SITE INFORMATION AND CORRESPONDENCE

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Mr. Jerry Lile October 2, 2001 Page 2 and Bruya, Inc. of Seattle Washington, a California-certified laboratory analyzed soil and grab groundwater samples for petroleum-related hydrocarbons. Forensic evaluation of the soil samples indicated that the petroleum hydrocarbons present in the soil likely represent degraded crude oil. Document Reviewed HERD reviewed 'Report of Additional Soil and Groundwater Investigation and results of the Up- dated Human Health Screening Evaluation, Ridgeway(former Burns] Property (APN 232-170-05), Tracy, California". This document, dated July 20, 2001, was prepared by Geomatrix Consultants, 2101 Webster Street, 12'h Floor, Oakland, California 94612, contractors to Chevron Environmental Management Company. Scope of Review The 'Report of Additional Soil and Groundwater Investigation and Results of the Updated Human Health Screening Evaluation, Ridgeway (former Bums] Property (APN 232-170-05), Tracy, Califor- nia"was reviewed for scientific content and sufficiency to support a risk-based clean closure of the site under the Voluntary Cleanup Program. Sampling details, analytical methodology, and technical approach were evaluated. General Comments A total of 10 soil samples and 4 grab groundwater sample were taken to define the vertical and horizontal extent of petroleum hydrocarbon affected soil and groundwater. Soil sample depth began at 8.5 feet bgs and advanced downward to 13- to 19 feet bgs. Surface soils were not affected and, presumably, the former pipeline was located approximately 5 feet below grade. The extent of petroleum hydrocarbon contamination in the soils and groundwater adjacent to the former pipeline right-of-way is limited vertically and horizontally. Levels of petroleum-related hydrocarbons ranged from ND to 14,000 mg/kg for TPH crude and from ND to 5,600 mg/kg for TPH diesel in soils. The PAHs acenaphthene, fluorene, and phenanthrene were detected in shallow groundwater at 0.1, 0.3, and 0.2 µg/L respectively. BTEX constituents were less than the detection level in soils. Low levels of PAHs (commonly associated with crude oils, fuel oils, and diesel) were detected up to 6.8 mg/kg for naphthalene, up to 5.7 mg/kg for phenanthrene, and up to 3.7 mg/kg for fluorene. Two PAHs, benz(a)anthrancene and chrysene (more notably associated with crude oil) were the only PAHs detected at the site that were potential carcino- gens (0.13 and 1.0 mg/kg respectively). None of the constituents identified above were from surface soil samples. Based on the levels of petroleum-related constituents identified at the site, the soils were not completed saturated with product and the product was only identified in the depth profile of from 8.5 to 11 feet bgs. The constituents of concern identified on the property included eight PAHs (acenaphthene, benz(a)anthracene, chrysene, fluoranthene, fluorene, naphthalene, phenanthrene, and pyrene) and and the volatile organics toluene and xylene 0.7 and 1.5 ug/L. The maximum concentra- tions of these constituents were used as source terms to estimate chronic daily and jifetime doses of constituents for estimating potential excess cancer risk and noncancer threshold ef- fects.