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AECOM 805.388.3775 tel <br /> AX0M 1220 Avenida Acas 805.388.3577 fax <br /> Camarillo,CA 93012 <br /> w .aemrn.com <br /> October 27, 2010 <br /> Mr. James L. L. Barton <br /> Regional Water Quality Control Board —Central Valley <br /> 11020 Sun Center Drive, Suite 200 <br /> Rancho Cordova, California 95670-6114 <br /> Subject: Semi-Annual Groundwater Monitoring and Remediation Status Report <br /> for the Third Quarter of 2010 <br /> Cleanup and Abatement Order No. 5-00-707 <br /> 5400 and 5606 Pacific Avenue, Stockton, California <br /> Chevron#306620 (former Unocal #5098) <br /> AECOM Project#60146576-GWR <br /> Dear Mr. Barton: <br /> AECOM, on behalf of Chevron Environmental Management Company (CEMC), is submitting the <br /> Semi-Annual Groundwater Monitoring and Remediation Status Report for the Third Quarter of 2010. <br /> This report documents the second semi-annual monitoring event activities for the former Montgomery <br /> Ward, LLC (Wards) auto service center located at 5400 Pacific Avenue and former Unocal Service <br /> Station #5098 located at 5606 Pacific Avenue, Stockton, California (Figure 1),which are referenced <br /> collectively as the Site. The locations of former and current Site features are presented on Figure 2. <br /> Groundwater monitoring and sampling and remediation activities have been conducted pursuant to <br /> requirements of Cleanup and Abatement Order(CAO) No. 5-00-707 issued to Wards, Unocal, Surry <br /> California Limited Partnership, and Stone Brothers and Associated General Partnership (Stone Bros.) <br /> on September 8, 2000 by the Central Valley Regional Water Quality Control Board (CVWB). <br /> Consistent with the California State Water Resources Control Board Resolution No. 2009-0042, and <br /> the letter dated July 8, 2009, from the CVWB, the groundwater monitoring frequency at the Site has <br /> been reduced to semi-annually, with monitoring occurring in the first and third quarters. Additionally, <br /> pursuant to requirements of the CAO, an update to the Site Conceptual Model (SCM) and the status <br /> of remediation activities are required semi-annually and quarterly, respectively, consistent with the <br /> deadlines established in the CVWB letter dated July 8, 2009. <br /> Gettler-Ryan Inc. (G-R)was contracted by CEMC to perform the groundwater monitoring and <br /> sampling for the Site. The semi-annual monitoring event was performed on August 27, 2010. The <br /> G-R field logs are included as Attachment A. <br /> Groundwater Level Measurements <br /> Groundwater depth was measured and recorded for the following groundwater monitoring wells on <br /> August 27, 2010: <br /> Hydrostratigraphic unit A/B—MW-1, MW-2, MW-3, MW-4, MW-5, MW-6, MW-7, MW-9R, <br /> MW-10, MW-10A, MW-11, MW-12, MW-13, MW-14, MW-14A, MW-15R, MW-16, MW-17, <br />