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Table 2.1 Regional Hydrogeologic Characteristics Hydrogeologic Permeability Conductivity(k) Specific Porosity Material (k) cm2 cm/sec Storage(s2) m-1 (n) Sand 10-5- 10-9 10-1- 10-4 10-1- 10-1 25 - 50 Slit 10-8- 10-12 10-3_ 10-7 10-3- 10-4 35 - 50 Clay 10-12- 10-15 10-'- 10-10 10-2- 10-4 40- 70 (2) The Forward site is located in the San Joaquin hydrologic basin. Based on groundwater elevation contours published by the San Joaquin County Flood Control and Water Conservation District, the regional groundwater in the vicinity of the site was -20 to -30 feet NGVD (approximately 60 to 70 feet below ground surface (gbs)) and appeared to be flowing north-northeast in Spring, 1990. The sediments have been divided into three large groups based on gross lithology and pervasive distinctions in color. Although several strata can be recognized in the logs, for purposes of this report they were grouped into the following three larger groups: Group A Surface to approximately 28 to 40 feet-highly interbedded sandy silt, clayey silt, silt, and clay. A few layers of sand are present. Generally sands are fine grained. Most of the sediments have an oxidized appearance, showing an orange brown color. Group B Top - approximately 28 to 40 feet deep. Bottom - approximately 55 to 75 feet deep (25 to 35 feet thick)-interbedded sand, silty sand, silt, and clay. Sands are fine grained. Overall, this layer is a little sandier than group A. Sediments are distinctly less oxidized than group A; showing a grey brown color. Group C Top - approximately 55 to 75 feet deep. Bottom-to lowest available data (approximately 110 feet deep) -Sediments dominated by sand, fine to medium grained; some coarse grained or gravelly layers. A few layers of silt and clay material occur. Color is generally light brown to yellow brown. Grains are large enough to assess and conclude that the sediments appear to be granitic in origin. Surface Soils. The surface soils are mainly composed of two soil types typical of Victor Formation sediments. The two soils, as mapped by the Soil Conservation Service, are known as Clear Lake clay (CL) and Jacktone clay (ST). These soils are similar in composition; they were formed from alluvium. The most widespread soil type on the site is the Jacktone clay (ST), which covers the nearly flat terrain approximately 100 to 200 feet from the South Fork. Typically, this soil type is found on zero to 2 percent slopes forming a moderately deep hardpan of Forward Composting Facility Z:\PROJECTS\Allied Waste\Forward\Resource Recovery Facility\Permitting Services\2009 RCSI\RCSI Final 031609.doc; Page 26