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M Hartzell - Project No 1232 October 18, 2000 • Page 2 of 4 Site Address Distance to Well Site feet Exxon 4404 Pershin&Avenue 3600 Shell 4445 Pershing Avenue 3600 7-11 Store 4501 Pershing Avenue 3400 EAI reviewed available records maintained by San Joaquin County for these sites Ground water beneath all of these sites has been impacted and monitoring and remediation wells are present at all sites Only the Exxon site has free-product on the surface of the ground water Ground water beneath these sites, when converted to mean sea level data is present at approximately the same depths as the Wards and Unocal sites The deepest ground water well installed was 78 feet bgs, for well MW-1 at the Arco site Since San Joaquin County requirements will preclude slots in the New Irrigation Well at depths less than 200 feet bgs, including properly sealing the upper zone from pollution, e g, conductor casing, it is unlikely that the New Irrigation Well will impact any of these sites However, as a precaution, during pump tests to be conducted for the New Irrigation Well, pressure transducers/data loggers will be installed in selected wells for the Unocal site located at 4707 Pacific Avenue, and the Wards site Data from this study will determine if use of the New Irrigation Well impacts these sites • 2.0 TEST BORING Since the existing RIW is slotted at various depths between 40 feet bgs and 322 feet bgs, and the New Irrigation Well can not be slotted at depths shallower than 200 feet bgs, a test boring is required to determine the construction details for the New Irrigation Well, in order to ensure that the same volume of water supplied by the R1W taken out of service, will be supplied by the New Irrigation Well A test boring six-inches in diameter is proposed to a depth of at least 400 feet bgs at the proposed location of the New Irrigation Well (see Figure 1) The test boring will be E-logged and water samples will be collected for analytical testing from potential aquifers bottom to top These water samples will be selectively analytically tested for chemical constituents, i e , TPH-G by modified EPA Method 8015 and VOCs including fuel oxygenates by EPA Method 8260B, and for the following general irrigation parameters, carbonate, bicarbonate, chloride, sulfate, nitrate, calcium, magnesium, sodium, electrical conductivity, pH and boron Soil samples also will be collected for sieve analysis Data obtained nom this activity wili be uses to determine the specitic construction details for the New Irrigation Well These construction details, along with the San Joaquin County permit application to install the New irrigation Well, and the proposed pump testing of the well, including an NPDES permit application for discharge of water from the pump test, will then be submitted to the RWQCB and San Joaquin County for review and approval ENV RONMENTAL AUDIT, INC®