1992-07-22_GENERAL DOCUMENTS - C1981017

Home Browse Search

-33- The Coal Creek Basin includes a 26.6 square mile watershed and consists of eight tributary streams. The Coal Basin Mines affect six of these tributaries and a 10 square mile watershed area. Sediment loads within this basin are naturally high. This is due to the steep terrain and large volumes of runoff generated primarily by snowmelt. Water quality is good with total dissolved solids concentration less than 500 mg/l . Both North Thompson Creek and Middle Thompson Creek exhibit similar baseline characteristics. Total dissolved solids content is low, generally between 100 and 300 mg/l . Suspended solids content is also low, except during snowmelt situations or thunderstorm events. The Fourmile Creek drainage also exhibits good water quality. Total dissolved solids concentrations average 150 mg/l , while total suspended solids concentrations normally fall below 100 mg/l . For comparisons of selected water quality characteristics, please refer to Table 3. Probable Hydrologic Consequences - Surface Water The Coal Basin mine plan is designed to minimize the impacts on the surface water hydrology of the area. Mid-Continent has designed and constructed water control structures and closed water use systems to mitigate adverse impacts on the hydrologic balance. For more information on the drainage control plan, see Appendix II-B-7 in Volume 3 of the application and Section V of this document. The hydrologic consequences of mining in Coal Basin are expected to be minimal . The applicant's statement of probable hydrologic consequences on page 22.1 of Chapter IV, Volume 7, predicted no affect on the quantity and quality of surface water other than increased sediment loading, but provided no supporting discussion. Therefore, the following is the Division's assessment based upon information contained in the permit application in Volumes 4, 5, and 7. The Coal Basin mine plan is designed to minimize impacts on the surface water hydrology of the region. Drainages from all disturbed areas are routed through one or more of 21 sedimentation ponds. Based on information presented by the applicant, there should be no effects on surface water quality from sediment pond discharge near the mines as long as the ponds are maintained. Total dissolved solids (TDS), major ions, and metal contents are all similar to the receiving stream levels. However, discharge from the sediment ponds near the preparations plant will increase TDS and metallic cation concentrations in Coal Creek. Discharge from the sediment ponds at the preparations plant increases the soluble salt content by an average of 8 mg/l . Likewise, sediment pond discharges from below the tunnel rock pile and the proposed Sutey disposal site will increase TDS and metallic cation concentrations in Coal Creek. The total suspended solids are lower than the receiving stream. This will not lower water quality. The release of sediment deficient waters into Coal Creek should not create any additional downcutting due to coarse alluvium.