Runoff Calculations 4-15-05
April 15,2005
RUNOF CALCULATIONS
FOR PARADISE AUTOMOBILE
625 FLYING CLOUD DRIVE, CHANHASSAN, MN.
Site Location: Intersection of Highways 212 and 69 also known as "The Wye" north of
Shakopee.
Area of the Tract: 108021 sq ft (approx.) = 2.48 acres
Area of Proposed Impervious Zone: 108021 x 25% = 27005 sq ft = 0.62 acres
1 inch of rain per day on the total tract sq ft = 1 x 108021 = 0.1042 cfs if all runs off.
(12) x 24 x 3600
Runoff coefficient = 60%
Runofffrom pre-dvlpmt on total tract incl. infiltration. 0.60 x 0.1042 = 0.0625 cfs/inch of rain.
Pre Project Runoff: 10 Year 0.0625 x 4.3 = 0.2688 cfs. 100 Year 0.0625 x 6.0 = 0.375 cfs.
Additional Runoff From New Impervious Area:
New area additional runoff = 0.25 x pre proj. x 0.40
0.60
Additional Runoff:
from Project
! 0 Year
0.0448 cfs.
100 Year = 0.0625 cfs
TOTAL RUNOFF 10 Year = 0.3133 cfs
AFTER PROJECT
100 Year
0.4375 cfs
If you need any further clarification, or if I can be of any further assistance, please do not hesitate
to phone or write.
Sincerely,
. .", /.
ITASCA ENGINEE~Q;,lrnt\~~f~.p.Box 616, Shakopee, MN 55379-0616 Ph: 952-445-7993
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Lawrence E. Samstad, P.1if.JIER .. ~
R~gistered Profession~l~~~ ~t¡
Minn. Reg. No. 6220· . . ~ \\,~".
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CHÞ-N\-IÞ-SSEN
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C\-IÞ-NI-IASSEN PLANNING DE-Pi