1999-05-21_HYDROLOGY - M1999051 - Laserfiche WebLink

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mg/I (BLM, 1999). Higher TDS levels typically found downstream toward the White River are attributed to irrigation return water, ground water inflow from bedrock aquifers, and the concentrating effect of evaporation (Weeks and Welder, 1974). Water quality for alluvial wells near the Lease area was monitored in connection with a planned activity for the C-a Oil Shale Tract (BLM, 1985). Two wells of that monitoring program are close to the Lease area: GS-S24 (S24) in Corral Gulch near the southern boundary of the Lease area, and GS-S22 (S22) in Yellow Creek about 1.5 miles downstream of the area. Water quality mean concentrations for these wells from 1980 to 1983 are presented in Table G- 2. The mean concentration of sulfate for the alluvial wells exceeded the water quality standard for domestic supply of 250 mg/I, and the mean concentration for ammonia exceeded the standard for domestic supply of 0.5 mg/I in well GS-S24 for the monitoring period. These waters may be considered marginal for domestic use, but acceptable for agricultural uses. As stated above, the alluvial water quality in the drainage is protected only for agricultural use. G-2.2.2 Upper Aquifer The fractured oil shale of the Parachute Creek Member of the Green River Formation above the Mahogany Zone including the A-Groove, and the sandstone, siltstones, and fractured marlstone of the lower most part of the overlying Uinta Formation comprise the Upper Aquifer. Near the Lease area, the depth to the Parachute Creek Member is approximately 700 to 1,000 feet below surface. The Upper Aquifer ranges in thickness from 400 to 500 feet (Welder and Saulnier, 1978, and Hardy and Goodrich, June, 1996). Near the Rock School Lease, ground water flow in the Upper Aquifer is northeastward (BLM, 1985 and Robson and Saulnier, 1980). Ground water in the Upper Aquifer is classified as a sodium bicarbonate type with TDS values for the saturated portion of the Uinta Formation ranging from 550 to 1,060 mg/I in the central portion of the Piceance Basin (Robson and Saulnier 1980). TDS values measured.near the Project Area range from 651 to 1,110 mg/I (Tables G-2 and G-3). Water quality analyses from wells in the Upper Aquifer from previous studies near the Lease area are presented in Tables G-2 and G-3. In general, water in the Upper Aquifer near the Lease area is marginally suitable for use as a domestic water supply, but is acceptable for agriculture use and is considered an underground source of drinking water(USDW). G:tLMM78545.00Medamation%Redamexh.DOC G-8