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SUNDAY MINE COMPLEX-HYDROGEOLOGIC REPORT <br /> Groundwater in the Top Rim unit is present in the deeper workings of the SMC and is monitored in <br /> three monitoring wells installed at upgradient, intermediate, and downgradient locations relative to the <br /> SMC. Recharge to the Top Rim, or Salt Wash Member in general, is likely insignificant in the <br /> upgradient locations near the SMC adits as only minor outcrop occurs in this area. Recharge may be <br /> more prevalent in highlands several miles to the west,west of the Dolores River where Salt Wash <br /> outcrop is substantial and higher elevations at this location may have greater precipitation. The <br /> Dolores River may also be a recharge source where it is in contact or overlying the Salt Wash <br /> Member. Because the Salt Wash is confined by finer-grained strata, vertical recharge from over and <br /> underlying aquifers is considered minor. <br /> Discharge of the Top Rim unit likely occurs at exposed outcrop along Dolores River canyon mostly <br /> by way of evapotranspiration and springs and seeps. The unit is not tapped by area wells and is not <br /> being pumped. Some discharge may occur by way of leakage to over and underlying confining beds, <br /> especially where the Salt Wash is confined. <br /> Head elevation data indicate the potentiometric surface of the Top Rim is relatively flat in the SMC <br /> area;water level elevations at the Dolores River are approximately the same as observed at the <br /> mines.This is related to the underlying geologic structure(i.e.,the presence of the Disappointment <br /> Valley syncline). The mines of the SMC fall on the northeast limb of the syncline and the Dolores <br /> River is located on the opposing limb to the southwest. Any groundwater recharged to the Salt Wash <br /> will likely flow toward the synclines axis,which trends down the center of Disappointment Valley.This <br /> hydrogeologic condition, in addition to the low permeability of the Top Rim unit, suggests an almost <br /> stagnant flow regime where groundwater flow may oscillate between recharge and discharge at the <br /> Dolores River. In a case where flow may be to the Dolores River from the SMC area, indicated travel <br /> times would be measured in thousands of years. <br /> The occurrence of groundwater in the mine workings indicates that the Top Rim unit was basically <br /> unsaturated in the upper workings and only began to show saturated conditions in the deepest <br /> workings of the mines. Inflow in these areas is gradual and driven by the confined conditions of the <br /> aquitard at depth and the low pressure differential provided by the open workings. Mine inflow will <br /> continue until a"static" potential head is reached—this will likely be between 5,500 and 5,600 ft amsl. <br /> Groundwater chemistry data indicate an evolution of water chemical signatures in the downgradient <br /> direction; overall water quality decreases in this direction and water becomes more saline, a result of <br /> greater residence time. The exceedance of BSGWs in the downgradient areas is expected due to the <br /> natural concentration of dissolved mineral constituents with time. <br /> Western Water& Land, Inc. 55 <br />