SITE INFORMATION AND CORRESPONDENCE

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ARCADIS Ms. Kristi Shelton November 12,2009 (EDR). A totabof three water wells were identified by EDR that are located within a one mile radius of the Site. A copy of the EDR report is included as Attachment B. In addition, well searches were previously submitted in April 1991 and November 1996. The searches identified wells located within a one-half mile radius of the Site. The results of these previous well searches are included as Attachment C. 3. Provide cross-sections showing the Site lithology. ARCADIS has attached a total of five cross-sections that were previously submitted for investigations performed at the Site. Copies,of these cross- sections are included as Attachment D. In addition to the above requests, the Regional Board also provided comments regarding soil contamination at the Site. In October 1995, a total of 17 direct-push soil borings (S1 through S17)were advanced in or around the area of the April 1987 pipeline, release (see Figure 2). Twelve soil samples were submitted for laboratory analysis of total petroleum hydrocarbons as gasoline (TPHg); and benzene, toluene, ethylbenzene, and •total xylene (BTEX) based on field screening with a photoionization detector (PID). Results of the investigation indicated a maximum TPHg concentration of 1,500 milligrams per kilogram (mg/kg). Analytical results also indicated maximum benzene, toluene, ethylbenzene, and total xylene concentrations of 5.6 mg/kg, 75 mg/kg, 57 mg/kg, and 390 mg/kg, respectively. All of these concentrations were detected in a soil sample collected from soil boring S8 at a depth of 9 feet bgs. Soil boring S8 was advanced in Grant Line Road, within the area of the former spill. A sample collected from the same boring at a depth of 12 feet bgs indicated similar concentrations. Analytical results from the soil investigation are presented in Table 2. According to the Regional Board, the Gross Contamination Ceiling Levels for shallow soil (commercial/industrial land use) where groundwater is a current or potential source of drinking water are as follow: TPH (500 mg/kg), benzene (870 mg/kg), toluene (650 mg/kg), ethylbenzene (400 mg/kg), and.xylenes (420 mg/kg). Only the TPHg concentrations (1,500 and 1,400 mg/kg) detected in the soil samples collected from boring S8 (S8-9' and S8-12', respectively) exceeded the Gross Contamination Ceiling Level of 500 mg/kg for TPH. Based on the results of the investigation, soil contamination exceeding Gross Contamination Ceiling Levels is limited to the area immediately adjacent to soil boring S8. ARCADIS does not feel the concentrations detected in soil boring S8 warrant additional assessment based on the location of the contamination (beneath Grant Line Road), the limited extent of the contamination, and the likely decrease in concentrations since the investigation was performed in October 1995. . - I Page: G:ICooe %ALLEMChevron OM ACm l HDnoMCbeure Report AddmMumlGlowm Report Addendum_11.12.09.d. 2/5 li