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CRAPTERFOUR Enuironmentai consequences <br />and precipitate nahcolite thus sealing potential migration pathways a short distance from the <br />mine cavity. <br />Leakage from the evaporation ponds at the Piceance Site could also result in degradation of the <br />' quality of water, particulazly in alluvial aquifers if present near the ponds. Although the ponds <br />will be lined, a liner failure could result in the migration ofelevated-TDS water from the surface <br />to alluvial aquifers. Quantification of this type of impact is not possible because flow rates and <br />fluid concentrations cannot be readily predicted, but the planned leak detection monitoring and <br />recovery/pump-back system would help minimize releases to groundwater. <br />' Other direct impacts are related to the degradation of water quality in the Lower Aquifer <br />(Pazachute Creek Member) from potential releases of production fluids. The Lower Aquifer has <br />TDS values that range from 600 mg/1 to 45,000 mg/1; therefore, the Lower Aquifer groundwater <br />' does have TDS concentrations within drinking water standards in areas of the Piceance Basin. <br />Data obtained from the White River Nahcolite (1997) operation (located approximately 2 miles <br />west of the proposed mine site) indicate that the water quality in the upper part of the Lower <br />Aquifer is 1,080 mg/I TDS. This indicates that the Lower Aquifer may have water quality that is <br />usable for stock watering or crop irrigation. However, data collected by American Soda in the <br />vicinity of the experimental mine site indicates that TDS values aze in excess of 60,000 mg/1 and <br />levels of fluoride and several other constituents aze above Colorado drinking water and irrigation <br />standards. <br />Releases of production fluids via casing leaks or mining cavity fluid excursions could elevate the <br />concentrations in either of these aquifers and be detrimental to the usefulness of either aquifer. A <br />release of the production fluid would not change the water type of either aquifer, since the fluid <br />has a similazcation-anion balance to the groundwater. These impacts would be the same for <br />both action alternatives. <br />The potential for impacts to Piceance Creek exists from the possible introduction of groundwater <br />with elevated TDS dischazging into the creek. Currently, the creek interacts with the aquifers <br />that underlie it by losing or gaining groundwater as it flows past the aquifers. Should the <br />differential head between the creek and the aquifers create a positive flow into the creek, water <br />that may have been impacted by operations would enter the creek. This could result in <br />groundwater with elevated TDS concentrations entering the creek. <br />Potential for indirect impacts to the groundwater quantity and quality may result from <br />subsidence. Subsidence in the Project Area could potentially fracture rocks both vertically and <br />' horizontally and result in increased hydraulic conductivity. Of significance is the potential <br />fracturing of the semi-confining Mahogany Zone, which sepazates the Upper and Lower <br />Aquifers. The increased hydraulic conductivity could potentially allow for the migration of <br />t higher TDS groundwater from the Lower to the Upper Aquifer or for migration of lower TDS <br />groundwater from the Upper Aquifer to the Lower Aquifer. The increased hydraulic <br />conductivity would result in an increase in the rate of recovery for groundwater pumped from <br />wells in the azea. <br />' Groundwater 4-15 <br />