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i � i15 May 2001 AGE-NC Project No 97-0333 ' Page 6 of 7 D, E and F) • Utilizing a semi-loganthmic plot of ground water draw- down vs observation well distance to pumping well(Jacob straight-line method),a best-fit line can be utilized to project a radius of influence of approximately 140 feet at 6 GPM (Appendix H) • Utilizing the Distance-Drawdown Method (Jacob straight-line method), a transmissivity was ' calculated at 955 ft'/day (equivalent to 7,127 gallons per day/ft) and a storativity value calculated at 0 032 (Appendix I) • Based on a transmissivity value of 955 ft'/day and the First Water Zone aquifer thickness ' equaI to 25 ft(screen interval at EW-1),a hydraulic conductivity value was calculated at 38 2 ft/day, or 0 0135 cm/s (Appendix 1), a hydraulic conductivity of 0 0135 cm/s is consistent with a screened interval located within a well sorted sand to clean sand (Appendix L) • Laboratory analysis of extracted water during the pumping test detected elevated concentrations of TPH-g, BTEX, MTBE and TAME, TPH-d was detected, however, the laboratory reported the sample chromatogram as a non-diesel pattern and significant lighter range gasoline compounds (Appendix J) 5.0 RECOMMENDATIONS By letter dated 02 March 2001, the RWQCB directed the Rainwater Car Wash to install and continuously operate an interim pump and treat system in the area of the most-intense on-site ground water contamination Based on the 05 April 2001 ground water aquifer pumping test results, AGE recommends interim remediation by extracting petroleum-impacted ground water from EW-1 at approximately 6 GPM, based on the site's estimated radius of influence of at least 140 feet and site specific aquifer ' characteristics inferred from the pumping test, AGE believes that ground water extraction from well EW-1 at 6 GPM will effectively stabilize the groundwater plume and inhibit further migration of petroleum-impacted ground water off-site until a full-scale ground water remediation system can be ' implemented Extracted ground water from EW-1 could be treated through an on-site two-stage ground water pump-and-treat system The first stage of the ground water pump and treat system would utilize granular activated carbon (GAC) to address TPH-g, TPH-d and BTEX in extracted ground water, the second stage of treatment would address MTBE utilizing SunSolve, a patented material that has ' an affinity to absorb MTBE Following treatment, water could then be discharged into the City of Manteca sewer system under a City of Manteca Public Works permit ' 4dvaiared C,coEntiironmLotjl Inc