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L' r Mr Kyle Christie August 24, 1995 Page 3 • TPH-G was not detected in wells E-12, PR-1, PR-2, BHD-2, MW-1, MW-3, and MW-4, but was detected in wells E-2, E-3, E-4, E-5, E-7, E-8, E-9, E-11, BHD-1, and MW-5 at concentrations ranging from 67 pg/l in well E-7 to 58,000 pg/L in well E-3 These results are consistent with previous results, with the exception of wells E-4, E-5, E-9, and E-12 The TPH-G concentration is higher than previously reported values in well E-4, and is lower than previously reported values in well E-5 The TPH-G concentration in well E-9 is the highest it has been since 1990 TPH-G was not detected in well E-12 for the first time since 1991 Analytical results of groundwater samples are summarized in Table 3 The complete laboratory report for the sampling event is presented in Exhibit A Figure 2 shows TPH-G and BTEX concentrations for this sampling event The hydrocarbon concentrations detected in BHD-1 are thought to be attributed to the Chevron station across the street from the ARCO site Chevron's well MW-1 is located approximately 30 feet to the north of well BHD-1 and near Chevron's former underground storage tank location Samples from Chevron's MW-1 have generally contained similar TPH-G and BTEX concentrations to those in BHD-1 Unauthorized Release Sometime during the second quarter 1995, an unauthorized release of free product occurred at the site As soon as ARCO suspected that a release may have occurred, a precision test • of the underground storage tank and piping system was coordinated by ARCO The results of the testing indicated that one of the product lines at the northern pump island was leaking The San Joaquin County Health Department (County) was immediately notified, the product line was taken out of service, and an Unauthorized Release/Leak Report was completed and submitted to the County Active removal of the free product began on July 14, 1995 The leak was repaired on July 19, 1995 At the direction of the County, a soil sample was collected from the product line trench beneath the area in which the leak occurred The analytical results of the trench samples indicate that hydrocarbons are present in the soil beneath the product line in the leak area The laboratory report for the trench sample is included in Exhibit B The free product identified in well E-10 is thought to be from this product line leak Status of Site Remediation This section provides a description of the remediation system and discusses the operation of the remediation system for the second quarter 1995 Description The remediation system at ARCO Facility 2133 consists of a groundwater extraction system (GWES) and a soil vapor extraction and treatment/air sparging (SUET/AS) system The GWES consists of one groundwater extraction well (R) fitted with a submersible pump, with a designed pumping capacity of 15 gallons per minute The extracted groundwater is discharged to the City of Stockton sanitary sewer under City of Stockton Use or disclosure of data contained on this sheet is subject to the restriction specified at the beginning of this document 20WREP0RTS2`rD95QTR RPT