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W. Luci Thater - 2 - 14 September 2006 336 Lc:cust St, Lodi, San Job ,,ain County hours t,ie pumping test was stopped due to drawdown below the pump intake of the water column in the casing of MW-1 The calculated maximum radii of influence (Figure 5) were: 94 feet (2 gpm), 122 feEt (3 gpm) and 118 feet (4 gpm). Since eastern boring B-3 is 19 feet from MW-1, it appears that the entre groundwater plume may be treated by extraction from this one well. Only Ethylbenzene (4.2 pg IL after one hour) and Xylenes (12.6 pg/L after one hour and 2.5 pg/L after 3 hours) were detected in groundwater sampled during the pump test. Constituents of concern were not detected in samples collected later in the pumping test. In contrast, the quarterly monitoring groundwater concentrations for TPHg in MW-1 were: 1,500 pg/L in February 2006, 800 pg/L in May 2006, and 1 200 1,g/L taken one week prior to the pumping test. Note that the pumping test was conducted one day after the SVE pilot study, which may have affected the analytical results of the pumping test. The Report concluded that groundwater pumping and treatment is an effective remedial alternative for petrole,im hydrocarbon pollution in groundwater. The RE port recommends that SVE and groundwater pump and treatment be implemented as an interim remediation, and the submittal of an Interim Remedial Action Work Plan. The Report also recommends the installation of one monitoring well located at soil boring B3, to monitor the eastern edge o' the groundwater plume. Comments. I concur with the Report conclusions and recommendations for an Interim Remediation consisting of SVE• aid groundwater pump and treatment, and the installation of one additional monitoring well east of MW-1. The proposed remediation is reasonable and necessary to remediate soil and groundwater beneath the Site, and to prevent vapor migration to neighboring residences surrounding the Site. Also, you have indicated in conversations that unless the remediation is expedited and completed by November 2006, the City of Lodi will revoke your building permit for your new residence at the Site. Please expedite and submit the Interim Remedial Action Work Plan by 25 September 2006, and be prepared to begin interim remediation by 29 September 2006. The treated water discharge will be under a City of Lodi permit to the sewer. The SVE treatment system must be constructed in a manner that is less than obtrusive to the residential neighborhood. The new monitoring well (MW-5) is also approved (as built to the specifications of existing MW-2 through MW-4), and must be installed no later than 15 October 2006. Acquire all applicable well and air permits, and provide at least 3 working days notice to San Joaquin County staff and myself prior to commencement of fieldwork. You may call me at (916) 464-4615 or email me at jbarton(a)_waterboards.ca.gov if you have questions. James L.L. Barton, P.G. Engineering Geologist 1 i . Attachments cc: Ms. Pat Preslar, State Water Resources Control Board, USTs OSCA Account, Sacramento Mr. Harlin Knoll, San Joaquin County Environmental Health Services, Stockton Mr. John Chung, KEO #6 LTD PTP, P.O. Box 7249, Newport Beach, CA 92658 Ms. Jo'I Chapman, Advanced GeoEnvironmental Inc., Stockton