~I~S~e~ Rand~.Val'ume~
~3 asir~ Y GF ~ C~ Pdrois~~~da~{CF~:
y . , . ,4:=~
I B 313 590 930 1 double
2,3 and 5 A 95 408 408 2 double
'O`VaEume PrQVided is based an 3:1 side slopes and 1' depth; {Area}(1') +(Perimeter)(1.5 ft1)
1NLET GALCf1LATIONS
anlet calculativns were perfarmed in general accordanee G5M and W.S.D.O.T. Hydraulic .
Manual to determine the runoff receiaed and hy-pass flows far each inlet. By-pass f9ows
caEculated far the inlefs ara cvrrtinuDUS grades were added tQ the following downgrade inlet The
ana1ysis shaws that pond `A'requires one 5' hepe 2 curb inlet, two 6' fYPe 1 curb inEets and three
4' type 1 caarb inlet, Pvnd `C' requires twv 6' type 1 curb infets.
FLQODED W1DTH CALCULRTlDNS
A diagrarn has been attached to the Appendix of this repc+rt depicting lhe worst case for the
flooded widfh caicu6ations. The 50-year starm produced afIooded width of 7.6 feet adjacent to
Pond A.
CpNCLt1SfC3N
As demanstrated by th€ calculatians and body of this report, the storm drainage facilities
provided in this design wilE adequately remoue from the sireets, stnre and dispose af the
starmwatec' fram the site fvr 4he 10-year desFgn storm as required by Spv4cane Caunty.
Calc€alation wvrksheets for the 50-year sform euent have been pravided to evaluate the
perFormance vf the designed drainage facilrties. Additivnally, the required `208' treatment area
is proVided for the runoff from the street imperviaus areas.
CLC Associates, Inc. 4 Prairie Orchard
APPENDIX
MAPS
v°rcTnity Map
5ails Map
DEVELOPED BOWSTRING CALCULATIONS,
1 D-Year ❑esign StQrm
50-Year Storm EVent
inlet Caicu1atiQns
F1ooded Width Ga6culations
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5heet 76 OF SCS SOIL SURVEY {3F SP4KANE CQUNTY
~
~
BOWSTRING CALCULATIONS,
PEAK Fl,(3W GALCULFITIC7N BOWS7RING METFiQO PRQJEGT. Prairie t7rchard
10•Year Design Storrn DETEN'tlflN BASIN C7ESIGN BASIN: 1
❑ESIC;NER SKNi: .
BASIN: 919W50 DATE: 14-Aug-02
Tat. Area ;.~3020Fi 5F 0.79 Acres
.
Imp. Area -;•,'~95_@ 5F Time Increment (mEn) 5
C= 0 52 La+nrns fl 15 Time vF CpnC {rr^iin} 5 45
Imp 0 90 autflvw (cfs)
. Qe5ign Year Flaw 10
CA$E 1 Area {acres} 0 79
Imperaious Area (sq ft) 16950
,MC66~ Ft, Qverland Flow 'C' Faclvr 0 52
Area ' C 0410
Ct= f5R~;01 "208" Imp Area .12,0Of]
L. = 60 ft
n _ AM 0 14 D~ Time Time Inc Intens Q Clevel V09.1n 1Aol C]ut 5torsge
~`e3;•,;,,r.ttS = • ; ; ~a'Q22f~= [m3n] (sec) [rnlhr] (cfs) (cu ft) [cu ft] (cu ft)
5 49 329 305 125 552 329 223
7c ~ 3 17 min, hy Equation 3-2 of Guidslines
5 300 318 130 524 300 224
200'ft aitch flaw 10 800 2 24 0 92 653 600 53
4i 15 900 9,37 073 734 900 -166
Z1 = ~50.Q Far 22 20 12l~q 1 45 0.59 779 1200 -421
Z2 m a~ 5~`~ype B= 1.0 ZS 151~[] 1 21 050 799 1504 -701 -
n= fl.Ddi~fi Rolled = 3 5 30 1800 1 04 0 43 815 1600 -985
5= _ ~,4D90 35 2109 093 037 825 2100 •1275
e10 2400 082 0 34 844 2400 -1555
d= ~3i3}Ft Flaw Width fi 5 Ft 45 2700 074 0.30 852 2700 -1848
50 3000 0.68 028 ' 867 3000 -2133
. 55 3300 064 026 894 3300 -2406
A R Q Tc Tc tatal I Qc 50 3600 061 0.25 928 3640 -2672
0.87 0.07 1.25 2.31 5.49 305 1 25 65 3900 060 0 25 988 3900 -2914
iQ 4200 058 024 1024 4200 -3175
Qpeak far Case 1= 1 25 cfs 75 4500 056 0 23 1058 4600 -3442
80 asvo 053 022 1056 4800 -3734
85 5100 052 021 1110 5100 -399{}
90 5400 0.50 0 20 1129 5400 -4271
GASE 2 95 5700 0 49 0,20 1967 5700 -4533
100 6000 048 0,20 1202 saoo a798
Casa 2 assumes a Time of Cvncentration fess ihan 5 minutes sv that the
peak Flvw = 90(3 18)(Imp. Area) = 1 11 cfs "208" TREATMENT REC3L1[REMENTS
Mmimum °208" Volume Required 500 eG ft
Provided Treatrnent Vviume 5$3 cu ft
So, the Peak flow ivr the Basin is the greater vf the twa fiaws, 1.25 cis ORYWELL REQUlRENfEh4T5 - t{Y YEAR DESfGN STQRM
Minimum Storage Required by 8owstring 224 cu ft
Provided 8iarage Voiume 93I7 cu Ft
1VumGer and Type 4f Orywells Speciiied 0 5ingle
1 Ovub6e
PEAK FLOW CALCULATION PROJECT: Pr~ai;r,i,e O~r~ch-ar~d
10-Year Design Storm
BASIN: 2 a„~nd 5a
Tot. Area -~'2~2;5~1i0`~ SF 0.52 Acres
Imp. Area ~02~SF
C = 0.50 Lawns 0.15
Imp. 0.90
CASE 1
~;~180 ft. Overland Flow
Ct = 0.15
L = 180 ft.
n = 0.400
S = 0.0360
Tc = 5.29 min., by Equation 3-2 of Guidelines
~ 50 ft. Gutter flow
Z1 = For Z2
Z2 = 1.0 Type B= 1.0
n = 0.016 Rolled = 3.5
S = 0.0400
d= 0.10'75 ft. Flow W idth 5.4 ft.
A R Q Tc Tc total I Qc
0.29 0.05 0.78 0.32 5.61 3.02 0.78
Qpeak for Case 1= 0.78 cfs
CAS E 2
Case 2 assumes a Time of Concentration less than 5 minutes so that the
peak flow =.90(3.18)(Imp. Area) = 0.69 cfs
So, the Peak flow for the Basin is the greater of the two flows,
0.78 cfs
PEAK FLOW CALCULATtON PRC7JECT: Prairie L7rch~ar~
1 DEYear []esign StDrm
B A51N: 3 and 5b
- Tvt. Area SF 0.79 Acres
Imp. Area 9,~4{5 bF
~ G ~ 0.36 Lawns 0.15
_ I mp. 0.90
CASE 1
- -0Ift. Duerland FEaw
Ct = 0,.'# a
L = 220 ft.
n = t~3.4tJ0
S = U.0680
Tc = 4.93 min., by Equation 3-2 af Guidelines
11'0 ft, Gutter flow
Zi = Fvr Z2
Z2 = 1.~ Type 6 v 1.0
n= Rolied = 3.5
S = C1.0'~ ~Q
d= 0.13'~ 5 ft. Fiow W idth 6.6 ft.
R R Q 7c Tc tatal I Qc
0.44 0.07 0.84 0.96 5.89 2.95 0.84
C peak for Case 7= 0.84 cfs
CASE 2
Gase 2 assumes a Time vf Concentration iess than 5 minutes so that the
peak flow =.90(3.18)(lmp. Area) _ 0.63 cfs
5o, the Pea'k flow fvr the 6asin ss the grea#er ❑f #he tvvo flvws,
' 0.84 cfs
F'EAK FLOW CALCL2LATIOM PROJECT:0.Pr~°""~airi,e ~r,cf~ar,d 8DW5TRiNG METHDp PROJEC7 Prairfe Drchard
9'0-Ye7i` DeSign SioffTl C3ETENT9pN 6ASIiV DE51GAl HR51N• 2. 3, and 5
DESIGNERQKAI
BA51N. 2, 3, and 5 f]ATE• 2~-Jurr-03
Tot Rrea 56 993 SF 1 33 Acres
Imp Area 20,157 SF Time Increment (min) 5
C~ 0,42 Lawns 0 15 Time of Canc. (min) 500
Irnp, 0.90 (]utflow (cf5) 2
Design Year Flow 10
°
CASE 1 Area (acres) 1 31
Impervious Area (sq ft) 20957
~ 1`80 ft C}verland Flaw 'C' Factvr 0.42
Area ' C 0.543
Ct = ~.15 "708" Imp Area 3,500
L = 180 (t '
n m p,p1fi Time Time Inc Intens. Q DeVel, Vtal In Val.Qut Stvrage
5 = t} OBBi]' (min) (ssc) [inlhr] (cfs) (cu ft) {cu it) {cu ft}
500 300 3.18 1 73 695 600 95
1'c = 0.63 min., hy Equatron 3-2 af Guidehnes
5 360 318 1.73 695 600 98
20[1 ft. Gutter flow 10 6[}0 2.24 1 22 854 9200 -346
15 900 1 77 0.96 964 1000 -836
Zi = 50.0 For 22 20 1200 1 45 0 79 1026 2400 -1374
Z2 = v Type B= i 0 25 1500 1.21 0.66 1053 3000 -1947
n= 0.016 Rofled = 3.5 30 1800 104 0 57 1075 3600 -2525
5= 0.0,1,60 35 2100 0.91 0.49 1088 4200 -3111
40 2400 082 045 1115 4800 -3685
d= 0 1722 ft. Flour Width 8.6 it. 45 2700 0.74 0.40 1127 • 540(} 4273
50 3000 [}.68 0.37 1146 6000 4854
55 3306 0.64 0.35 1183 6600 -5417
A R 0 Tc Tc tvtal I Qe 60 3600 0.51 0 33 1227 7200 -5973
076 4 09 1.73 1 46 500 3 18 1.73 65 3900 0 64 0.33 1365 7840 •5495
70 4200 058 032 1356 8400 •7044
Qpeak tor Case 1- 1.73 cfs 75 4500 0.56 030 1400 9000 -7600
80 4800 0.53 029 1412 9600 -8188
85 5160 0 52 028 1470 10200 -8730
90 5400 050 0.27 9495 16800 -9345
CASE 2 95 5700 049 0.27 1545 11400 -9855
r--~---- 100 6040 0 48 [}.25 1591 12130(] -10409
Case 2 assumes a Time af Cvncentration lass than 5 minu[es so that tha
peak flow = 90(3 1 S)(Imp Area)= 132 cfs "208" TRERTMEiVT REQUiREMENTS
V4iinimum "248" Volurne Required 146 cu ft
Provided 7reatment Volume - Rond A 248 cu ff
Sa, the Reak flaw fvr the Baskn is the greater of lhe t+nrn flows,
1.73 Gf5
pR4'WELL REQl11REMENTS - 16 YF_AR DESlGN SfiC}RN1
Minlmum Stflrage Fdequirsd by Bvwstnng 95 cu ft
ProVidsd 5torage Volums - Pond A ~cu ft
Number and Type at Drywells Specifed 0 5ingle
2 DouGle
°
P'~AK FLC~W CALGULATI~C7~1 PRt]JEGT: ~'r~air_
10-Year Qesign 5tvrm
B AS IN: 4 Tot. Area 20';7 e1v SF 0_48 Acres
_ lmp. Area 800 SF
C T 0.32 meadow 0.30
fmp. 0.90
CASE 1
• - 2~0, ft. Overia nd Flow
ct
, L = 220 ft.
n
S = [3:,~28(3:
Tc = 6.44 min., by Equatian 3-2 of Guidelines
. : 0 ft. Gutter flaw
ZI = 50:o For Z2
- - Z2 - .50:,Q TYPe B = 1.0
n- r 0-0-1~.6~- RaNed - 3.5
S-
;r~a«:zQ~aoR
d- 20ft. FEaw 1Nidth 2.5 ft.
.
A R Q Tc Tc total I Qc
0.12 0.02 0.43 0.00 6.44 2.81 0.43
, Qpeak fvr Case 1= 0.43 cfs
CASE 2
Case 2 assumes a Time Qf Concentration less than 5 minutes sQ that the
~ peak flow =.90(3.18)(imp. Area) _ 0.0 5 cfs
~a I So, the Peak flow far #he Basin is the greater vf the two fEaws,
~ 4.43 cfs
-ry~•__- -a- -Y,s;'~-•-r_-k~~"rr[,.~
PEA,'~ FLC3W CALCULATIDN PF~Q.~ECT:'.P~~air
10sYear Design Starm
BAS I N:
Tvt. Area , 2V,T51 5F 0.4$ Acres
lmp. Area ;2[}0 SF
C = 0.23 Lawns 0.15
6mp. 0.90
CAS E 1
220 it. Over6and Flaw
Ct -.0:15
L = 224 ft.
n - 0.40
5 - 8[3
Tc = 6.44 min., by Equativn 3-2 of Guidelines
4 ft. +Gufter flow .
z1 = ° 50.0 Far Z2
Z2 - =50:0 TYPe 8 = 1.0
n Rvlled - 3.5
f~L•
~ - , ,A,Y•~V~ll,
d_ f t. Flow W idth 2.2 ft.
- A R Q TG Tc 1otal I CZc
0.09 0.02 4.31 0.00 6_44 2.81 0.31
Qpeak for Case 1 = 0.31 cfs
CASE 2
Case 2 assumes a Tirne vf Concentration less than 5 minutes so that the
peak flow =.90(3.1'8)(Imp. Area) = 0.14 cfs
So, the Peak flow for #he Basin is tFre greater of the two flows,
{].3'J cfs
F'EINK FLC]W CALCl1LATlON PRQJEC7 ~,Pr~airl,e`~Q~rCh~'r~d~ 8DW57RIN[; METHOCa PRqJECT, Prairie c~rchard
50-Year Design Storm DETErvT1DN aAS1w QEsiGN BASirv ~
~ - DESIGNER<SKIVIIr.";"';,-
, BA$lN DATE 14-Aug-02
Tat Area 4~20~ 5F a 79 Acres
Imp. Area ;~;r146;9_5,~}~5F ,T Time Incremen# (min) 5
~ Time of Ganc {min} 5 28
C= 052 Lawns 015 ~i autflaw (cfs) ' A.1,
Imp. 0.90 •❑esign Year Floru 50
CASE 1 Area {acres} 0 79
----=FT= lmpervfvus Area (sq ft) 16950
a01 ft C]uerland Ff❑w ~'C' Fackar 052
Area'C 0410
Ct `.1'S~ "'208" I m R, Area
L = 80 ft.
n= 0~401 1"ime Time InE. Intens. Q Devel Vol In Vol Out 5torage
S 1 `p~2p {min} {5ec) (inlhr) [cts) (cu tt) {cu ft} {cu Tt}
5 28 397 450 1 84 783 317 466 l"e = 3 17 mm , Gy Equation 3-2 af Guidelines
5 300 3.18 3 30 524 304 224
f:fZk ft C3ii.Ch flow 10 600 2 24 092 549 600 49
-
15 900 1,77 073 731 900 -169
Z1 = 3~~•~n~~'"w"T q ~
For Z2 ZO 1200 1 45 0 59 777 1200 -423
Z2 = Type 6 = 1.0 : 25 1500 121 050 797 1500 -703
n= 3, p~0 Rolled = 3.5 30 180(3 1,04 0.43 813 1$CJO -987
S= y~3 935 2100 091 0.37 823 210[} -1277
_ rua.._~.....
40 240(} 6 82 034 842 2404 •1558
d= °''~'~0 1f6~4 ft, Flvw Width 7.6 ft 45 2760 0 74 030 851 2704 -1849
50 300(] 068 028 856 31704 -2134
55 3300 0 64 0.26 893 3300 -2407
A R Q TC TC total l QC 60 3600 061 25 926 3600 -2674
1.16 0,08 1 83 2 10 5 28 4M i 84 65 3900 060 025 985 3900 -2815
70 4200 058 {}24 1023 4200 -3177
Qpeak For Gase 1 ~ 1 84 cfs 75 4500 0 55 0 23 1057 4500 -3443
SD 4800 053 022 1065 4800 -3735
~85 5100 052 0 21 1109 5100 -3991
90 5400 050 0 20 1128 5400 -4272
CASE 2 95 5700 049 020 1166 5700 -4534
1€70 6000 048 020 1201 6000 -4799
Gase 2 assumes e"f+ms ❑f Cvncentration dess than 5 minutes sv that the
peak flow = 90(4 58)(Imp Area) = 1 60 cfs "208" TREATMENT REDLIIREMENTS
R+1inimum °208" Vo9ume'F7equired 500 eu ft
Provided Treatment Vplume 583 cu it
So, the Peak flow for the Basin i5 the greater af the twc7 flr3ws,
1.84 Cfs DRYWELL REC]L1lFtEMEHTS - 50 YEAR ❑E51GN STCJRM
Minimum Storage Required by Bowstnng 465 Cu ft
Prouided 5tarage Volume •:93Q; cu ft
Number and Type vf C]rywells Specified Q Sirtgle
I Double
PEAK FLOW CRLCULATIaIV PRO.1ECT: Prairie Orchar,d
50-Year Design 5torm
SASIN: ~ and 5A
Tot_ Area 22,510 SF 0.52 Acres
Imp. Area 10,512 SF
C = 0.50 Lawns 0.15
frnp. 0.90
CAS E 1
180 ft. Overland Flvw
Ct = 0.15
L = 180 ft_
n = a.4QD
S = f].D3fi0
Tc = 5 29 min., by Equatian 3-2 af Guidelines
50 f#. Gutter flow
Z1 = 5[].0 For Z2
Z2 = 1.0 Type B = 1.0
n = 0.016 Rvlled = 3.5
:S = 0.0400
d= 0.1240 fit_ Flaw Width 6.2 ft.
A R Q 3c Tc tvtai E Qc
0.39 0.06 1.14 0.29 5.58 4.42 1.14
Qpeak far Case 1 = 1.14 cfs
C►45E 2
Case 2 assumes a Time of CvnCentratian less than 5 minu#es sa tha# the
peak flow =,90(4.58)(Imp. ,F1rea) = 0.99 cfs
Sa, the Peak flow for the Basin is the greater vf the two flows,
1.14 cfs
PEAK FL[JW CALGULATIfaN PROJEGT: Prai"rie C]rcnard
50-Year Design Starm
BASlN: 3 AND 5B
Tot. Area 34,483 SF 0.79 Acres
Imp. Area 10,512 SF
C= 0.38 Lawns 0.15
lmp. 0.90
CASE I
220 ft. 4uerland Flvw
Ct ~ - 0.15
L = 22❑ ft.
n = 0.400
S = D.(]68D
Tc = 4 93 min., by Equation 3-2 nf Guidefines
110 ff. Gutter flow
Zi = 50.0 For Z2
Z2 = 1.[] Type B = 1.0
n= 0.01fi RvE1ed = 3.5
S = 0.0160
d = 0,1552 ft. FEvw W id#h 7.8 ft.
A R Q Tc Tc tofal I Qc
0.61 0.08 1.31 0.86 5.79 4.36 1.31
Opealc fvr Case 1= 1.31 cfs
CAS E 2
Case 2 assumes a Time of Cvncentra#ian less than 5 minutes so that fhe
peak flow =.94{4.58}(Imp. Area) = 0.99 efs
Sv, the Peak flow fvr the Basin is the g`ea#er mf the twv flows,
1.31 cfs
PEAK FLQW CALCLJLRTIQN PR[1JEC7 FiraE'ria Circhard Bf]W5TR1N{; METHaC] PRDJEGT: Prairie prchard
50-YBar Design 5tarm C]ETENTION 6ASfIV DESIGN BASIN: 2, 3, and 5
DE51GNER 5KM
6R51N. 2; 3, and 5 DA7E; 9-May-03
Tat. Area 56,993 SF 1 31 Acres
Imp Area 20,157 SF 'Tima lncrement (min) 5
7ime vf Cvnc, (min) 5 72
C = 0,42 Lawns 0. 15 ? dutflvw (cts) 2
Imp 0.90 C3e5ign Year Flpw 50
Area (acras) 1 31
CAS E 1
_r___ Impervivus Area (sq ft) 20157
_"r~18D ft, Dverland Flow ~'C' Factpr 042
Area ' C 0.543
Gt = 0.1'5 ~ '208" imp Area 3,500
L = 180 ff.
n m 0.400 f Time Time Inc Intens. 0 QeVeI Vvi In Vvl Qut 5t~rag~
5= 0 OfiBd {rnin} (SBC) {inlhr} (cts) icu fty (GU ft) (cu ft)
572 343 4 38 2 38 1095 585 408
,I•
,s,,... .
Tc = 4 37 min., by Equativn 3•2 of Guideline5
5 300 4 58 2 49 1040 600 400
2~0 tt Gutt~r flvw 16 fiCa 3 29 1 74 1246 1?{1Q 4$
15 900 2 45 1 33 1353 1800 -447
Z1 = S~:D For Z2 20 } 20a j 98 1 08 1416 24[}0 -984
Z2 = •1.(}, 7ype 8= 1 fl 4~~,, _ 45 1806 1.68 0 91 1476 30[]0 -15 4
n= Rolled = 3 5 30 1804 1 45 0 79 1514 3600 -2090
S= {1;'01'fi~ 35 2100 i 34 0,71 1565 4200 -2634
LtiM~~: t3 40 2400 119 0 65 1 627 4804 -3173
d= a`l 941 ft. Flow Width 5 7 ft 45 2700 1,09 059 1868 5400 •3732
50 3440 1 0 54 1693 6000 -4307
55 3300 a 92 50 1708 6800 -4892
A R a 7t Tc Eatal I QG F, 6 60 3600 0 88 0 48 1777 7200 •5423
4 98 0.10 2 38 135 5 72 4.39 2 38 65 3900 083 045 181 y 7504 -5989
76 4200 0$0 043 1$76 $400 -6524
l, 45[}0 0 78 042 1956 9000 -7044
C~peak for Gase 1= 2,38 cfs
80 48€30 0 75 041 2003 9604 •7597
85 5104 0 73 040 2669 10200 -8131
~A
90 5400 0.70 0,38 2098 10800 -8762
CASE 2 35 570[] 069 037 2181 114[]0 -9219
100 5600 068 4 37 2250 12000 •9740
Gase 2 aasumes a Time of Cancentratton lass than 5 minutes sv that the
peak fl6w =.90(4 58){Imp Area) = 11.91 cfs .,208"TREA7MENT RELdL1iREMENTS
Minimum "248" Voiume Required 146 cu ft
Rrouided Treatment Volume 248 cu f1
Sq, the Paak tlaw fqr the Basin is the greater oF the [wv flows,
2.38 cfs
y~ ❑RYWEL,L REQl91REMENTS - 50 YEAR DE51GN S70RIN
INinimum 5tvrage Required by 6vwstring 408 Gu ft • ~ Prvvided SfOrag2 Vvlum6 -4eft CU ft
~
_ Number and Type ot Orywefls Speciff8d D Q Smgls
a 2 DauGle
.
- PEAK FLOVIf CALCULATION PROJECT: Prairie~~~rclia~dy~
50-Year Design Storm
gASIN' 4 I?RE •
~ Tot. Area 201-751- 5F 0.48 Acres
Imp. Area $[]0 SF
- C= 0 32 rneadaw 0.343
I mp. 0.90
, CASE I _
220 ft. averland Fiaw
Ct = 0.15
' L = 22❑ ff.
n = C].40
S = 0.0.280
- Tc _ 6.44 min., by Equation 3-2 of Guidelines
; fl fit. Gutter flow
Zl = 50.0 For ZZ
Z2 = S+D:O Type B= 1.0
n= O:`:0~ 5• Rolleef = 3.5
S - . , ;'Q,:E72b~.
. - - d 'dF~8Dft. Flow Width 4.4 ft.
A R Q Tc Tc tvtal I Qc
0.39 0.04 0.64 0.00 6.44 4.18 0.64
Qpeak far Case 1= 0.64 cfs
CAS E 2
Case 2 assumes a Time of Cancentratiarr less than 5 minutes sv that the
- peak flow =.90(4.58)(lmp. Area) = 0.08 cfs
50, the Peak flaw for #he Basin is the greater of the twv flvws,
0.64 cfs
o ,
PEAK FLQVl1 CALCl1LATION PRfl,lECT:.Prair
50-Year Qesign 5torm
BASRN. `4d
' Tot. P+rea 20,751 SF 0.48 Acres
frnp. Area , 2;2[l0 SF
C= 0.23 Lawns 6. 15
Emp. 0.90
CA5 E 1
` - 22O ft. Overland FEvw
Gt = 0.15,
L = 220 ft.
n = 0:4fl
5 = D:D20-
Tc = 6.44 min., by Equation 3-2 of Guidelines
0 ft. Gutter flow
Z1 = SQ.o For Z2
Z2 = 5[~.QType B = 1.0
n = 0:616 Ralled = 3.5
5 = . 6:t32{76
d= , ft. Flow Width 3.9 ft.
A R Q Tc Tc total I Qc
0.30 0.04 0.46 43.00 6.44 4.18 0.46
- Qpeak fvr Case 1 _ 0.46 cfs
CASE 2
- Case 2 assumes a TErne of Concentratipn less than 5 mEnutes sa that the
peak flow =.90(4.58){Imp. Area} = 0.21 cfs
. Sa, the Peak f1aw fvr fhe Basin is the greater of the two f4aws,
0.46 cfs
INLET CALCULATIONS
~
~
,
;
Prairie Orchard S020160
Spokane County, Washington 6/20/2003
50-Year Design Storm Enguieer: TRW
CURB INLET CALCULATIONS
on Continuous Grade
Curb Inlet Basin Basin + Gutter Roughness Depth Discharge Inlet By-Pass
Pond Street and Peak Flow By-Pass Slope Cross slope Coeff. Z of Flow per Length Length Flow
Station (cfs) Q S IJZ n n d* Qa/La** La Q- Qa
24TH AVE
A Sta 17+98.11 1.14 1.14 0.0566 0.0210 0.0160 2976 0.11 0.077 6 0.68
24TH AVE
A Sta 18+09.21 0.68 0.0466 0.0222 0.0160 2815 0.10 0.067 6 0 28
24TH AVE
A STA:18+94.47, 1.31 1.59 0.0166 0.0200 0.0160 3125 0.16 0.108 12 0.30
19+09.47, 19+24.47
24TH AVE
A Sta 19+77.80 0.30 0.0188 0.0200 0.0160 3125 0.08 0.056 S 0 02
NO'fE: TYPES l& 2 CURB INLETS
Curb Inlet Depression = 2 in.
' Calculated per Figure 18 of the Spokane County Guidelines
for Stormwater Management .
Calculated per Figure 16 of the Spokane County Guidelines
for Stormwater Management
~
Prairie Orchard 5020134
Spokane Counry, Washington 08/14/02
50-Year Storm Event Engineer: DvR
CUR.B DROP FLOW CAPACITIES
in Sump Conditions
Curb Inlet Busin Basin + Inlet Maximum Maximum By-Pass '
Basin Street and Inlet Type Peak Flow By-Pass* Length Flow Depth** Discharge*** Elow
Station (cfs) . Q (q H a _ Q - Qa _
' Burns cul-de-sac TYPE 2
I Sta 1+81.82 CURB 1.84 1.84 4.00 0.50 4.37 -2.53
NOTE: TYPE 1 CURB INLET TYPE 2 CURB 1NLET Qa = 3.087 * L* H^ 1.5
Curb Inlet Depression = 2 in. Curb Inlet Depression = 2in. Where L= Length of Curb Drop, H= Flow Depth
Maximum Inlet Height = 8 in. Curb Inlet Length = 4 ft.
Maximum Inlet Height = 6 in.
• By-Pass flows from upstream inlets on continuous grades.
Maximum Flow Depth is based on Inlet height
Calculated per Secrion 4-1 of the Spokane County Guidelines ,
for Stormwater Management
CurbOropS
~ FLOODED WIDTH CALCULATION,
- 7.6' FLOW WIDTVi
r I -
Tl'PkCAL ROAD CROS5-SECTfON
CC?LLECTOR ARTERIAL, 2LANE NaN FLODDED 20fVE WlaTH (FT)
16.Q
~
r~
- DITCH CALCULATIONS.
;
~
~
~
' RDAD5IDE aITCH
Wvrksheet for Tra,pezoidal Channel
' - Peoject Descnplion
Worksheet Trapezoidal CharSnt
Flow E3ement irapezvidai Ghannk
- MethQd Mann'sng's Fvrmula
SQIve For Discharge
_ inpul Qata
Mannrngs Cveffic 0 030
Slope 015000 fUft
QePth 0.5[} R
tefl 5ide 51vpe 300 H V
- Righi Side 51vpe 300 !i : W
8[r[1om Widih 200 Ft
FTesu€is
' discharge 516 cts
- Flow Area S S ft=
Wetfed Perimi 516 ft
' Top WEdih 5 QD Si
CnSic;al [7ep[h ❑ 47 fl
Cnlieal 51ope 0019776 [tlfs
Velvcity 295 SYs
ve►oc,ty Head 014 n
Specific EnerF 4.64 ft
Frpude Numtr 4 88
Flaw Type 3wbentical
Prajecl Ergmeer. [3oug E3esmond
un1i11eci fFn2 CLC Assvciates Inc FIowl+Aaste► v6. k1614k]
45J[]9103 03-12 04 PM @ Haeslad Tutellmds. Inc. 37 Brooks3de Road WaterAury. GT 06708 USA (203) 755-1666 Page 1 oi 1
BASIN MAP
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