SITE INFORMATION AND CORRESPONDENCE

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L",'IS San Joaquin County DIRECTOR Environmental Health Department Donna Heran, RENS 600 East Main Street _ Stockton, California 95202-3029 PROGRAM COORDINATORS S { Robert McClellon,REHS • ` I — Jeff Carruesco,RENS, RDI r.- Kasey Foley, REHS cQ�1FOR��P Website: www.sjgov.org/ehd Linda Turkatte,REHS Phone: (209) 468-3420 Fax: (209) 464-0138 February 6, 2012 Ms. Mary E. Sanchez 1633 W Walnut Street Stockton CA 95203 Subject: Former UST LOP Case#: 1844 1876 Country Club Blvd. CUF#: 1026 Stockton, CA 95203 Global ID#: T0607700260 The San Joaquin County Environmental Health Department (EHD) has reviewed Western GeoEngineers' Work Plan for Site Restoration (Pian) dated January 19, 2012. on Geotracker. The Plan was submitted to address the destruction of the wells in preparation for receiving a No Further Action status. The Plan proposed both pressure grouting and drilling out the wells. The EHD has reviewed the most recent groundwater laboratory data (May 2011) for this site and provides a modification to the Plan. Monitoring wells MW-2, MW-4, MW-8A, MW-8B, and MW-9a are to be drilled out along with MW-6A and the five SG wells as proposed in the Plan since contamination was still present in the groundwater and vapor samples at the wells last sampling event. Monitoring wells MW-3, MW-5, MW-6B, MW-7A, MW-7B, and MW-9B may be pressure grouted per procedures included in the Plan. Monitoring well MW-10 is a 27-foot deep, 4-inch PVC well construction through pea-gravel in the former underground storage tank (UST) pit. A 12-inch diameter by 4-foot deep steel conductor casing was installed at the surface of this well, just below the 3-foot deep traffic vault. The last sampling event data for this well indicated that this well contained contaminants, which have been present in water samples from this well since its installation in 2004. As such, this well is not qualified for pressure grouting. The Plan included a proposal for this well that provided for filling the casing with cement grout under pressure and allowing the grout to Stabilize at the bottom of the 3-foot deep traffic box. The traffic box would then be backfilled with clean road base to an asphalt surface seal. The EHD has evaluated the proposed procedures for MW-10 and will not allow pressured cement grout and a soil surface fill for this well. The EHD is of the opinion that adding cement grout to a pea-gravel subsurface will cause more problems than it solves. The contents of MW-10 are to be removed to 28 feet below ground surface ('bgs). The EHD requires a cement seal to be placed below the pea-gravel; from 28' bgs to 24' bgs. In addition, the EHD requires that pea gravel be used to backfill the boring after the contents of MW-10 have been removed. This can be accomplished in two ways.