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! i <br /> San Joaquin County <br /> °"'" .� Environmental Health Department DIRECTOR <br /> .o Donna Heran,REHS <br /> 1868 East Hazelton Avenue <br /> PROGRAM COORDINATORS <br /> Stockton, California 95205-6232 Robert McClellan, REHS <br /> .. Jeff Carruesco,REHS, RDI <br /> • 0'.. .. 'a`P Website: www.SJgov.org/ehd Kasey Foley,REHS <br /> C F o d Linda Turkatte, REHS <br /> Phone: (209) 468-3420 Rodney Estrada,REHS <br /> Fax: (209) 464-0138 Adrienne Ellsaesser,REHS <br /> March 25, 2013 <br /> 4l 1 -7 <br /> Ms. Cat ine-KbWer �'w�ht��fi� V)hCej V"e_4" "' Mr. George Betker <br /> Equipment Company, Inc. Geo Properties, Inc. <br /> 321 Spreckles Avenue 2306 Jackie Court <br /> Manteca, California 95336 Oakdale, California 95361 <br /> Subject: Former J.M. Equipment Company LOP Case No.: 9401 <br /> 1245 West Charter Way CUF No.:12607 <br /> Stockton, California 95206 GeoTracker ID No.: T0607700794 <br /> Dear Ms. Kahler and Mr. Betker: <br /> By email dated 31 January 2013, your consulting firm, Ground Zero Analysis, Inc. (formerly <br /> Geological Technics, Inc.) requested that the San Joaquin County Environmental Health <br /> Department (EHD) evaluate the above-referenced site under the Low Threat Closure Policy <br /> (LTCP). In response, the EHD completed the LTCP checklist in GeoTracker, the database <br /> website operated by the California State Water Resources Control Board, and has identified the <br /> following impediments to site closure: <br /> • Benzene was detected at 7,500 micrograms per liter (Ng/L) and 14,000 pg/L in <br /> monitoring wells MW-5 and MW-9, respectively, and 1,200 pg/L, 1,400 pg/L and 5,600 <br /> pg/L in observation wells OW-1, OW-2 and OW-3, respectively, during the most recent <br /> sampling event completed on 28 June 2012. These concentrations far exceed the <br /> Water Quality Objective of 0.15 pg/L for benzene listed in Appendix A of the Tri-Regional <br /> Board Staff Recommendations for Preliminary Investigations and Evaluation of <br /> Underground Tank Sites, dated 16 April 2004, prepared by the California Environmental <br /> Protection Agency Regional Water Quality Control Board Central Valley Region; and <br /> exceed the benzene concentrations of 1,000 pg/L and 3,000 pg/L presented in the LTCP <br /> checklist. To date, remediation has not been implemented at this site; therefore, the <br /> EHD concludes that a secondary source of contamination has not been removed to the <br /> extent practicable. <br /> • Soil samples collected in the former underground storage tank secondary source area at <br /> five to ten feet below surface grade (bsg) are limited to one sample collected during the <br /> installation of monitoring well MW-9 in 1996. Benzene was detected at 0.039 milligrams <br /> per kilogram (mg/kg) at 5.5 feet bsg; but at 10.5 feet bsg, benzene was reported at 2.14 <br /> mg/kg. Also in nearby soil boring SB-109, benzene was detected at 1.73 mg/kg at 10.5 <br /> to 11 feet bsg. There does not appear to be enough soil data from the secondary source <br /> area to adequately demonstrate the existence of a ten-foot bicattenuation zone with less <br />