SITE INFORMATION AND CORRESPONDENCE

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Former Union Oil Bulk Plant, Tracy• - 3 - • 2 August 2011 Figure 2 shows the location of the groundwater monitoring wells and Tables 5 and 6 present the historical groundwater analytical data. On 23 March 2007, ConocoPhillips sampled the domestic well at 8197 West 11th Street (domestic well). ConocoPhillips collected the sample from the water hose connected to the hose bib after the water was purged for two minutes. The sample contained TPHd at 140 pg/L, but the laboratory flagged the result because the laboratory control sample surrogate recovery was not within laboratory established control limits and the laboratory method blank contained TPHd. On 4 April 2007, ConocoPhillips resampled the domestic well. This water sample was collected from the tap after the hose had been disconnected, the tap sterilized with a match, and the water purged for five minutes. The sample contained TPHd at 110 pg/L, but the laboratory flagged the result because the laboratory control sample surrogate recovery was not within the laboratory established control limits and the method blank contained TPHd. On 16 April and 27 April 2007, ConocoPhillips resampled the domestic well and sent the samples to another laboratory. These water samples were collected from the tap after the water was purged for 30 minutes to allow evacuation of the holding tank between the well and the tap. Neither of these samples contained petroleum hydrocarbons. SOIL VAPOR INVESTIGATIONS In June 2009, ConocoPhillips installed and sampled five soil gas sample probes. All five locations contained TPHg above the ESL for residential receptors. In November, ConocoPhillips installed additional soil gas probes next to the previous locations. Only the sample south of the former loading rack, SG-8, contained concentrations above the residential ESLs. In June 2010, ConocoPhillips installed a third soil gas sample probe near SG-3 and collected a soil vapor sample. TPHg was detected at a concentration of 100,000 micrograms per cubic meter (Ng/m). In November, ConocoPhillips excavated the contaminated soil around SG-3. No other petroleum hydrocarbons were detected above the residential ESLs. In February 2011, ConocoPhillips installed a temporary soil gas probe in the location of the excavation of the contaminated soil and collected a soil vapor sample. The soil vapor sample did not contain TPHg above the laboratory detection limit. Table 7 presents the historical soil gas analytical data. SENSITIVE RECEPTORS In 2005, ConocoPhillips performed a sensitive receptor survey to locate private wells or other receptors within 1,000 feet of the Site. One domestic water supply well is onsite. The well is 1,136 feet deep and used for non-potable sanitation purposes. No petroleum hydrocarbons have been detected in this well. Two other nearby domestic wells were identified at 8197 East 11th Street (130 feet southeast of the Site) and 8188 East 11th Street (370 feet south- southeast of the Site).