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from both the Salt Wash (if present) and Entrada Formations would eventually reach the <br />axis of the syncline and then migrate to the southeast following the plunging syncline. It <br />is unlikely that groundwater from these formations would ever discharge to the surface <br />environment. <br />Several of the geologic units in the area exhibit low permeability values and restrict the <br />downward movement of water from surface recharge to underlying aquifers. UMETCO <br />(1997) conducted a series of packer tests in the Summerville Formation to measure the <br />hydraulic conductivity for work involving the Uravan Mill and the associated waste <br />disposal facility located on Club Mesa. These tests, conducted at 167 to 270 psi, did not <br />introduce any water into the formation indicating that the hydraulic conductivity of the <br />Summerville Formation is no greater than 1.0 E -08 cm/s. This conclusion is supported <br />by laboratory testing that measured horizontal and vertical permeabilities of less than 9.7 <br />E -10 cm/s. For all practical purposes, this low permeability value indicates that the <br />Summerville Formation is an aquiclude - rock incapable of transmitting groundwater. <br />Peel Environmental Services (1993) conducted hydraulic tests of the Kayenta Formation <br />using packer tests that showed the formation did not take water at a pressure of 745 psi. <br />Based on these tests, the report estimated that the permeability of the portions of Kayenta <br />Formation is 3.8E -08 cm/s - basically impermeable. The test interval was in a shale unit <br />of the Kayenta Formation and is not representative of the entire formation. However, the <br />lowest permeability unit controls flow for the entire formation. <br />For mining to impact the regional groundwater system, mobilized constituents would <br />have to migrate from the upper sandstone unit of the Salt Wash Member through the <br />lower sandstones and bentonitic shales of the lower portion of the Salt Wash and through <br />the impermeable Summerville Formation to reach the Entrada Formation. <br />8.3.4 Recharge <br />As noted in Section 8.3.1, the Burro Canyon Formation forms the highlands above the <br />mine site and the exposed bedrock across the surface provides significantly more area for <br />recharge compared to the canyon walls for the lower stratigraphic units. While <br />groundwater may occur in the springs at the Burro Canyon/Brushy Basin contact, as <br />indicated by a spring on the west side of the river, there are no mapped springs in <br />highland immediately to the east that would indicate substantial quantities of <br />groundwater exist in the area near the mine. <br />The Entrada Formation is the uppermost bedrock unit in the Dolores River Valley at <br />Slick Rock based on the geologic map for the area (Cater, 1955). Seepage from the river <br />and the saturated alluvium provides substantial quantities of water to recharge the <br />underlying sandstones. Well yields in the area of 50 gallons per minute indicate that the <br />Entrada Formation is an important water resource in the area - principally due to the large <br />amount of available recharge. West of the river, the bedrock dips steeply to the northeast <br />off the flanks of the Dolores River /Lisbon Valley anticline. The Entrada and Navajo <br />Formations are exposed along the canyons that dissect the landscape west of the river. <br />O'Connor Design Group Inc. T - 13 <br />