06.LaMettry - Volume Calcs - 061815Subject: Volume Control - 1.1" Abstraction of Runoff over the Proposed Hardcover
North Building =18,300 Each
North Parking =21,600 SF
South Building =22,150 Each 40,450
South Parking =28,200 SF 40.45
Total Hardcover Area =2.07 Acres
Existing Hardcover Area = 0.0 Acres
Difference =2.07 Acres
Gross Site Area =23.11 Acres
Impervious Ratio =9.0%
Abstraction Volume Required:
Desired Abstraction Depth - 1.1 inches = 0.092 ft
Hardcover - 2.07 acres = 90,250 sf
Abstraction Required - 90,250 sf x 0.092 ft = 8,273 cf
Hydrologic Soil Group:B Provided by the NRCS Web Soil Survey
Assumed Infiltration Rate: 0.3 in/hr
Drawdown Requirement: 48 hr
Maximum Abstraction Depth: 1.2 ft
Abstraction Credits:
North Chambers 3395 cf of dead storage
Middle Chambers 3214 cf of dead storage
South Chambers 1913 cf of dead storage
8522 total cf of dead storage provided
Dead Storage values taken from HydroCAD storage tables.
Volume Control
Underground Stormwater Treatment will be provided using the Cultec cystem with chambers and crushed rock, as spec'd by Cultec and
Royal Enterprises. We have limited the proposed dead storage to the Maximum Abstraction Depth as indicated above. Three chamber systems will
be used to meet the stormwater requirements for this project.