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State Req. i. Lennox Coal Seam and Overburden • These strata are dry in all areas of the permit and are not considered to be aquifers based on past drilling experience. However, these strata are important hydraulically because they cormrise the impermeable con- fining layers overlying the Wadge overburden aquifer. No observation wells currently monitor these strata. ii. Wadge Overburden Aquifer Two wells, GW-S21 and GW-S40-0, have been sompled to determine ground water quality in Wodge overburden strata. Of these two, only GW-S40-0 is considered to represent premining baseline water quality in this aquifer. One additional well, GW-541-~, monitors water level fluc- tuations and is not currently being sampled. Chemical data for these ground waters are given in Table 7-7. Basically, GW-540-~ yields a slightly mineralized Ca-Mg-HCO3 type water with a normal to slightly alkaline pH, high hardness and manga- nese, and low sulfate and fluoride concentrations. With the exception of manganese, this water is chemically suitable for domestic, livestock, and irrigation use based on the analyses presented in Table 7-7. It is, there- fore, considered to be a potentially significant aquifer with regard to its chemical quality. GW-S21 is located immediately downdip from a fly a~ disposol area just north of the mine permit boundary. Previous mining in this area removed only tfie Lennox coal seam, thus this well monitors leakage of potentially contaminated ground water into the Wadge overburden. This well was not drilled prior to mining or fly ash disposal activities, and therefore, baseline water quality data are not available for comparison. Ground water quality from GW-S21 is a slight to highly mineralized Ca-Mg-SO4 type water with normal to slightly alkaline pH, high hard- ness, manganese, and sulfate; and low fluoride concentrations. Using • GW-S40-0 for comparison, the Wadge overburden aquifer in this area may 7-22 Revised 5/27/81