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r <br /> • San Joaquin County • DIRECTOR <br /> Donna Heran,REHS <br /> Environmental Health Department <br /> 2 , 2 ASSISTANT DIRECTOR <br /> I ` 600 East Main Street Laurie Cotulla, REHS <br /> Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> Carl Borgman, REHS <br /> c4�IFo'R`'�P Mike Huggins,REHS, RDI <br /> Website: www.sjgov.org/ehd Margaret Lagorio, REHS <br /> Phone: (209) 468-3420 Robert McClellon,REHS <br /> Fax: (209)464-0138 Jeff Carruesco, REHS, RDI <br /> Kasey Foley, REHS <br /> GEORGE AND MEI TERANISHI JUL 0 9 2007 <br /> 1600 DURHAM FERRY RD <br /> TRACY CA 95376 <br /> RE: GEORGES SERVICE Site Code: 1550 <br /> 1600 DURHAM FERRY RD <br /> TRACY CA 95376 <br /> San Joaquin County Environmental Health Department (EHD) has received and <br /> reviewed Remediation Investigation Report, In Situ Remediation Pilot Test(Test Report), <br /> Additional Groundwater Analysis (AGA), and Groundwater Monitoring Report 4tn Quarter <br /> 2006 (QMR) dated 30 October 2006, 22 January 2007, and 04 January 2007, <br /> respectively, prepared on your behalf by your consultant Geological Technics, Inc. (GTI). <br /> The Test Report and AGWA show that hexavalent chromium, (Cr"') occurs in <br /> groundwater near and on your site and that none or little of the Cr*6 appears to have <br /> been generated by the limited use of ozone on your site during a pilot test. Due to the <br /> presence of Cr+6 in groundwater samples collected from your site, the Central Valley <br /> Regional Water Quality Control Board (CVRWQCB) indicated that it is very unlikely that <br /> the CVRWQCB would approve use of ozone for groundwater remediation on your site as <br /> such use may exacerbate the Cr 16 production and its impact to groundwater. You must <br /> therefore propose another remediation method to address groundwater impacted by the <br /> unauthorized release on your site. Present a feasibility study for groundwater <br /> remediation to the EHD by 04 September 2007. <br /> The EHD reviewed your site data and has determined that the vertical extent of <br /> impacted groundwater has been demonstrated on site by the analytical results from <br /> groundwater samples collected from monitoring wells MW-2X, MW-101, MW-105 (all <br /> screened approximately 32 to 35 feet below surface grade), MW-102, MW-107 and <br /> MW-201 (screened approximately 45 to 52 feet below surface grade) and MW-202 <br /> (screened 79 to 81.5 feet below surface grade). The off-site well, MW-106 (screened 32 <br /> to 34.5 feet bsg), is impacted by methyl tert-butyl ether (MTBE) and 1,2-dichloroethane <br /> (1,2-DCA), which GTI interprets to indicate the plume is `diving' as it migrates northward, <br /> - an interpretation that has EHD concurrence. <br /> Laterally, the dissolved plume impacting shallow zone wells, generally screened from 7 <br /> to 22 feet below surface grade (bsg), is delineated toward the north by MW-6 and MW-7, <br /> toward the south by MW-3, and MW-8 appears to be on the east plume margin. <br /> The impacted groundwater in MW-106, screened between 32 and 34.5 feet bsg, is not <br /> delineated except to the south in the source area. A sentinel well near the 31488 Hwy 33 <br /> domestic well screened in the sand unit monitored by MW-106 is needed. A similar <br />