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• Although the commonly exceeded domestic drinking water standards are considered secondary by the CDOH (CDOH, 1994), the comparisons show that all geologic units monitored in the Yoast mining area ere unsuitable for domestic use. Ground water from Yoest monitoring wells would require substantial treatment and intensive monitoring according to regulations prescribed for public water supplies before the water could be used for domestic drinking water purposes. Agricultural Meter Suitability. Table 7-21 presents apritulturel (irrigation) standards developed by the CDON and other agencies for ground water. The agricultural standardc were compared against sample constituent concentrations meecured in each Coast monitoring well. Table 7-22 presentc the results of the comparisons in a format identical to Table 7-20. The comparison results presented in Table 7-22 show that the manganese agricultural ground water standard is commonly exceeded in the Annand Drew and Grassy Creek alluvium, end et Sege Creek alluvial Yell YSALB. Yith the exception of the Yolf Creek coal seem, manganese in all other units monitored at the Yoest mining area has been measured in excess of the • egriculturel standard. Both the sulfate end TDS standards were commonly exceeded in all units. The iron standard has been commonly exceeded in three of the four Grassy Creek alluvial wells, end occasionally in Yadge overburden well YOV1. The pH standard was exceeded et least once Cgreater then 8.5 S.U.) in all alluvium monitored, Yadge coal seam, Madge overburden, end wedge underburden. The cadmium agricultural standard was only exceeded once in the Yadge overburden (YOV28) end the Madge underburden (YYU28). The only exceedence of the arsenic standard was observed et Yadge coal YeLI YY2 (250 ug/l); however, this first measurement for arsenic is considered suspect es subsequent analyses have not yielded detectable tontentrations. Based on the comparisons, ground water in the alluvium monitored along Annand Drew, Grassy, end Sege Creeks is unsuitable for egriculturel use. Yith the exception of the Wolf Creek coal seem, occasional exceedences of manganese and pN et select bedrock wells suggest that ground water quality in these bedrock units may also be unsuitable for egriculturel purposes. Another method of assessing the suitability of ground water for irrigation is to use • sodium-salinity hazard diagrams, where specific conducta nce is plotted against sodium-adsorption ratio (U.S. Salinity Laboratory, 1954). Figure 7-1 presents a sodium-salinity hazard diagram constructed with mean values for specific conductance (EC) 63 Revised 03/01/95