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~i <br />energy fuels corporation <br />executive offices • suite 900 • three park central • 1515 arepahoe • denver, Colorado 60202.1303) 623-8317 <br />August 28, 1979 <br />Mr. Stanley V. May <br />Engineering Technician <br />Colorado Department of Health <br />Water Quality Control Division <br />4210 East 11th Avenue <br />Denver, Colorado 60220 <br />~~ <br />~ ~, <br />Re: NPDES Permit No. CO-0027154, Routt County <br />Dear Mr. May: <br />• <br />be addressed in order. <br />This letter is written in response to your letter <br />of August 16, 1979, which was received by Energy Fuels on <br />August 21, 1979. Each of your requests for information will <br />1. Sedimentation Pond No. 12, which has now been <br />reassigned the identification letter H, was originally <br />designed to treat runoff occurring as a result of a 10-year, <br />29-hour precipitation event from its watershed based on the <br />anticipated condition of the watershed in the spring of <br />1979. Specifically, when the pond was designed and con- <br />structed, in the summer of 1978, Energy's mine plan con- <br />templated that in the spring of 1979 the surface of the <br />watershed would be a combination of natural vegetation, <br />spoil material and a long box cut, or longitudinal excava- <br />tion. This type of surface condition produces the least <br />amount of runoff and suspended sediment transport of any <br />phase of mining for the following reasons: (1) spoil <br />material has a permeability much higher than that of top- <br />soil, so surface water will infiltrate rather than run off; <br />(2) the roughness of spoil material greatly reduces surface <br />water velocity and, therefore, sediment transports; and (3) <br />most importantly, the box cut intercepts most of the runoff <br />and detains it long enough to reduce substantially the <br />concentration of total suspended solids ("TSS"). <br />• <br />