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San Joaquin County <br /> Environmental Health Department DIRECTOR <br /> Y Donna Heran,REHS <br /> 600 East Main Street <br /> _ - /��. '2� PROGRAM COORDINATORS <br /> W` :-'` :< Stockton, California 95202-3029 Robert McClellon,REHS <br /> Jeff Carruesco,REHS,RDI <br /> i <br /> �.,cq • . ,,.��P Website:www.sjgov.org/ehd Kasey Foley,REHS <br /> lrFOR Phone: (209)468-3420 <br /> Fax: (209)464-0138 <br /> June 10, 2010 <br /> Stephanie McKenna <br /> Chevron Environmental Management Company <br /> 6111 Bollinger Canyon Road, Suite 3652 <br /> San Ramon, CA 94583 <br /> Subject: Unocal #0187/Chevron Site ID 306415 <br /> 437 East Miner Avenue <br /> Stockton, CA 95202 <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed Enhanced <br /> Anaerobic Biological Oxidation Pilot Study, Pre-Design Investigation Work Plan (Work Plan) <br /> dated February 2010, and Response to Comments (Response) dated May 27, 2010, both <br /> submitted on your behalf by Arcadis and has the following comments. <br /> The Work Plan proposes conducting a pilot test to study the efficacy of using enhanced <br /> sulfate reduction to mitigate onsite contamination in the previously identified water bearing <br /> Zones A and B. Prior to submittal of a final pilot study design work plan, Arcadis requests <br /> approval to conduct further subsurface characterization of the proposed pilot study area. The <br /> scope of work proposed to accomplish this includes: four cone penetrometor test (CPT) <br /> borings to 70 feet below surface grade (bsg) and three soil borings utilizing injection logging; <br /> installing twelve injection wells clustered in five locations and three groundwater monitoring <br /> wells clustered in one location; and collecting soil and grab groundwater samples during the <br /> drilling of the borings. <br /> In the Response, Arcadis provides detail on the proposed injection monitoring, and modifies <br /> the original proposed scope of work. The EHD approves the following: <br /> 1. Installation of six soil borings utilizing a hydraulic profiling tool (HPT) to perform the <br /> injection logging that will develop a continuous vertical profile of the subsurface. The <br /> HPT borings will be approximately 70 feet deep. No CPT work will be done. <br /> 2. Installation of three groundwater monitoring wells in a cluster on the eastern side of <br /> the site. <br /> 3. Installation of twelve injection wells clustered in five locations along a transect <br /> crossing the property. <br /> 4. Soil samples for analyses will be collected during the drilling of the boreholes; no grab <br /> groundwater samples will be collected during drilling activities. <br /> In addition to the above outlined scope of work, Arcadis will perform baseline analyses of the <br /> groundwater for petroleum hydrocarbon constituents, sulfate, nitrate, total and dissolved iron <br /> and manganese, methane and forensic analyses. The EHD does not approve any offsite <br /> work during this phase of investigation, as it will not provide data specifically relevant to the <br /> targeted pilot study area, and because the proposed location is not impacted by the <br /> contaminant plume from this site. <br />