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In addition to the monitoring done by the USGS, AmerAlia will install at least one alluvial monitoring <br /> well down-gradient from the project facilities in the Yellow Creek drainage. This well is anticipated <br /> to be located in the SW % of the NW '/4 of Section 21 where a gully that drains the project area <br /> intersects the Yellow Creek drainage. This monitoring well will be co-located with, or may be part <br /> of, an alluvial well field used to obtain water for the project. This alluvial well should intercept any <br /> near surface water draining the project area. <br /> G-5.2 GROUNDWATER <br /> As part of the experimental pilot plant operations, ground water will be monitored in three horizons: <br /> A-Groove, B-Groove and the lower portion of the lower aquifer near the Dissolution Surface. In the <br /> central part of the Piceance Creek Basin the generalized geohydrologic system has been divided <br /> into an upper and lower aquifer separated by a leaky semi-confining layer known as the upper part <br /> of the Mahogany Zone (Daub et. al., 1985). Water is generally artesian in these aquifers, but it <br /> does not typically reach the surface. The upper aquifer includes ground water in the lower part of <br /> the Uinta Formation, R-8 Zone and A-Groove. The upper part of the Mahogany Zone is a leaky <br /> semi-confining layer which generally separates the upper and lower aquifers. <br /> The lower aquifer extends from within the lower portion of the Mahogany Zone down to the top of <br /> the Saline Zone (Daub et. al., 1985). This interval is part of the Leached Zone. The B-Groove is a <br /> significant water bearing horizon located just below the base of the Mahogany Zone. The <br /> Dissolution Surface is coincident with the top of the Saline Zone below which sodium minerals have <br /> not been dissolved. The fact that salts have not been dissolved below the Dissolution Surface <br /> provides evidence that overlying ground water is confined by the Saline Zone. <br /> Two wells were completed in the mid 1970's by the USGS near and down gradient from the location <br /> of the Rock School project solution mining well field. One of these wells, termed USGS TH75-7A, <br /> was completed in the upper aquifer (A-Groove), and the other well, termed USGS TH75-7B, was <br /> completed in the lower aquifer (B-Groove). Water level measurements have been taken by the <br /> USGS and by the Colorado Division of Water Resources for most years since the wells were <br /> completed. There have been fluctuations in the water levels over the years, but the water level in <br /> the upper aquifer has stayed consistently higher than the water level in the lower aquifer as shown <br /> below: <br /> s <br /> G:IMM78545.00ZRedamation\Redamexh.DOC G-15 <br />