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15600 Harlan Road , *- Page 2 <br /> Lathrop, CA August 19, 2008 <br /> The EHD must request concurrence from the Central Valley Regional Water Quality Control <br /> Board (CVRWQCB) on closure determinations. On August 2, 2007, Jim Barton from the <br /> CVRWQCB and I met with Sarah Salcedo and Gowri Kowtha from Stratus Environmental. At <br /> the meeting It was discussed that remediation by natural attenuation was probably not viable <br /> and that groundwater extraction and treatment may be the most viable option for the site. <br /> There has been little change in site conditions since that meeting. In June 2007, the highest <br /> MTBE concentrations were in water samples from MWO-1X (190 micrograms per liter) and in <br /> June 2008 the highest MTBE concentrations were in water samples from MWO-1X (120 <br /> micrograms per liter). The groundwater contaminant plume still covers the entire 3.77 acres <br /> north of the site. Although, tests for dual phase extraction and groundwater extraction were <br /> performed in June 2004 and December 2005, active remediation has not been performed to <br /> control the migration of the contaminant plume. The plume is not defined to the north (water <br /> samples from MW15A still have detections of MTBE) nor to the northwest (last sample from <br /> MW13A1B was 110 micrograms per liter). At the August 2007 meeting it was agreed that <br /> Stratus would prepare and submit a Site Conceptual Model for the site as well as a Final <br /> Remediation Plan and to date neither of these documents have been submitted to the EHD. If <br /> continuous remedial action is not cost effective then evaluation of shorter term remedial actions <br /> should be considered. <br /> The EHD was informed on August 14, 2008, that MW 13AS and MW 13C had been found and <br /> restored and would be sampled on September 10, 2008. Data from these wells is necessary to <br /> determine if the contaminant plume is defined to the northwest and if contaminant <br /> concentrations are declining in that direction. <br /> in the Stratus Environmental, Inc. letter dated July 3, 2008, it states that Stratus would like to <br /> submit a work plan to evaluate soil vapor migration. The EHD approves of this proposal. The <br /> vapor investigation should include assessment of both of the former underground storage tank <br /> locations at the site as well as near buildings and off-site in the area of MW8. <br /> If you have any questions contact me at(209)468-3449. <br /> Margaret agorio, REHS <br /> Program Coordinator <br /> cc: Jim Barton, CVRWQCB <br /> Sarah Salcedo,Stratus Environmental Inc., 3330 Cameron Park Dr. Ste 550, Cameron <br /> Park, CA 95682 <br />