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San Joaquin County <br /> N DIRECTOR <br /> Environmental Health Department Donna Heran,REHS <br /> 600 East Main Street t <br /> u¢i .X Stockton California 95202-3029 PROGRAM COORDINATORS <br /> its <br /> Stockton, Robert McClellon,REHS RS REHS <br /> Jeff Carruesw,REHS,RDI <br /> Kasey Foley,REHS <br /> Website:www.Sjgov.org/ehd unda Turkatte,REHS <br /> L'FOR� Phone: (209)468-3420 <br /> Fax: (209)464.0138 <br /> November 15, 2010 <br /> Ms. Catherine Kahler <br /> JM Equi pTment Co Inc. <br /> 819S. 9 H St. <br /> Modesto, CA 95351 <br /> Subject: JM Equiipment LOP Case#: 9401 <br /> 1245 W. Charter Way CUF#: 12607 <br /> Stockton, CA. 95206 Geotracker IN: T0607700794 <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed <br /> Remedial Action Plan (RAP) dated July 30, 2010, that was submitted by your consultant, <br /> Geological Technics Inc. The RAP included a comprehensive evaluation of the site's <br /> historical investigations up to the most recent sampling event (second quarter 2010). <br /> Also included was review of the feasibility study originally included in the November <br /> 2009 Site Conceptual Model that evaluated multiple remedial alternatives for cleaning up <br /> contaminated underground storage tank sites. <br /> Conclusions in the RAP stated that the installation of large diameter boreholes (LDB) in <br /> conjunction with in-situ chemical oxidation (ISCO) would be the most feasible and cost- <br /> effective remedial alternative for reducing the contaminant mass in the soil and <br /> groundwater at this site. A pilot test with four LBDs and one observation well installation <br /> was recommended to evaluate the effectiveness of the remedial alternative. <br /> The pilot test discussed the installation of two 36-inch diameter LDBs by bucket auger <br /> drilling and two LDBs with 18-inch hollow stem augers. The first boring, "LDB-1" would <br /> be installed to 23 feet below ground surface ('bgs), approximately 15 feet west of MW-9 <br /> and MW-5. A commercial oxygen releasing compound, ORC, would be added at the <br /> bottom of the boring and the boring would be filled from the bottom to 15' bgs with a <br /> highly permeable backfill (pea gravel). A 2-foot bentonite seal would be emplaced <br /> before additional pea gravel would be added, filling LDB-1 to the surface, where a <br /> concrete cap would be applied. A second LDB, "LDB-2" would be installed in the ring <br /> area of the plume (between MW-5 and MW-9) utilizing the 36-inch diameter bucket <br /> auger with construction similar to LDB-1. An observation well, "OW-2", is to be installed <br /> 3.5 feet down-gradient (northeast)of LDB-2, to 25' bgs with a 15-foot screened interval. <br /> The last two LDB borings, "LDB-3" and "LDB-4" are proposed to be installed inside 18- <br /> inch hollow stem auger boreholes to 23' bgs. "A perforated pipe will be installed in each <br /> 18"diameter borehole. The purpose of the perforated pipe will be to provide access to <br /> the subsurface for further introduction of oxygen releasing compounds and/or air or for <br /> groundwater monitoring." <br />