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• Wells 8P1-U and 11-U have a similar water quality to Wadge coal Well 19-W. All exhibit a Na-HC03 type water with TDS values less than 900 mg/L. Sinee they are all situated along the sou [h west boundary of the permit area (see Exhibit 7-2) and are completed in adjacent strata, it is likely that the strata are hydraulically connected and that local geochemical conditions are responsible for this water type. Trout Creek Sandstone. Well GW-SS-TC is used es the potable water supply for the Seneca II Mine facilities. It displays a Na-SO4NC03 type water (Table 9). TDS values show little annual fluctuation since 1981, ranging from about 750 to 975 mg/l. Spoils. Three wells that are used for monitoring water quality in the spoils above the Wadge Impoundment are 25-5, 26-5, and 27.5. Well 25-5, the upper spoils well, did not have enough water in its casing to sample in October, 1992, but in May, 1993, the sample displayed a MgCa-S04 type water with a TDS value of 5766 mg/l, which is higher than the historic range (4083 to 5160 mg/l, Table 10 ). Samples from Well 26.5, the middle spoils well, displayed a M9C a-S04 type water with an annual average TDS value of 3733 mg/l, which falls within the historic range. Samples from Well 27-5, the bottom spoils cell, • displayed a MgCa-504 type water with an annual average TDS value of 3047 mg/l, which is higher than the historic range (1,805 to 2879 mg/l). TDS values are lowest at the bottom spoils well as a result of dilution of the spoils aquifer water by the Wadge Impoundment. Well 61-5 is completed above Spoils Spring 1!3 (also known es the Spring Creek area), while Yell 62-5 is completed above Spoils Spring M1 (also known as the Cow Camp Creek area). Samples from Wells 61-5 and 62-5 displayed a MgCe-S04 type water in 1993. The annual average TDS value of 3803 mg/l for Yell 61-5 falls within the historic range, while the annual average TDS value of 3603 mg/l for Well 62-5 is higher than the historic range (2852 to 3341 mg/t). Comparison of Ground Water Ouelity to Water Use Standards. The Colorado Department of Health (CDOH) has drafted basic standards for ground water, including standards for agricultural use (i.e., livestock and irrigation). These standards have been summarized and ere presented in Table 11. Parameters denoted with an asterisk on this table pertain to livestock standards, while those not asterisked pertain to irrigation standards. Results of enalyses~ performed on samples obtained from monitoring wells during the 1993 . Water Yeer have been compered to these standards, and the comparison results are presented in Table 12. 7