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removed from the site. The native soil layer beneath the drilling mud was visually <br /> examined and found to be clean and not discolored. After waste removal was <br /> completed, the site was regraded. <br /> The cleanup limits for the native soils underlying the surface impoundments were <br /> 200 mg/kg chloride, 5 mg/kg barium, and 250 mg/kg sulfate. Analysis of <br /> confirmation soil sampling indicated that all of the constituents of concern (COCs) - <br /> barium, chloride, sulfate and electrical conductance (EC) - were at levels below the <br /> approved site cleanup levels. <br /> PG&E submitted a"Surface Impoundment Closure-Closure Certification Report" <br /> December 5, 1994. Corrective action measures that have been taken at the site in <br /> accordance with the former Title 23 CCR, Chapter 15, Section 2550.10(c) include (1) <br /> the elimination of the brine and drilling mud discharge in 1986, (2) the removal of the <br /> remaining drilling muds in 1994, and (3) the placement of an engineered soil cover to <br /> control drainage and percolation into the site in 1994. <br /> 3.0 GEOLOGIC DESCRIPTION <br /> 3.1 Groundwater Hydrogeology <br /> The most comprehensive evaluation of groundwater beneath the site is presented in <br /> the 1990 SWAT report (PG&E; June 29, 1990). This report contains an analysis of <br /> the site hydrogeology and geologic cross sections incorporating information from 31 <br /> borings, two piezometers, nine monitoring wells, and a number of well points. The <br /> Z:111ROP•PRn 1999k 1524.pWeliv WIPI•1524•I.d. <br /> 4 <br />