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' (conglomerates) to fine-grained (sandy siltstones) sedimentary strata, obscured by undifferentiated coarse to fine-grained detrital deposits at the foot of the ridge, are ' present at higher elevations in the area of the site. Permanent bodies of surface water are not located within '/2-mile of the site. Grazing of livestock (cattle) occurs north and east of the site. On 16 November 1999 DTSC approved the RFI Workplan dated 9 August 1999. In December 1999, the RFI Field Investigation Workplan was implemented. At SWMU ' #21, 15 soil samples were collected at seven (7) locations. The analytical results for the surface samples for chromium and lead were significantly below the PRGs and therefore, no further sampling or analysis for these metals was required by DTSC. Also, ' PCB analysis results, identified as Aroclor 1254, were below the PRG for Aroclor 1254, and subsequently no further sampling or analysis was required for PCBs. Hydrocarbon concentrations exceeding 100 mg/kg (either TPHd or O&G) were detected at each of the seven sampling locations at SWMU 21, with concentrations at the 6 to-12 inch bgs sample locations ranging from 110- mg/kg to 7,100-mg/kg. Based on this finding, this CMS Workplan addressed additional sampling and analysis to further assess the horizontal and vertical extent of hydrocarbon impact in the soil. 1 On 25 May 2001 seven (7) "direct push" borings were advanced at the site to collect soil samples for visual assessment of soil characteristics and for chemical analysis. The borings were continuously cored to a total depth of 15-feet bgs. Soil samples from 2.5- feet (ft) bgs and 5.0-ft bgs were collected from each boring and forwarded for laboratory analysis of TPHd and O&G. Analytical results indicated TPHd and O&G impact to soil ' as deep as 12.5-ft bgs in some borings. Based on the soil analytical results indicating the presence of impacted soil in a semi-circular area proximal to the oil AGST, further delineation of soil impact was performed using grab soil samples from "pot holes" and testing for petroleum hydrocarbons using an optical opacity field-testing kit. Due to the proximity of the hydrocarbon impacted soil to the base of the AGST five (5) piers were installed around the AGST to protect the integrity of the AGTS during excavation activities. Approximately 1,200-tons of hydrocarbon impacted soil was excavated from the area around the AGST and transported as California non-hazardous regulated waste manifests for disposal at the Forward Landfill. Analytical results for soil collected from the excavation sidewall and floor indicated the presence of two (2) limited areas in the excavation with hydrocarbons exceeding cleanup levels at approximately 15 to 17-ft bgs. ' The results of the CMS were presented in the "Corrective Measures Study, Preliminary Field Activities & Results Report" prepared by CE in August 2001 that was submitted to ' the DTSC. On 29 April 2002 the DTSC approved Corrective Measures Study Follow Up was implemented. The site activities included drilling two (2) 8" diameter borings, and nine (9) direct push 1.5" diameter borings installed radially around the eastern side of SWMU #21. Soil samples were collected and analyzed for lithological description and CE Project No.99R-4041 Additional Investigation Work Plan 2