REV13448 - Laserfiche WebLink

Home Browse Search

r III III'I IIIIIIIIIII STATE OF COLORADO DIVISION OF MINERALS AND GEOLOGY Depanmenl of Natural Resources 1313 Sherman 51.. Room 215 rl~ Denver, Colorario 80207 ~ ~~~ Phone: 0031 866-3567 II FA%:0031 8328106 DEPARTMENT OF NATURAi RESOURCE September 21, 1994 Roy ROmer Governor Ms. Kathleen Welt Iames S. lochhead Mountain Coal Company FrecunvefJire<~or P. O. Box 591 michael B. Long Somerset, CO 81434 ow~~~nno~reew~ RE: liinor Revision No. 128 (Kid-term Review); West Elk Mine; Permit No. C-80-007 Dear Ms. Welt; The Division has reviewed Mountain Coal Company's (MCC) responses to the Division's preliminary adequacy review, dated July 19, 1994. The following issues, as noted, must be reconciled prior to approval of this minor revision application. The additional comments are presented in the same order as the letter of July 19; however, issues which have been previously resolved are not included. HYDROLOGY 4. The following addresses the SEDCAD design for the small area exemption for the laydown area. A. The Division believes the particle size distribution for watershed 7A, described as North Fork alluvium is incorrect for this area. The soil type in this area according to Map 40 and 41 and referring to Exhibit 27, is Fughes loam, which is a hydrologic group C soil and is described as a sandy clay loam. MCC should revise the model to utilize the particle size distribution for sandy clay loam, rather than North Fork alluvium. B. The unit hydrograph shape for watershed 7A should be medium rather than slow, as the area within the watershed is disturbed. C. The soil erodibility factor (K) for Watershed 7A should be 0.32, which represents a sandy clay loam, rather than 0.15 which represents sand. The model should be revised. D. The control practice (CP) factor for the west side of the lower storage bench, southeast of FW-1 and the east side ~9 ''`y `~