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Mr. Carl W. Knowles, Succe3for Trustee Page 2 of 2 <br /> Knowles Family Trust May 11, 2010 <br /> Former Roek Construction <br /> 102 S. Wilson Way <br /> exceeding 40 feet below surface grade (bsg); this is beyond the reach of an ordinary excavation <br /> and soil vapor extraction (SVE) would not be appropriate. Also in the SCM, GZA offered their <br /> opinion that based on site conditions, groundwater extraction (GWE), insitu air sparging and <br /> ozone sparging were not likely to effectively address the residual contaminants, but that <br /> chemical oxidation may be feasible. <br /> Ozone injection has been utilized on the adjacent ARCO site (130 S. Wilson Way) to remediate <br /> groundwater impacted primarily by methyl tert-butyl ether (MTBE), and the site is nearing <br /> closure consideration. The former Top Filling site across the street at 101 S. Wilson Way has <br /> been remediating impacted soil and groundwater through SVE and groundwater extraction; the <br /> data supports estimates that a significant portion of the contaminant mass has been removed. <br /> Based on the rational provided by GZA and the apparent success of the ozone injection at the <br /> ARCO site which strengthens the possibility that chemical oxidation may be beneficial on your <br /> site, the EHD approves your pilot test with the following provision: <br /> • After the initial injection event, sample each injection well immediately prior to each <br /> subsequent injection event for the first three months; <br /> • Analyze the samples for potentially harmful byproducts that would be identified through <br /> the proposed, and now approved, analytical regimen; and <br /> • You shall have an approved contingency plan of action in the event that harmful <br /> byproducts are encountered. <br /> The work plan states that a permit will be applied for under the Central Valley Regional Water <br /> Quality Control Board (CVRWQCB) Order R5-2008-0149. The EHD recommends that you <br /> initiate the application process with the CVRWQCB right away to ascertain their permit <br /> requirements and to minimize delay acquiring the permit. The monitoring and reporting program <br /> required by the CVRWQCB for the permit may entail additional sampling and analyses. <br /> Questions or comments may be directed to Nuel Henderson at (209) 468-3436. <br /> Sincerely, / <br /> 401wo-- ./71A <br /> Nuel C. Henderson, Jr., PG — AkJrnne Ellsaesser, REHS <br /> Engineering Geologist Acting Program Coordinator <br /> C: James Barton, CVRWQCB 11020 Sun Center Dr. #200, Rancho Cordova, CA 95670 <br /> Gregory Stahl, GZA, 1714 Main Street, Escalon, CA 95320 <br /> Mohammid Asghar, 601 Wade Ave., Modesto, CA 95351 <br /> Tasnim Akhtar, 1514 E. Market St., Stockton, CA 95205 <br /> Work Plan Approval Letter 0510 <br />