06.VBF - VOLUME CALCS - 052214Looking at the NRCS Web Soil Survey and Soil Boring/Test Pit data, we find that the soils found on-site are non-condusive to infiltration.
For this project, due to the soils, we are proposing to filtrate 1.1" of the increased hardcover runoff.
Subject: Volume Control - Filtrate 1.1" of Runoff over the Proposed Hardcover
No. of Houses =15 Each
Ave. House Roof Area =2,500 SF
No. of Future Houses =12 Each
Ave. Future House Roof Area =2,500 SF
No. of Driveways 15 Each
Ave. Driveway Area =1,200 SF
No. of Future Driveways 12 Each
Ave. Future Driveway Area =1,200 SF
Area Of HOA Amenity Lots =0 SF
Area Of Street =32,500 SF
Area Of Future Street =19,000 SF
Total Hardcover Area =3.48 Acres
Existing Hardcover Area = 1.75 Acres
Difference =1.73 Acres
Gross Site Area =14.65 Acres
Impervious Ratio =23.7%
Filtration Volume Required:
Required Ffiltration - 1.1 inches = 0.092 ft
Hardcover - 1.73 acres = 75,170 sf
Filtration Volume Required -75,170 sf x 0.092 ft =6,891 cf
Area
Filtration
Depth
Filtration
Volume (cf)
Pond 1 20120 1 20,120
20,120 cf
Drawdown Volume Provided -20,120
Filtration Volume Required -6,891
Difference -13,229 cf
1.1" Volume Control
For this project, we propose to utilize a filtration shelf just above the NWL. An additional 10:1 bench is proposed for one vertical foot above
the NWL. A sand filter with a submerged draintile will allow the runoff to be filtrated and exit through the draintile. See Typical Detail.