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iii iiiiiiiiiiiu iii STATE OF COLORADO MINED LAND RECLAMATION DIVISION Department of Natural Resources 1313 Sherman St.. Room 215 Denver, CO 80203 303 666-3567 FA x: 303 632-8106 DATE: January 12, 1990 T0: Iydrology File FROM: Cathy Begej ~ ~[~ RE: Grassy Gap Mine, C-81-039 pF' COQ ti~ - ~~~,+~8 a`~•1~~~ Roy Romer, Gwamor Fred R Banta. Division Director I have reviewed the 1989 Annual Hydrology Report. Water sampling was performed in compliance with the plan, which calls for monitoring surface water sites on the southern and northern ends of the property along Grassy Creek, an alluvial well on the northern end of the property and two spoils wells on a biannual basis. There was no water at the upstream site (SW-3) either in June or October. Historical sampling records suggest that there is a greater likelihood of flow at SW-7 and I would recommend that this site be monitored instead of SW-3, Both sites are located on undisturbed drainages, and although SW-7 is further up in the basin, the operator does not seem to be able to collect any meaningful data at SW-3. Grassy Creek, as represented by SW-4, is a ha rd, magnesium sulfate water with a slightly alkaline pH. Total dissolved solids were 770 mg/1 this year, a reading similar to that observed over the last four years. The sulfate concentration of the water was 333 mg/1, exceeding the domestic standard at 250 mg/1. The alluvial monitoring well, MW-3, exhibits a water of calcium-magnesium sulfate composition. The water is hard and has a neutral pH. Sulfate concentrations of 455 mg/1 exceed the domestic drinking water standard. Sulfate and salinity levels in the well have doubled in the past five years. Total dissolved solids in 1989 were 1,000 mg/1. Only one of the two spoils wells has any water, and even so, it only shows water in the spring. Results indicated that the Pit 2 spoils well is a magnesium sulfate water with a total dissolved solids level of 2,162 mg/1, The water is slightly acidic (pH = 6.1) and very hard. It exceeds domestic standards for sulfate and lead, and exceeds agricultural standards. The iron levels may be attributable to the muddiness of the sample, and the fact th at parameters should have been measured for dissolved species rather than total recoverable. The operator should be notified and the Division should watch the iron concentration in this well. 3018E/scg