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ll 1 t 1 1 C' Il ~J II II II II TECHNICAL MEMORANDUM AmerAlia, Inc. October 19, 1999 Page 3 and 1986a), and may provide important ground water baseline data for the proposed Project. Also analyzed were USGS data for surface water flows in the Yellow Creek drainage basin (Zook and Sares 1999 and USGS 1999). Five USGS surface water stations are in the vicinity or downstream of the Project area, only two aze currently active. A spring survey has been conducted and is summarized here. It should be noted that information from the proposed American Soda project has not been included in this analysis due to the controversial nature of the project (BLM 1998 and 1999a). Also, only selected wells from WRN were used in the analysis due to possible influence of mining operations on water qualiTy results (BLM, 19996). 2.0 GROUND WATER Ground water quality data from the C-a Tract, and the WRN, and two wells, installed by the USGS, within the Rock School Sodium Lease site were analyzed. This section describes and summarizes the available data from each of these projects, characterizes the general water type for each aquifer, and describes the presence or absence of seasonal trends in the data. 2.1 Description of Aquifers Alluvial sediments were deposited by water in the valleys of local drainages. The major drainage systems contain saturated alluvium and the minor drainages are generally dry. Thickness of alluvium in the area drainages range from several feet to about 100 feet in sections of Yellow Creek. The hydraulic gradient of the alluvial aquifer generally follows local topography. The bedrock zones are generally divided into the upper aquifer and lower aquifer. Early investigations by the USGS and studies on the C-a Oil Shale Tract defined the upper aquifer as water-bearing strata above the Mahogany zone of the Parachute Creek member of the Green River Formation including the Uinta Formation. The thickness of the upper aquifer is highly variable and ranges From about 300 to 700 feet. The lower aquifer was considered the water-bearing strata below the Mahogany zone in the Parachute Creek member of the Green River Formation. The bottom of the lower aquifer was defined as the bottom of the Parachute Creek member of the Green River Formation in the R-3 zone or Blue Marker at the contact with the underlying Garden Gulch member of the Green River Formation. Thickness of this unit is over 1,200 feet. The Mahogany zone is considered a leaky semi-confining layer, separating 2ndrinalTahnical Memo doc 10/19N9 TRC HYDRO-GEO CONSULTANTS