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<br /> Phase I Environmental Site Assessment
<br /> g City of Stockton Multi-Modal Station/Shopping Center
<br /> Page 14
<br /> 1 601 E Miner Avenue, Stockton,CA
<br /> Fourth Quarter 2000 Monitoring Report, dated January 31, 2001
<br /> Groundwater monitoring activities took place on November 6, 2000 Samples were collected from MW-I
<br /> through MW-5, MW-7, GWX-1, and VX-1 The top of the well screens of monitor wells MW-1, MW-2,
<br /> and MW-3 were 10 to 35 feet below the groundwater surface TPH-G was detected in the groundwater
<br /> samples from MW-1, MW-2, MW-3, VX-1, and GWX-1 at concentrations of 14,000, 17,000, 360,
<br /> i 23,000, and 100,000 gg/L, respectively Concentrations of benzene ranged from 580 to 23,000 gg/L in
<br /> MW-1, MW-2, 13WX-1 and VX-1 MTBE was detected at concentrations of 2 7 to 720 µg/L in the
<br /> samples from MW-1, MW-2, MW-3, GWX-1, and VX-1 Several other petroleum-based volatile organic
<br /> compounds were detected in the samples from MW-1, MW-2, MW-7, VX-1, and GWX-1 Based on
<br /> j these results, it appears that the groundwater most impacted is in the vicinity of the former USTs The
<br /> groundwater gradient for the site is to the northeast IT Corporation recommended the continuation of
<br /> quarterly monitoring along with the possible initiation of an soil vapor extraction (SVE) or air sparging
<br /> system
<br /> Former Valley Volkswagen
<br /> 647 E. Miner Avenue, Stockton,CA
<br /> Work Plan for Additional Monitoring Well Installation, dated March 5, 2001
<br /> On July 29, 1987, two waste oil USTs were removed from the site The two soil samples collected
<br /> indicated the presence of TPH-G and total xylenes at 12 and 14 feet below ground surface (bgs) Two
<br /> additional soil samples were collected from the pit at a depth of 16 5 feet bgs on September 1, 1987 One
<br /> of the samples was not analyzed, while the other sample indicated the presence of TPH-G at a
<br /> concentration of 2,000 gg/kg On September 25, 1987, twelve samples were collected from the soil
<br /> stockpile Four samples indicated the presence of TPH-G The stockpile soil was used to backfill the
<br /> • excavation pit in October 1987
<br /> t In May 1995, three soil borings were advanced to 46 feet bgs and monitor well MW-1 was installed to
<br /> 62 5 feet bgs The soil boring samples did not indicate the presence of TPH-G, BTEX constituents, or Oil
<br /> and Grease, except for the sample from SB 1 at a depth of 25 5 feet bgs, which indicated total xylenes at a
<br /> concentration of 0 010 mg/kg Soil samples from the MW-i boring indicated the presence of TPH-G at
<br /> depths of 20 5 and 30 5 feet bgs Initially, the groundwater samples from MWA indicated low to
<br /> moderate levels of TPH--G and BTEX Subsequent samples detected only low levels of MTBE
<br /> l In July and November 1999, four soil borings were advanced No analytes of interest were detected in the
<br /> soil samples, but TPH-G and benzene were detected in the groundwater sample of HPI During the most
<br /> recent groundwater monitoring event, only MTBE was detected at 22 gg/L
<br /> The work plan proposes the installation of one new monitor well, down-gradient of MW-1, to a depth of
<br /> 50 feet bgs and screened from 25 to 50 feet bgs Soil samples will be collected at five-foot intervals The
<br /> purpose of this work is to determine if an MTBE plume is present on site and document its possible extent
<br /> and magnitude of the plume
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<br /> t� CONDOR
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