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1 III ~II~II~II~~II III sss Mountain Coal Company West Elk Mine Post Offce Box 591 Somerset, Colorado 87434 Telephone 970-929-5015 April ]0, 1998 RECEIVED APR 15 1998 Mr. Michael Boulay Division of Minerals 8 Geology Colorado Division of Minerals and Geology 1313 Sherman Street, Room 215 Denver, CO 80203 RE: Technical Revision No. 82 (TLO Improvements); West Elk Mine; Permit No. C-80-007 Dear Mike: Mountain Coal Company (MCC) has reviewed the Division's adequacy letter dated September 11, 1997, regarding the above referenced technical revision and provides the following additional information. MCC must rely on the Contractor to arrange an appropriate construction sequence, but if the existing pond must be removed prior to the construction of the new pond, MCC will require the Contractor to install alternate sediment control measures, such as silt fence, straw bales, or other similar structures. The "sump" at the west end of the trench drain is shown on Drawing 2 and is labeled as "Trench Drain Detail". As you will note from the detail, the sump portion is just a little deeper than the rest of the trench drain. The entire trench drain will capture hydraulic oi] spills. As the State Highway was being constructed at the same time as the TLO, some of the stormwater drainage from this area was included in the CDOT culvert design. MCC met in the field with Ray David and Larry Neal of CDOT to determine if they had any concerns with our continued use of the CMP. They did not. The CDOT culvert is a 24-inch CMP with a grated inlet. The drainage from the road will not change with these proposed improvements, and the discharge structure from the retention pond is sufficiently controlled in a 12-inch pipe. Therefore, the CDOT culvert will continue to be adequate. The outflow from pond MB-4 via the CDOT CMP discharges to the North Fork of the Gunnison River. The Water Quality Control Division has approved an amendment to MCC's CDPS permit to show that discharge point 008 will be relocated further to the west. The amended permit is enclosed and should be included in Exhibit 7.