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<br />CHAPTERTHREE Affected Environment <br />gravel along the floodplains and alluvial fans in the lazger valleys. The floodplain deposits are , <br />mostly gray, brown, and buff silts and sands. The alluvia] fan deposits consist of angular <br />sandstone and mazlstone boulders and pebbles mixed with silts and sands derived from nearby <br />hilly terrain. The alluvium is less than 50 feet thick (Duncan 1976a and 1976b) , <br />The stratigraphy underlying the Piceance Site is the same as that detailed in Section 3.1.1.3 for <br />regional geology. Asite-specific stratigraphic section for the Piceance Site is presented in <br />Figure 3.1-4. ' <br />It should be noted that the highest concentration of halite in the Saline Zone of the Parachute <br />Creek Member is found toward the center of the Piceance Creek Basin. The Piceance Site is ' <br />located in the dawsonite-nahcolite zone and on the edge of the area containing halite (Figure <br />3.1-1). Based on monitoring well 20-1 at the Piceance Site, the depth to the top of the Saline <br />Zone is about 1,400 feet bgs. This interval is approximately 800 feet thick. The depth to'the ' <br />Love Bed at we1120-1 is approximately 1,700 feet bgs. <br />3.1.2.2 Pipeline Corridor , <br />The majority of the pipeline corridor would lie on the Uinta Formation, which is described in <br />3.1.1.3, above. At the two locations where the pipeline crosses Piceance Creek, 'the primary ' <br />geologic unit is recent alluvium, which includes the Piney Creek alluvium and y~~unger deposits. <br />At Davis Point, the pipeline crosses the Parachute Creek Member of the Green River Formation <br />and, at the base of Davis Point, lower parts of the Green River Fortation (Tweto 1979). <br />3.1.2.3 Parachute Site , <br />The Parachute Site lies on the southern end of the Piceance Creek Basin, as described in <br />Section 2.1. In the area surrounding the Parachute Site, more than 20,000 feet of sedimentary <br />rocks ranging in age from Cambrian to Tertiary overlie the basement crystalline rocks (COE , <br />1985). The floor of the Parachute Creek valley is lined with relatively thick deposits of <br />unconsolidated soils. These soils were deposited primarily in extensive alluvial fans created by <br /> <br />deposition of poorly sorted soil and rock materials carried down tributaries toward Parachute , <br />Creek from the canyon slopes during periods of high runoff (COE 1985). <br /> , <br />3.1.3 Geological Resources <br />3.1.3.1 Oil and Gas , <br />Oil and gas deposits are found throughout the Project Area. The area is considered to be <br />valuable for oil and gas. Coal bed methane reserves in the Piceance Creek Basin approach , <br />84,000 million cubic feet (MMCF). Through January 1990, a total of 204,410 ba-rels of oil and <br />235,865,770 MCF of natural gas have been produced within the Piceance Creek E{asin. Gas <br />production from the Piceance Creek Basin is generally from small subpazallel northwest trending <br />folds, the most prominent of which is the Piceance Creek anticline. <br />The federal government has leased 100 percent of the oil and gas mineral estate widerlying , <br />American Soda's soditrrn lease tracts (T1S R97W Sections ]5, 16, 17, 18, 19, 20, :21, 22, 28, 29) <br />3-6 Geology ' <br />