Environmental Assessment for Construction of Storm Water Detection System at Storm Water Outfall #3, Malmstrom Air Force Base, Montana
Environmental assessment 28 Aug 2006-28 Aug 2007
AIR FORCE CENTER FOR ENVIRONMENTAL EXCELLENCE BROOKS AFB TX
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The United States Air Force USAF has prepared this EA to assess the environmental and social impacts resulting from the proposed action to construct a storm water detention pond at storm water Outfall 3 planned for late Fiscal Year FY 2007 at Malmstrom AFB. This project proposes to construct a storm water detention pond at Malmstrom AFB storm water Outfall 3 to address flooding and erosion issues historically experienced at that outfall improve water quality at the discharge boundary of Malmstrom AFB and control peak flow discharge rates. Outfall 3 is one of 9 outfalls discharging storm water runoff from Malmstrom AFB. It is located on the north boundary of the base discharging water into the Middle Fork of Whitmore Ravine. The detention pond will detain water from the 10-year 24-hour storm to prevent erosion, provide settling of sediments before discharge, and control the 10-year 24-hour storm event peak flow at the proposed site. Additional design parameters used in the design of the proposed pond include the City of Great Falls Storm Drain Design Manual definition of the hourly precipitation distribution for a 10-year 24-hour storm a maximum discharge rate from the detention pond of 12.9 cubic feet per second cfs in order to maintain predevelopment peak flow rates from the 100-year 2-hour storm and a maximum slope of 31 for the old Milwaukee Railroad fill. The proposed pond will store approximately 494.700 cubic feet of water and reduce outflow to the Middle fork of Whitmore Ravine to 12.9 cfs. Construction of the pond will require approximately 10,400 cubic yards of material to be excavated. The 341st Civil Engineer Squadron 341 CESCEV will determine the location of the storage site for excavated clean fill material prior to construction.
- Hydrology, Limnology and Potamology
- Water Pollution and Control