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. Ms Victoria McCartney
<br /> March 24, 2005
<br /> Page 4
<br /> lake was located in a residential area approximately 1,500 feet southwest of the site Well
<br /> logs obtained through the State of California, Department of Water Resources (DWR)
<br /> Indicated the presence of an Irrigation well owned by the California Department of
<br /> Transportation (Cal-Trans), which was screened from approximately 214 feet to 350 feet
<br /> bgs, and located approximately 315 feet west of the site (Cambria, 1999) According to
<br /> Cambria, the Cal-Trans well had been destroyed in preparation for reconfiguration of the
<br /> Interstate 5 and Hammer Lane Interchange (Cambria, 2000) According to Mr Witzak Gilon x
<br /> of the City of Stockton Municipal Water System (CSMWS), there were no CSMWS water
<br /> supply wells located within the 2,000-foot search radius (Cambria, 1999)
<br /> On June 12 and 13, 2000, Cambria replaced destroyed Well MW-1 and damaged Well MW-
<br /> 2 with wells MW-1 R and MW-2R, which were completed at depths of 31 5 and 30 feet bgs,
<br /> respectively In addition, Cambria drilled and installed two additional groundwater
<br /> monitoring wells (MW-9 and MW-10) to total depths of 31 5 feet bgs Laboratory analysis of
<br /> soil samples collected from the soil borings Indicated maximum concentrations of TPHg at
<br /> 0 82 mg/kg (MW8-12') and MtBE at 2 6 mg/kg (MW8-30) BTEX was not detected above
<br /> laboratory detection limits Laboratory analysis of groundwater samples collected from the
<br /> wells confirmed maximum concentrations of TPHg at 3,400 µg/L (VW-1), benzene at 84
<br /> pg/L (VW-1), MtBE at 250,000 µg/L, and tert-butyl alcohol (TBA) at 17,000 84 µg/L (MW- y
<br /> 2R, Cambria, 2000)
<br /> In August 2000, GR implemented an Interim migration control plan at the site to reduce the
<br /> amount of petroleum hydrocarbons and MtBE beneath the site, and to prevent further off-
<br /> site migration of the dissolved plume (GR, 2000) The plan consisted of the periodic
<br /> extraction of approximately 5,000 gallons of groundwater from wells historically containing
<br /> the highest concentrations of petroleum hydrocarbons and MtBE (MW-1 R, MW-2R, and
<br /> VW-1) Groundwater batch extraction activities continued through June 2004, resulting 1n
<br /> the removal of approximately 958,180 gallons of groundwater from beneath the site
<br /> Pumping occurred primarily from well MW-1 R
<br /> In November 2001, SECOR conducted a five-day dual-phase extraction (DPE) test to
<br /> reduce the amount of petroleum hydrocarbons in soil and groundwater beneath the site,
<br /> and to determine the feasibility of DPE as an applicable technology for remediation at the
<br /> site DPE tests were performed on well MW-1R for 3 hours, MW-2R for 3 hours, VW-1 for 2
<br /> hours, and simultaneously on wells MWA R, MW-2R, and VW-1 for 92 hours DPE was
<br /> conducted at vapor extraction flow rates ranging between 10 90 standard cubic feet per
<br /> minute (scfm) to 42 86 scfm, at vacuums ranging from 14 to 25 Inches of mercury, and at
<br /> groundwater extraction flow rates ranging from 0 01 gpm to 6 2 gpm During DPE testing,
<br /> an estimated 8 11 pounds of TPHg, 0 17 pounds of benzene, and 5 26 pounds of MtBE
<br /> were removed from beneath the site, and approximately 26,210 gallons of groundwater
<br /> were extracted and transported off-site for disposal The results of DPE testing Indicated
<br /> that this technology was ineffective based on the low soil vapor extraction radius of
<br /> • influence (24 feet), the large quantity of extracted groundwater, and low estimated mass
<br /> removal quantities (SECOR, 2002)
<br /> 1 Icon000PhillipslRetail Sites1111931Reports111193 Off-Site well Install 1-05 doc SECOR International Incorporated
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