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°r <br />~\ MOUNTAIN COAL <br />, \ COMPANVLL.C. <br />A Subsidiary of Arob Wes[ern Resources. LLC P 0 Box 591 <br />5174 Highway 133 <br />Somerset, CO 61434 <br />(970)929.5015 <br />Fax (970)929-5595 <br />The above referenced SEDCAD run utilized sandy clay loam for SWS #1. <br />6. For the Sylvester Gulch fan site SAE, please provide the input values to the RUSLE version <br />1.06 modeling program for the K value of 0.08, the C value of 0.0024 for SWS #1 and the C <br />value of 0.0001 for SWS #2. <br />Since MCC no longer has the information supporting the K and C values previously used <br />for the Sylvester Gulch fan site, the K and C factors were calculated using the same <br />procedures, soil, and vegetation characteristics described above for the raw water intake <br />gallery (No. 1 Comment Above). <br />7. It is stated on page 4 of the TR-92 submittal cover letter that several SAE site designs rely on <br />grass filters for sediment control and that maintenance of these SAE's requires only <br />maintaining the grass filters that are downgradient of the SAE's. In the submittal, the <br />designations for silt fence and straw bales at several SAE's have been removed from Map 54A <br />by this technical revision. <br />Map 54B indicates that the Sylvester Gulch fan SAE is approximately 70ft x 140 ft (0.22 <br />acres) with a steep hill behind it. The attached Calculation Sheet shows a sketch of the <br />SAE. The runoff from approximately 0.8 acres, discharges from the steep hill to the <br />diversion ditch and a concrete curb behind the fan. The ditch carries clear water around <br />the SAE and discharges into the road ditch below the fan site. The remaining area of the <br />SAE is only about 0.1 acre, including the fan housings and the graveled pad. Runoff from <br />this area is contained within a graveled check dam (approximately 1.0 ft high, and 20 ft <br />long on each two sides) to be constructed on the downhill side of the fan, immediately <br />above the road ditch. <br />This Ietter of responses, the two SAE demonstrations with sketch plans, and three revised permit maps <br />(54, 54A, 54B), complete the infonnation for MCC's adequacy responses for TR-92. Please call me if <br />you have any questions. <br />Since ly, <br />enry arbe <br />Environmental Engineer <br />Enclosures: SEDCAD Calculations, Revised Maps 54, 54A, and 54B <br />cc: G. DiClaudio <br />P. Schmidt <br />Availability of Records File <br />Gunnison County Planning <br />Paonia Library <br />-~~ <br />