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Appendix B:Previous Environmental Investigations (dibenz[a,h]anthracene at 0.0064 µg/L) detected in a sample from SB-2. Total Dissolved Solids (TDS) concentrations ranged from 2,260 to 2,560 milligrams per liter(mg/L),which did not exceed the TDS WQO of 3,000 mg/L. Based on the results of the investigation, SAIC recommended additional step-out borings to delineate the extent of affected soil and groundwater SAIC 2009 SOIL AND GROUNDWATER INVESTIGATION From November 9 through November 18, 2009, SAIC advanced 15 borings (SB-30 through SB- 44)using a Geoprobe° 7822DT direct-push rig. Borings were advanced to total depths between 25 to 35 feet bgs. Hydrocarbon-affected soil was encountered in SB-30, SB-32, SB-36, and SB- 39 through SB-43. TPHc were detected above ESLs in 2 soil borings. The highest concentration was detected in boring SB-39 at 20 feet bgs (6,900 mg/kg). Ethylbenzene, was detected above the RSLs in one soil borings at a concentration of 0.051 mg/kg in SB-39 at 20 feet bgs. PAHs were detected in soil samples from 5 borings with a maximum concentration(2-methylnaphthalene at 4.5 mg/kg) detected in SB-39 at 20 feet bgs. Groundwater samples were collected from 7 borings by SAIC. TPHd was not detected above ESLs in any of the groundwater samples submitted for analysis. BTEX constituents were not detected above ESLs or WQOs in any samples. PAHs were detected in groundwater samples from four borings with a maximum (acenaphthene at 0.048 µg/L)was from a sample collected from SB-38. In a sample collected from SB-41, TDS was detected at 2,190 mg/L, which did not exceed the WQO of 3,000 mg/L. Additionally, a water sample was collected from the nearby Foster Well, which is currently in use by a nearby residence. The Foster Well is located up gradient of the previously advanced boring SB-19. The Foster Well sample (FosterWell-1) did not contain concentrations of TPHd, BTEX, or PAHs exceeding the laboratory reporting limits, WQOs, or ESLs. Various water- quality parameter analytical results from the Foster Well, such as General Minerals and TDS, exceeded screening levels. Based on past experience at HPP-BTR project sites, attenuation of crude-oil constituents in groundwater occurs a very short distance from HPP-BTR facilities, and it is improbable that affected groundwater extends from the site as far as the Foster Well. In addition, the up-gradient position of the Foster Well in relation to the areas of known affected groundwater suggests that it is unlikely it will be affected by crude oil related to the former OVP or TAOC pipelines. SAIC evaluated the results of the investigations and concluded the following regarding the nature and extent of affected soil and groundwater at the site: • Field observations and laboratory analytical results indicate that there are two areas of affected soil and groundwater which have been delineated. • The extent of affected groundwater is stable or decreasing, and concentrations of dissolved constituents will gradually decrease as the petroleum hydrocarbon mass is depleted. The lack of BTEX in groundwater samples indicates that intrinsic biodegradation has been, and continues to be, active at this site. 3. SAIC,2010. Soil and Groundwater Investigation Report—Mountain House Development Site#6. February. B-2WAra am mmmFJ"f1%imw® Plum Science to Solutions