Prelim Drainage Calcs 001YELM PLAZA
PRELIMINARY DRAINAGE CALCULATIONS
BASIN'A' COVERAGE SUMMARY
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Im ervious Sidewalk andParkin Lot 0.472
Im ervious Roof Area 0.202
Pervious Landsca ing 0.126
BASIN 'A' WATER QUALITY CALCULATIONS
Minimum Stormwater Treatment Area Required:
StormShed software was used to model the runoff from the tributary on-site parking lot, sidewalk
areas, and pervious landscaping. The 6-month storm event resulted in a peak volume of 1,826 cf.
The DOE manual, section III-4.3.2, requires that "the permanent pool volume equals the runoff
volume from the 6-month, 24-hour design storm" Therefore, using 182 LF of 4-foot diameter pipe as
a wet vault, with across-sectional area of 10.11 sf at a 3-foot depth, results in an available pool
volume of 1,840 cf, which exceeds the required volume of 1,826 cf.
Roof runoff is theoretically clean runoff and shall be routed directly to [he infiltration facility bypassing
treatment.
See the following S[ormShetl modeling output.
BASIN'A' WATER QUANTITY CALCULATIONS
`See attached StormShed software output
50' long x S' wide z 4' deep infiltration gallery with three 12" diameter pertorated pipes
Void ratio = 0.30
[(50')(8')(4 -(3)[(50')(3.14)(1'^2)l4]] (0.3) +(3)[(50')(3.14)(1'"2)/4]
Total Storage Volume Provided = 563 cf Mive storage in wef vault not included
Active Live Volume = 550 cf at Elev. = 344.93' per StormShed modeling
563 c!> 550 cf OK
48 Hour Drawdown:
(50' x 8')(20 in/hr)(1'l12")(48 hours) = 32,000 cf> 563 cf OK
5/26/2006 Olympic Engineering f of 4
STORMSHED
HYDROLOGIC MODEL OUTPUT
Note: Onsite Basin A has a total area of 0.80 acres. For purposes of sizing the wet vault treatment facility
and sizing the infltration gallery, two basins were created in StormShed. "Basin A WO" includes all areas
within Basin A tributary to the wet vault (i.e. parking lot, sidewalks, and landscape islands). "Basin A"
includes the entire basin area including parking areas, sidewalks, landscaping areas, and roof areas since
the entire Basin A shall drain to the infiltration gallery.
Water Qualiri Volume:
Basin A WQ Event Summary:
BasinlD Peak O Peak T Peak Vol Area Method Raintype Event
------- (cfs) (hrs) (ac-ff) ac /Loss
BasinA WO 0.13 8.00 0.0419 O.fiO SBUH/SCS TYPEIA 6mo
Drainage Area: Basin A WQ
Hyd Method: SBUH Hyd
Peak Factor: 484.00
Storm Dur 24.00 hrs
Area CN
Pervious 0.1260 ac 40.00
Impervious 0.4720 ac 98.00
Total 0.5980 ac
Supporting Data:
Pervious CN Data:
Pervious Landscaping 40.00
Impervious CN Data:
Impervious parking 8 sidewalk 98.00
Pervious TC Data:
Fiow type: Description:
Sheet Runoff from Landscaping
Impervious TC Data:
Flow type: Description:
Sheet Runoff from parking 8 sidewalks
Loss Me[hod: SCS CN Number
SCS Abs: 0.20
TC
0.03 hrs
0.02 hrs
0.1260 ac
0.4720 ac
Length: Slope: Coeff: Travel Time
10.OOft 2.00% 0.1500 1.92 min
Length: Slope: Coeff: Travel Time
50.00 ft 1.00% 0.0100 1.05 min
Water Quantity:
RLPCOMPUTE [LP] SUMMARY
6 mo MatchO=PeakO= 0.1924 cfs Peak Out O: 0.1862 cfs -
2 yr MatchO=PeakO= 0.3170 cfs Peak Out O: 0.2276 cfs -
70 yr MatchO=PeakO= 0.4875 cfs Peak Out O: 0.3081 cfs -
100 yr MatchO=PeakO= 0.6565 cfs Peak Out O: 0.3962 cfs
Summary Report of all RLPooI Data
Project Precips
[2 yr] 2.00 in
[5 yr] 2.50 in
[10 yr] 3.00 in
[100 yr] 4.00 in
[6 mo] 1.28 in
Peak Stg: 341.02 H -Active Vol: 2.65 d
Peak Stg: 341.79 tt-Active Vol: 110.28 cF
Peak Stg: 343.29 ft-Active Vol: 320.36 c1
-Peak Stg: 344.93 ff -Active Vol: 550.29 cf
5/26/2006 Olympic Engineering 2 of 4
BASLIST2
[Basin A] Using [fYPE1A] As [6 mo]
[Basin A] Using [rYPE1 A] As [2 yr]
[Basin A] Using [rYPEtA] As [10 yr]
[Basin A] Using [fYPE1A] As [100 yr ]
LSTEND
BasinlD Peak O Peak T Peak Vol Area Method Rainiype Event
(cfs) (hrs) (ac-H) ac /Loss
BasinA 0.1924 8.00 0.0598 0.80 SBUHISCS TYPEtA 6mo
BasinA 0.3170 8.00 0.0997 0.80 SBUHISCS TVPEIA 2yr
Basin A 0.4875 8.00 0.1555 0.80 SBUHISCS TYPEIA 10 yr
BasinA 0.6565 8.00 0.2121 0.80 SBUH/SCS TVPEIA 100 yr
BASLIST [rYPE1A] AS [6 mo] DETAILED
[Basin A]
LSTEND
Drainage Area: Basin A
Hyd Method: SBUH Hyd Loss Method: SCS CN Number
Peak Factor 484.00 SCS Abs: 0.20
Storm Dur 24.00 hrs
Area CN TC
Pervious 0.1260 ac 40.00 0.03 hrs
Impervious 0.6740 ac 98.00 0.02 hrs
Total 0.8000 ac
Supporting Data:
Pervious CN Data:
Pervious Landscaping 40.00 0.1260 ac
Impervious CN Data:
Impervious parking, sidewalk, 8 roof 98.00
Pervious TC Data:
Flow type: Description: Length:
Sheet Runoff from Landscaping 10.00 ft
Impervious TC Data:
Flow type: Description: Length:
Sheet Runoff from roof, parking, sidewalks 50.00 ft
HYDLIST SUMMARY
0.6740 ac
Slope: Coeff: Travel Time
2.00% 0.1500 1.92 min
Slope: Coeff: Travel Time
1.00°/ 0.0100 1.05 min
[out 6mo] [out 2yr] [out 10 yr] [out 100 yr]
LSTEND
HydID Peak Q Peak T Peak Vol Cont Area
------- (cfs) (hrs) (ac-ft) (ac)
om6mo a19 e.oa o.osss os7ao
out 2yr 0.23 8.25 0.1000 0.6740
out 10 yr 0.31 8.25 0.1557 0.6740
out 100 yr 0.40 8.25 0.2118 0.8000
STORLIST
[GALLERY-STORAGE]
LSTEND
5/26/2006 Olympic Engineering 3 of 4
Node ID: GALLERY-STORAGE
Desc: DRAINROCK GALLERY STORAGE
Start EI: 341.0000 k Max EI: 345.0000 k
Contrib Basin: Contrib Hyd:
Lengfh Width Void Ratio
50.0000 k 5.0000 k 35.00
DISCHLIST
[INFIL-SURFACE]
LSTEND
Control Structure ID:INFIL-SURFACE -Infiltration control structure
Descrip: BOTTOM OF GALLERY INFILTRATION SURFACE
Start EI Maz EI Increment
341.0000 k 345.0000 k 0.10
Infil: 20.00 inlhr Multiplier: 7.00
5/26/2006 Olympic Engineering 4 of 4