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E"RONMENTAL COST MANAGEMENT,INC. <br /> 3525 Hyland Avenue,Suite 200 <br /> Costs Mass,California 92626 <br /> Main:1714)662-2759 Fax:(714)662-2758June 15, 2015 <br /> Mr. Marcus Pierce, Engineering Geologist <br /> Central Valley Regional Water Quality Control Board <br /> 11020 Sun Center Drive, #200 <br /> Rancho Cordova, CA 95670-6114 <br /> Subject: Addendum Work Plan for Supplemental ISCO Injections <br /> California Army National Guard Field Maintenance Shop #24 <br /> Stockton, California <br /> Contract W912P7-12-D-0001, Task Order CQ01 <br /> Dear Mr. Pierce: <br /> Environmental Cost Management, Inc. (ECM) is submitting this Addendum Letter Work Plan for <br /> Supplemental ISCO Injections (Work Plan) to the Central Valley Regional Water Quality Control <br /> Board on behalf of the California Army National Guard (CA ARNG), under U.S. Army Corps of <br /> Engineers (USACE) Los Angeles District Contract W912P7-12-D-0001, Task Order CQ01, <br /> Amendment 0001. This Work Plan represents an addendum for the Work Plan for Implementing <br /> Remedial Action by In-Situ Chemical Oxidation (ISCO) submitted by ECM on June 2014. <br /> This Work Plan is a formal request to continue injection of PersulfOx and ORC-A in accordance <br /> with the approved 2014 Work Plan and the Notice of Applicability (NOA) of General Order No. <br /> R5-2008-0149-045 (CVRWQCB, 2013). The ISCO injection will occur within the 2,500 square <br /> foot area and injection interval as the prior 2014 injection. <br /> The work will include injection of PersulfOx and ORC-A by Regenesis through direct push <br /> technology (DPT) over an area of approximately 2,500 square feet. ECM will advance a total of <br /> twenty-eight(28) injection points over two injection events of fourteen (14) injections each. At five <br /> (5) locations we will core and inject beneath the existing UST concrete anchor slab. The proposed <br /> locations for the injection points are provided in Figure 1 attached. ECM will deliver the injectants <br /> between 35 feet (ft.) to 55 ft. below ground surface (bgs). The 2015 ISCO injection is scheduled <br /> for the week of July 6th thru July 10th and August V thru August 7th 2015. <br /> ECM proposes to collect a soil sample near MW-5 that is within the center of the contaminant <br /> area and additional groundwater samples from MW-5, MW-6 and MW-7 using passive diffusion <br /> bags (PDBs) at various depths. These samples will be analyzed for TPH-g, BTEX, and VOCs <br /> (naphthalene and fuel oxygenates) by USEPA Method 8260B. The analytical results of these soil <br /> and groundwater samples will be used for internal purposes only to further define injection interval <br /> volumes and target areas. The soil and groundwater sampling activities are scheduled for June <br /> 30, 2015. <br /> ECM will perform this work in accordance with the June 2014 Work Plan for Implementing <br /> Remedial Action by In-Situ Chemical Oxidation (ISCO), including the Quality Assurance Project <br /> Plan (QAPP) and the project Accident Prevention Plan/Site Safety and Health Plan (APP/SSHP). <br />