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fr Mr Chuck Carmel September 6, 1994 Page 2 Quarterly Sampling Results and Discussion GTI's field notes and the analytical report from the quarterly groundwater sampling are contained in Exhibit A Table 1 presents the water-level data for this site Table 2 summarizes historical groundwater flow direction and gradient data for this site Figure 1 shows the water-level elevations for each well and the contours of equal water-level elevation for June 27, 1994 Figure 2 shows BTEX and TPH-G concentrations for each well sampled, and the approximate extent of benzene in the groundwater Table 3 presents the groundwater analytical data On June 27, 1994, the general groundwater flow direction was northeast with influence by the GWES Historically, groundwater flow direction is to the northeast under an average hydraulic gradient of 001 to 003 Water-level elevations have increased an average of 0 15 feet since the last quarterly monitoring (March 1994) The TPH-G and BTEX concentrations detected in the samples collected this quarter are generally consistent or lower than previously reported results in wells E-2, E-3, E-4, E-5, E-6, E-7, E-8, E-9, E-10, E-11, E-12, BHD-1, and MW-2. 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. The samples from off-site wells PR-1, PR-2, BHD-2, and on-site well MW-1 did not contain detectable concentrations of hydrocarbons, indicating that off-site migration is being contained by the GWES. 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 1994 Description. The remediation system at ARCO Station 2133 consists of a GWES. The GWES consists of one groundwater extraction well with a designed pumping capacity of 15 gallons per minute The extracted groundwater does not require treatment prior to discharge to meet the requirements of the City of Stockton wastewater discharge permit issued for this site. The system is sampled monthly to ensure the discharge is within permitted limits. The analytical results are included in Exhibit B. Groundwater is extracted from the well via a submersible pump Installation and start-up of a free product recovery system occurred in 1984 After the free product was recovered, the system was modified for use as j Use or disclosure of data contained on this sheet is subject to the restriction specified at the beginning of this document 12731REP0RTSUND94QTRJd7r