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Comoarison of Ground 4ater guality to Yater Use Standards. The Colorado Department of <br />• xeelth (CDOx) drafted basic standards for ground water, including stenderds for <br />agricultural use ((.e., irrigation and livestock), in 1986 <CDOx, 1986). These standards <br />have been summari xed and ere presented as Table 8 in Appendix A. Pa remeters denoted with <br />an asterisk on this table pertain to livestock standards; all other pa remeters pertain to <br />irrigation standards. Results of analyses performed on samples obtained from monitoring <br />wells during the 1994 water year have been compared to these standards, and the comparison <br />results are presented in Table 9 (Appendix A). <br />Table 9 shows that alluvial Yells 7A2, 19A, 21A, 23A, and USGS A8; overburden Yell 140V; <br />end coal Yells 14Y end 16Y all exceed the irrigation dissolved manganese standard of 0.2 <br />mg/l. This standard applies to crops grown in soils with pX values lower than 6.0. In <br />soils with a higher px (as is found in the agricultural soils surrounding Seneca II-Y <br />Mine), a more realistic standard would be 10 mg/l (EPA, 1976). <br />The irrigation dissolved iron stenderd of 5.0 mg/l was exceeded at alluvial Yell 7A2, coal <br />Yell 144, and overburden Yell 140V. 4e[er with this iron concentration will precipitate <br />iron oxides on the leaves when the crop is spray-irrigated, but chould not be a problem <br />• for flood irrigation (EPA, 1976). <br />Fluoride values et overburden Yells 150V end 180V and coal Yell 15Y exceed the standard of <br />2 mg/l. Nigh fluoride values have also been noted at the Seneca if Mine in certain wells <br />with a high percentage of sodium (as is slso the ease with all three walla). This <br />observation apparently reflects neturel conditions. <br />At the Seneca II-Y shop well (Yell 201TC), CDOH drinking water stenderds were used to <br />determine its suitability. The secondary stenderd for iron (0.3 mg/l) was exceeded with <br />values of 6.86 (November, 1993) and 2.13 mg/l (August, 1994). The secondary standard for <br />manganese (0.05 mg/t) was exceeded with values of 0.23 (November, 1993), 0.11 (June, <br />1994), end 0.12 mg/l (August, 1994). xowever, bottled water is consumed at Seneca 11-Y. <br />Also, since the aquifer for the shop well (Trout Creek Sandstone) starts et 280 feet below <br />the Yedge Coel and is separated by confining shale layers, water from this well should not <br />be affected by mining and, therefore, reflects the neturel chsraeteristies of the aquifer. <br />Tab 7 of the Seneee II•Y PAP eonteins a section that discusses Che suitability of using <br />• water from the veri ous aquifers monitored at the Seneca II-Y Mine for irrigation or <br />7 <br />