HomeMy WebLinkAboutPapa Murphy's Drainage Calculations "DEERING
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DRAINAGE CALCULATIONS
FOR
PAPA MURPHY'S
LOT 12 BLOCK 2 JACKS PLACE SUBDIVISION
PREPARED BY
CK ENGINEERING, P.C.
CHAD S. KINKELA, P.E.
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Papa Murphy's on Lot 12 Block 2 Jacks Place Subdivision narrative for storm
drain system.
The building and all hardscape for the Papa Murphy's site plus 25 feet of the
future asphalt for lot 11 Block 2 have been accounted for in the drainage
calculations.
The future building on lot 11 block 2 will need to handle the run-off from the
building. The parking lot drainage has been accounted for in the design of this
Papa Murphy's site.
The seepage bed has been sized to treat the 100 year storm event. All other
surfaces such as landscape area have been assumed to be self-contained and will
not contribute to the seepage trench.
A 350 gallon sand and grease trap has been sized to handle the Q1oo flow and
keep the flow over the baffle below 0.50 cubic feet per second.
No groundwater was encountered during construction of the other storm drain
systems on this site. Groundwater will not be an issue or encountered during
construction of this system.
CK Engineering 130o E.State St Suite 102 Eagle,ID 83616
208.869.0590 mobile
chad@ck-engineers.com
June 29, 2015 PROJECT: Papa Murphy's
Lot 12 Block 2
Assumptions for calculations:
Intensity25= 1.4 in/hr for 1-hour storm w/Tc=22.5 minutes
Intensity100= 1.9 in/hr for 1-hour storm w/Tc=22.5 minutes
C = 0.90 for commercial pad
100-year Peak Flow= C * I *A ft3/sec
Runoff Volume = Area of Hydrograph (0.5*Base*Height)
= 0.5 * 1 hr storm(3600sec) * (Peak Flow)
Drainage CB 100-yr 25-yr Runoff
Area (ft2) C-value Flow(cfs) Flow(cfs) Volume
Drain Area#1 7966 0.90 0.31 0.15 563
Seepage Trench#1
Drainage Area = 7966 ft2
Runoff Volume = 563 ft3
15% Sediment Storage = 76 ft3
Storage Volume Required = 639 ft3
Void Ratio = 40
Percolation Rate = 8 in/hr
Trench Width = 8 ft
Trench Depth = 6 ft
Storage/ft= Void Ratio * Depth -1 *Width
16 ft2
Sidewall Perc/ft= Depth-1 *2/3 *2sides * Perc Rate
4.4 ft2
Endwall Perc= Sidewall Perc*Width
= 35.6 ft3
Length Required - Storage Volume- Endwall Perc
Storage/ft+ Sidewall Perc/ft
= 30 ft
Percolation Rate= 8 in/hr
90% Infiltration Time = 90% Storage Volume
Trench Perc Rate*Trench Area
3.7 hours
Sand & Grease Trap#1
Size = DB 350 gallon
Baffle Separation = 7 in
Inside Width = 42 in
Throat Area = Baffle *Width
= 2.041666667 ft2
Velocity= (C value * Intensity* Drainage Area)/Throat Area
= 0.15 ft/sec
CK ENGINEERING, P.C.
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