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III IIIIIIIIIIIII III STATE OF COEORApO rannnnuir lord rn ~o:~,,,"~ yy9 DEPARTMENT OP NATURAL RESOURCES O. Monte Pascoe, Executive Director MINED LAND RECLAMATION 423 Centennial Building, 1313 Sherman Slreel Denver, Colorado 80203 Tel. (303) 866-3567 David C. Shelton Director December 2, 1981 TO: Dob Liddle FROM: Roy L. Cox ~). ~ .i/ '•' ~ RE: Adequacy Review of Materials Submitted by Snowmass Coal Company North Thompson Creek Mines - File No. C-025-81 Per your request, I have reviewed the responses to the Preliminary Adequacy Review submitted by Snowmass Coal Company. In my review I have identified numerous concerns which must be addressed prior to formulating written findings and approving a permit under the Colorado Permanent Program for coal. Data received to date from this mine and coal mines within the adjacent North Fnrk bf the Gunnison Basin show that streams develop along fracture and fault lines, that the highest occurance of mine inflows is from faults and fractures associated with the perennial and ephemeral stream channels, that mine inflow rates fluctuate in response to snowmelt and precipitation events, and that mine inflows from faults and fractures are not significantly reduced by sealing in shaley overburden. Even with limited extraction techniques used by the North Fork mines to prevent subsidence under perennial and ephemeral stream, under- ground mining of coal beneath streams does induce stream depletions. Snowmass will mine under an ephemeral stream and adjacent to and under two perennial streams, North and Middle Thompson Creeks. Fractures associated with these stream valleys will contribute inflows to the mines and deplete water in these streams and their alluviums. Mine water is discharged into the North Thompson Creek drainage. Therefore, any water depleted through mine inflows from Middle Thompson Creek will be removed from that drainage system. The effects to downstream users on Middle Thompson Creek have not been addressed within the permit application. The water rights for mine inflow waters which are tributary to both North and Middle Thompson Creeks have not been adequately addressed in the permit application. During mining, the inflow water can be pumped back to the surface and eventually be returned to the surface stream (North Thompson Creek). Ifowever, the quality of water becomes degraded in the movement through the fractures or faults to the mine and wit/zin the mine itself. Soluble contaminants will not be removed in sediment ponds. Therefore, discharges of mine c/aters will impact the quality of surface water within North Thompson Creek, especially during low flow periods.