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type water (Table 8). The annual average TDS value of 1832 mg/t is above the historic • range. Yells 8P1-U end 11-U have a similar water quality to cadge coal Yell f9-4. All exhibit a Ra-XC03 type water with TDS values less than 900 mg/l. Since they ere all situated along the southwest boundary of the permit area (see Exhibit 7-2) end ere 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. Yell GY-SS-TC is used es the potable cater supply for the Seneca 1[ Mine facilities. It displays a Ne-SO4 XC03 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 Wedge 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, 1993, but in Nay, 1994, the sample displayed a MgCa-504 type water with a TDS value of 5714 mg/l, which is within the historic range (4083 to 5766 mg/l, Table 10). Samples from Well 26-5, the middle spoils • well, displayed a MgCa-504 type water with an annual average TDS value of 3463 mg/l, which fells within the historic range. Samples from Vell 27-5, the bottom spoils well, displayed a MgCa-S04 type water with an annual average TDS value of 3207 mg/l, which is higher than the historic range (1805 to 3047 mg/L). TDS values are lowest at the bottom spoils well as a result of dilution of the spoils aquifer water by the 4adge Impoundment Mall 61-5 is completed above Spoils Spring #3 (also known as the Spring Creek area), while Yell 62-5 is completed above SpoiLS Spring #1 (also known as the Cow Camp Creek area). Samples from Wells 61-5 and 62-5 displayed a MgCa-S04 type water in 7994. The annual average TDS values of 3849 mg/l for Well bt-S and 3680 mg/l for Yell 62-5 are both higher than their historic ranges. Comparison of Ground Water Duality 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 are 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 analyses performed on samples obtained from monitoring wells during the 1994 7