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1 <br /> SUMMARY AND CONCLUSIONS <br /> Data, analyses, and conclusions of a hydrologic investigation in the <br /> vicinity of CF&I Steel Corporation's Allen and Maxwell Mines are presented <br /> in this report. These mines are underground coal mines located in Las Animas <br /> County on the Purgatoire River approximately 30 miles west of Trinidad, <br /> Colorado. The study included characterization of the hydraulic properties <br /> of the coal seam, overburden, and alluvium by field and laboratory tests. <br /> A combination of drill holes and backhoe pits were used to investigate the <br /> distribution of alluvium and terrace materials in the vicinity of the Maxwell <br /> Mine. Estimates of eventual inflows to the Maxwell Mine were made and these <br /> were coupled with water quality data on mine and stream discharges to calcu- <br /> late the expected effect of mining on the quality of waters in the Purgatoire <br /> River. A water balance was used to estimate the deep percolation from the <br /> active refuse pile at the Allen Mine. The chemical characteristics of the <br /> subsurface discharge from the refuse pile were determined and the influence <br /> of the waste material on the quality of stream waters was estimated. <br /> Data from this investigation, studies by others, and from the Allen <br /> Mine indicate a very low water-bearing capacity of strata in the Raton forma- <br /> tion. <br /> 1 _ The ground-water inflows to the Maxwell Mine are expected to be on the <br /> order of 180 gpm at full mine development. The source of this discharge <br /> is the coal seam and vertical flow through the overburden in response to <br /> the drawdown caused by the mine. This estimate of inflow is consistent with <br /> the inflow now being observed in both the Maxwell and Allen Mines. Using a <br /> conservatively estimated value for mean low flow in the Purgatoire River, <br /> discharge of this inflow will cause an estimated increase of dissolved solids <br /> in the stream equal to 47 mg/1 . The increase in the average dissolved <br /> solids concentration in the mean annual flow at the Maxwell Mine location <br /> i will be about 13 mg/l . Estimated changes in trace element concentrations <br /> J are very small . Similar conclusions were reached relative to the effect of <br /> current mine discharge from the Allen, the estimated increase in dissolved <br /> solids being 32 mg/l . It is estimated that the combined contribution of the <br /> current Maxwell and Allen discharges and the active refuse pile at the Allen <br /> to the total salt pickup between Stonewall and Madrid is about 2 percent. <br />