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, z v5 2 -�® �a San Joaquin County DIRECTOR P Au' Environmental Health Department Donna Heran,REHS n M ASSISTANT DIRECTOR r. s 600 East Main Street Laurie Cotulla,REHS U1. < Stockton, California 95202-3029 PROGRAM COORDINATORS Carl Borgman,REHS Website:www.SJgov.or ehd Mike Huggins,REHS,RDI c4 L b aN�P Margaret Lagorlo,REHS Phone: (209)468-3420 Robert McClellon,REHS Fax: (209)464-0138 Jeff Carruesco,REHS,RDI Kasey Foley,REHS March 23,2009 John and Margaret Marci 20 Mobile Lane Crescent City,California 95531-8409 Subject: John and Margaret Marci Property 2969 Loomis Road Stockton,California 95205 The San Joaquin County Environmental Health Department (EHD) has reviewed Revised Work Plan - Additional Dual Phase Extraction Pilot Test, (revised work plan) dated January 23, 2009, prepared by Geological Technics Inc. (GTI) on your behalf. The revised work plan was submitted in response to the EHD letter dated December 31, 2008,recommending several modifications to the original work plan involving dual phase extraction(DPE). In the revised work plan, GTI proposes to install three additional extraction wells (EW-4, EW-5, and EW-6) at locations illustrated on Figure 2. The proposed extraction wells will be used to conduct three DPE pilot tests using high vacuum technology to simultaneously extract groundwater and soil vapor. GTI proposes the DPE tests to last five days at each proposed extraction well with nine-day breaks between tests to allow equilibrium conditions to be reestablished. During each pilot test, GTI proposes to collect three gas and three groundwater samples to be analyzed for benzene, toluene, ethyl benzene, and total'xylenes (BTEX); total petroleum hydrocarbons quantified as gasoline MH-G), and total petroleum hydrocarbons quantified as diesel (TPH-D). GTI proposes to monitor vacuum influence, volatile organic compound concentrations using a photo ionization detector(PID), and depth to groundwater in observation wells MW-4,MW-5,and MW-7 for all three pilot tests. Other wells to be monitored during one or more pilot tests include injection wells IW-1, IW-101 and extraction wells EW-1, EW-101, EW-2, EW-102, EW-3 and EW-103. The EHD approves the installation of proposed dual phase extraction wells EW-4, EW-5, and soil vapor extraction well EW-6. All three wells will be constructed using ten-inch diameter augers and four-inch diameter casings. EW-4 will be screened between forty-five and seventy feet below surface grade (bsg); EW-5 will be screened between thirty and fifty feet bsg; and EW-6 will be screened between ten and thirty-five feet bsg. The EHD recommends the annular seal be approximately three feet for each well instead of the proposed ten feet for EW-4 and eight feet proposed for EW-5. Also, soil and groundwater generated during drilling must be analyzed for chemicals of concern, and contained in properly labeled•Department-of-Transportation-approved fifty-five gallon drums,and stored on site until proper disposal. _ 3 3 N, A-C Y n-6.g b s a^^-.��G S -�- I vJ q�e Y