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State Req. <br />Observation well GW-S 17 monitors ground water down gradient of the • <br />mine operation in the vicinity of the Wadge Impoundment. This well <br />provides a highly mineralized Na-SO4 type wafer with alkaline pH, high <br />hardness and sulfate, and low fluoride. Trace element concentrations are <br />well below federal and state wafer quality standards for drinking water <br />and irrigation use. However, elevated levels of total dissolved solids, <br />sulfate, and SAR will limit its use to livestock only. The chemical <br />quality of this ground water results from mixing between Na-HCO3 type <br />ground water and Ca-Mg-SO4 type surface water recharge from the <br />Wadge Impoundment. <br />iv. Wolf Creek Overburden <br />Six wells, GW-56, GW-S7, GW-S8, GW-SII, GW-536-0, and GW-537-~, <br />monitor Wolf Creek overburden strata in the mine plan area. Water <br />quality was monitored for wells GW-S6, GW-S8, and GW-SII. Complete <br />chemical analyses overburden strata typically yield a slightly mineralized <br />Na-HCO3 type water with alkaline pH, low hardness, and high SAR and <br />fluoride concentrations. Higher than normal fluoride concentrations (4.1 <br />maximum) found in these ground waters may be attributable to low <br />calcium concentrations (Hem, 1970). All trace element concentrations <br />are below water quality standards with the exeption of mercury. This <br />element was detected in two wells, GW-58 (0.11 ug/I) and GW-56 <br />(0.34 ug/I), on a one time basis that exceed the 0.05 ug/I water quality <br />standard . in Colorado. Laboratory error is suspected in both samples <br />because other samples from the same wells indicate a low mercury <br />concentration. In the case of GW-58 (8-I I-79), a mercury concentration <br />of 0.0 ug/I is reported from a split sample obtained by the U.S. <br />Geological Survey. <br />From a water quality standpoint, Wolf Creek overburden is considered to <br />be marginally significant for domestic and livestock use. Locally high <br />fluoride concentrations from this water may cause dental fluorosis <br />(mottling of the teeth), especially in children (Fetter, 1980). High SAR <br />values make this water unsuitable for irrigation. <br />7-28 <br />Revised 5/27/81 <br />