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TECHNICAL REPLY TO COLORADO MINED LAND BOARD REVIEW - <br /> . MID CONTINENT RESOURCES, INC. <br /> NOTE: No underground water will go into these <br /> I. Mines 1 & 2 ponds (updated .1986) <br /> A. Underground Discharge - Question I .A (1) <br /> "Sediment Storage Volume (717 . 17 (e) (2) ) <br /> The sediment contained in underground water <br /> discharges into this pond hasn't been estimated. <br /> The pond must be sized to accomodate one year-of <br /> sediment from underground water discharged from <br /> the mine. The current pond has excess sediment <br /> storage of 0. 05 AF (assuming a "K" factor of 0. 35) , <br /> which may provide adequate additional capacity. <br /> However, quantification of additonal sediment <br /> contributed by underground water discharge is <br /> needed. " <br /> The volume of sediment derived from an underground dis- <br /> charge source with variable flows that range from 0 . 1 <br /> to 0.7 cfs and with an estimated average concentration <br /> of suspended solids of 80 ppm is estimated to be 200 to <br /> 1000 ft3 per year. This additional volume is available <br /> in the proposed pond design for Mines 1 and 2 as well <br /> as Mines 3 and 5 . <br /> B. Estimated "K" Factor <br /> "Additionally, if pads 1, 2 and 3 are covered by <br /> coal dust, the K factor of 0. 35 may not be correct. <br /> Other mines have estimated a K factor of .0 .7 for <br /> areas covered by coal fines. Please clarify the <br /> thickness and extent of coal fines on these pads. <br /> Soil erodability factor K is the factor that is used to <br /> estimate susceptibility to erosion in the universal soil - <br /> loss equation. This factor is empirically based on <br /> agricultural data where clay, silt and sand soils are <br /> relatively thick compared to construction and mine pad <br /> areas. <br /> The- "K" factor is a function of degree of aggregation <br /> of soil particles. Large aggregates of soil particles , <br /> • i.e. stony (rocky) soils , are much less susceptible to <br /> J <br /> erosion than finer grained silty and clayey soils. <br /> -1- <br /> 5 4 <br />