HomeMy WebLinkAboutDrainage Summary NA-CEN +%N D
MSE 287-075
DRAINAGE SUMMARY
-- EXISTING CONDITIONS
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At present, this site is the abandoned Northside Drive-In Theatre.
Although abandoned, the drainage infrastructure of the area is still
functioning and in relatively good condition. The majority of this 40-acre
parcel drains to the east through the Holiday Hills and Dales Subdivision.
A small portion drains to the south through culverts beneath 99th Street.
Following is a more detailed analysis of the existing drainage condition and
drainage condition in a 'developed" state.
At present, this 40.94 acre site and the 44.53 acres of off-site water
coming onto this site exit the site at two locations. The entire 44.53 acre
off-site area (Basin 1) and 37.94 acres (Basin 2) of the 40.94 acres on-site
exit the site into the Holiday Hills and Dales Subdivision approximately 650
feet north of 99th Street by open drainage swale. The remaining 3.00 acres
lie in the southeast corner of the site and exit to the south through three
18' corrugated metal culvert pipes beneath 99th Street.
Using a 10-year, 6-hour storm and predevelopment condition, the
combined discharge of the 44. 53 acre off-site and the 37.94 acre on-site
areas is 82.4 cubic feet per second. Individually, the 44.53 acre off-site
area has a peak value of 37.9 cubic feet per second, and the 37.94 acre
on-site area has a peak value of 47.7 cubic feet per second. The 3.00 acre
site has a peak discharge of 9.1 cubic feet per second.
PROPOSED CONDITIONS
Using a 100-year, 6-hour storm and post development condition, the
combined discharge of the 44.53 acre off-site and the 37.94 acre on-site is
179.4 cubic feet per second without retention. Upon providing retention
ponds, the peak discharge to the Holiday Hills and Dales Subdivision is
61.54 cubic feet per second, a 25% reduction. The 3.00 acre site has a peak
discharge of 8. 33 cubic feet per second, an 8% reduction.