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GEOMATRIX <br /> Mr. Robert D. Mihalovich <br /> Chevron Environmental Management Company <br /> December 21, 2000 <br /> Page 3 <br /> as part of a Preliminary Endangerment Assessment performed at the adjacent Renown <br /> Property, however no data were available from these borings. Geomatrix advanced two soil <br /> borings (SB-1 and SB-2) in August 1996 to assess soil in the vicinity of two former pipelines <br /> near the southern portion of the property. Samples from the borings were analyzed for <br /> benzene, toluene, ethylbenzene, and total xylenes (BTEX) and polynuclear aromatic <br /> hydrocarbons (PAHs). <br /> Soil Conditions <br /> Based on existing data, the lateral and vertical extent of petroleum hydrocarbon-affected soil <br /> has not been defined on the site. A total of 23 soil samples collected from eight locations <br /> (shown on Figure 3) were analyzed for petroleum constituents. Fourteen samples were <br /> analyzed for TPHog; one sample was analyzed for TPHg, TPHd, and TPHk; nine samples <br /> were analyzed for PAHs; and six samples were analyzed for BTEX; results are summarized in <br /> Table 1. TPH at concentrations up to 8450 milligrams per kilogram (mg/kg) were detected in <br /> borings B-1 through B-3 and P-18 through P-20. BTEX was not detected in any of the <br /> samples analyzed from SB-1 and SB-2 and PAHs were only detected at low concentrations in <br /> sample SB-2-2.5 (0.25 mg/kg of benzo(a)anthracene and 0.16 mg/kg of pyrene). Sample <br /> locations are shown on Figure 2. <br /> Additional soil data are required to define the lateral and vertical extent of petroleum <br /> hydrocarbon-affected soil at the site. Additionally, data are required to assess the potential <br /> risk to human health posed by the affected soil. To date, only nine soil samples from three <br /> locations (SB-1, SB-2, and P-18 in the southern portion of the site) have been analyzed for <br /> PAHs, petroleum-related compounds that can potentially present a risk to human health. <br /> Groundwater Conditions <br /> No groundwater samples have been collected at the site and it is therefore unknown whether <br /> groundwater is affected by petroleum hydrocarbons at or above Regional Water Quality <br /> Control Board, Central Valley Region (RWQCB) water quality objectives (WQOs). Based on <br /> data collected at the adjacent Renown Property, groundwater at the site occurs at about 9 to 14 <br /> feet bgs and the horizontal hydraulic gradient is to the north-northeast. <br /> WORK PLAN TO ADDRESS DATA NEEDS <br /> Geomatrix will advance up to twelve soil borings (Figure 3) across the site to collect data to <br /> assess vertical and lateral extent of petroleum-affected soil, potential risks to human health, <br /> and potential impact to groundwater. Prior to drilling, Underground Service Alert (USA) will <br /> be notified, the soil boring locations will be cleared by a private underground utility locator, <br /> and appropriate permits will be obtained. The borings will be advanced using a hydraulically <br /> driven core barrel and drive sampler at each sampling location. One boring located in the <br />