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y s_ CONESTOGA-ROVERS &ASSOCIATES Sensitive Receptor Survey 1999: Cambria Environmental Technology, Inc. (Cambria) issued a Quarterly Monitoring Report — Third Quarter 1999 and Sensitive Receptor Survey for the subject site on November 2, 1999. Well records obtained from the California Department of Water Resources identified ten water wells within 2,000 feet of the site. The nearest well identified was a domestic well reportedly located at the Chevron site,just north of the site. This well was never located during field verification activities. The other nine wells were located over 700 feet away,north,northwest, and southwest of the site. The locations of identified wells are shown on Figure 1. Periodic Groundwater Extraction (GWE): Periodic groundwater extraction was performed at the subject between February 2000 and September 2003 to remove methyl tertiary butyl ether (MTBE)-impacted groundwater from beneath the site. Groundwater was extracted from wells MW-IA,MW-2A,and a UST complex backfill well (BF-1). Groundwater extracted during these events was transported via vacuum truck to the Martinez Refining Complex for recycling. Approximately 206,500 gallons of groundwater was extracted during this program. Calculations based on this volume and groundwater analytical data from the monitoring wells suggest approximately 5.45 pounds of TPH as gasoline (TPHg), 0.102 pounds of benzene, and 51.5 pounds of MTBE were recovered from beneath the site. Periodic GWE data is summarized in Table 4. Water Supply Well Destruction 2003: During August 2002, Cambria video-logged an abandoned water-supply well discovered at the subject site. It is unclear if this is the same well identified during the 1999 receptor survey, reportedly located at the Chevron site. The location of this well (RW) is shown on Figure 3. The well was constructed of six inch diameter steel well-casing and was screened from 107 to 115 fbg. Groundwater samples collected from the well during January 2003 did not contain any TPHg,BTEX, or fuel oxygenates. On February 14, 2003, with permission from San Joaquin County Environmental Health Department (SJCEHD), the former water supply well was properly destroyed. The destruction activities are documented in Cambria's April 29,2003 Well Destruction Report. Site Investigation 2003: One exploratory soil boring (CPT-1) was drilled during this investigation to assess the vertical extent of impacted soil and groundwater beneath the site. Soil sampling analytical results from boring CPT-1 indicate the vertical extent of gasoline and diesel constituents in the soil beneath the site is defined as no gasoline or diesel constituents were detected below 10 fbg. Grab groundwater samples were collected from various depth intervals from boring CPT-1. No TPHg, or BTEX was detected in grab groundwater samples collected. Up to 340 micrograms per liter (µg(L) TPHd and 81 gg/L MTBE were detected in the grab 0813 3 - Worldwide Engineering,Environmental.Construction,and IT Services