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a Richard D. Lamm Governor iii iiiiiiiiniu iii 9g9 DEPARTMENT OF NATURAL RESOURCES David H. Getches, Executive Duector MINED LAND RECLAMATION DIVISION DAVID C. SHELTO N, Director DATE: March 12, 1986 T0: Gregg Squire FROM: Dale Plume RE: REVIEW AND CONCLUSIONS REGARDING TWIN PINES MINE ANNUAL HYDRO-GEOLOGY REPORT OR EQUIVALENT Water quality values for some parameters from samples taken in 1985 for the TP-W1 and Caldirola No. 2 Wells show a marked increase in concentration. This trend may be related to a change in the water table elevation going from dryer to wetter and back to dryer years and/or from past historic mining disturbances, or a combination of both these factors. These values should be considered baseline however, as current mining startup has been too recent to have affected the ground water flow, except locally. Well No. TP-W1 shows a steady increase in SAR values to levels (>18), considered detrimental to plant growth if used for irrigation water. Fluoride is increasing to a point in excess of Primary Drinking Water Standards (PDWS 1.4-2.4 mg/1 ). Additionally, trace metals arsenic, boron, cadmium, copper, and iron have increased to the point where these exceed PDWS or Environmental Protection Agency (EPA) and EPA receiving stream standards. These standards may be applicable to the local area around the mine due to the proximity of municipal water supplies; but, the standards only apply to surface waters and not to ground waters. This change in concentration may be due in part or in full to a hange in redox equilibrium caused by c`oncen.ra ton of ions in past low water years and remobilization by exchange processes during more recent high water years. The Caldirola No. 2 Well is showing a similar although not yet high enough to be considered when used for irrigation water. Mid year 198 1985) show an increase in boron, cadmium, and of 2 above PDWS. Fluoride seems to be on the exceeding PDWS as yet. increase in SAR values (9.14) detrimental to water quality 5 water quality samples (June 30, arsenic by as much as a factor increase also, although not Furthermore, current interpretations of the ground water regimen around the mine are in disagreement to those offered in the original permit application. The map submitted with the quarter]y ground water hydrology report letter (dated February 12, 1986) shows what appears to be flow vectors with a directional component pointing to the northeast (approximately 25-300 northeast). If this is the case, then this implies the ground water in or near the coal seam is flowing almost up dip of the synclinal orientation of the strata in the Vermejo formation. Unless a substantial mounding in the ground water levels around the Last Chance mine is occurring then this does not agree with the geohydrologic conditions reported in the original permit application. 423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (303) 866-3567