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Ms Margaret Lagono S E C ® R <br /> August 1, 2005 l <br /> Page 3 <br /> underground utility search (ERI, October 6, 1997), 2) performed quarterly groundwater <br /> monitoring and sampling, 3) obtained access agreements to drill soil borings at select <br /> properties located south and southwest of the site, 4) requested Sequoia Analytical <br /> Laboratories (Sequoia) to review chromatograms of groundwater samples collected <br /> during the September 1995 Geoprobe® investigation (Delta, February 6, 1996) in order <br /> to estimate methyl tertiary butyl ether (MtBE) concentrations in groundwater <br /> (ERI, March 2, 1999) <br /> February 1999 - Tosco advanced three off-site cone penetrometers (CPT1 through <br /> CPT3) and drilled three off-site soil borings (138 through B10) (ERI, March 2, 1999) <br /> April 1999 - Tosco installed nine off-site groundwater monitoring wells consisting of three <br /> nested wells (shallow, intermediate, and deep) at each of three well locations <br /> (ERI, June 9, 1999) <br /> May 1999 - ERI submitted a report entitled Air Sparge/Sort Vapor Extraction (AS/SVE) <br /> Test, dated October 18, 1999, presenting the data collected during the AS/SVE <br /> feasibility test <br /> December 28, 1999 - ERI submitted a Corrective Action Plan (CAP) Tosca received a <br /> letter from the San Joaquin County Public Health Services department (the County) <br /> dated February 22, 2000, approving the remediation recommendations provided in ERI's <br /> December 28, 1999 CAP as an Interim Remedial (IR) Action document <br /> During second quarter 2000, ER] installed one UST cavity well in general accordance <br /> with the CAP (ERI, December 28, 1999) Periodic purging of groundwater from the UST <br /> cavity well and from groundwater monitoring well MW3 was also initiated Groundwater <br /> purging was temporarily discontinued during third quarter 2000, pending clarification <br /> from the County regarding water sampling and data collection requirements Purging <br /> was resumed during January 2001, and continued through January 2002, when it was <br /> terminated following installation and operation of the microsparge remediation system <br /> Approximately 285,000 gallons of groundwater were purged from the UST cavity well <br /> and well MW3 and transported to the Tosco refinery for recycling during interim <br /> groundwater remediation efforts <br /> During June 2001, Tracer Research Corporation performed an enhanced leak detection <br /> test on underground storage systems to evaluate the system integrity According to <br /> Tosco, the results of the enhanced detection test indicated that the underground storage <br /> systems are functioning within acceptable parameters <br /> During third quarter 2001, ERI submitted an additional CAP, dated September 25, 2001 <br /> The CAP included recommendations to install a microsparge system to remediate MTBE <br /> impacted groundwater beneath the site <br /> During first quarter 2002, the microsparge remediation system was completed and ERI <br /> performed system startup and initiated monthly operation and maintenance (O&M) of the <br /> system <br /> Currently, there are 10 on-site AS wells (ASI through AS5, AS7, AS8, and AS10, and <br /> nested wells AS6S/D and AS9S/D), three on-site, single-casing groundwater monitoring <br /> 5886 2Q2005 QSSR SECOR International Incorporated <br />