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Ewm. <br /> I ENSR International <br /> 10411 Old Placerville Road <br /> D210 <br /> {D E C F�WESuite <br />' w Sacramento,CA 95827-2508508 <br /> July 27, 2005 (916)362-7100 <br /> JUL 2 9 2005 FAX (916)362-8100 <br />' www ensr com <br /> ENVIRONPOENT HEALTH <br /> Mr ,lames L Barton PERMIT/SERVICES <br /> Central Valley Water Board <br /> 11020 Sun Center Drive, Suite 200 <br /> Rancho Cordova, CA 95670-6114 <br />' RE: Updated Site Conceptual Model, Quarterly Monitoring and Remediation Status Report <br /> Second Quarter 2005 <br />' Former Unocal Facility No. 5098 <br /> 5400 and 5606 Pacific Avenue, Stockton, California <br />' Dear Mr Barton <br /> ENSR Corporation (ENSR) has been authorized by Union Oil Company of California (Unocal) to <br /> prepare an updated Site Conceptual Model (SCM) and a Second Quarter 2005 Groundwater <br /> Monitoring and Remediation Status Report for the above-referenced site Former site facilities <br /> that are the subject of this report were located both at the former Montgomery Ward, LLC <br /> a s (Wards) site located at 5400 Pacific Avenue and at the former Unocal site located at <br /> 5606 Pacific Avenue, Stockton, California (Figure 1) Groundwater monitoring has been <br /> conducted pursuant to requirements of Cleanup and Abatement Order (CAO) No 5-00-707, <br /> issued to Wards, Unocal, Surry California Limited Partnership, and Stone Brothers and <br /> Associated General Partnership (Stone Bros ) on September 8, 2000, by the California Regional <br />' Water Quality Control Board, Central Valley Region (RWQCB) (Section 1 1 5) The work <br /> reported in this document was performed in accordance with the field methods and procedures <br /> Included in Attachment A The locations of former and current site features are illustrated on <br /> Figure 2 <br />' Groundwater Level Measurements <br /> Depth to groundwater measurements were recorded for onsite and offsite monitoring wells on <br /> April 11, 2005 Four water-bearing zones have been identified beneath the subject site and <br />■ vicinity Unit A, Unit B, Unit C and Unit D This nomenclature was developed by Environmental <br /> Resolutions, Inc (ERI) and is based on site conditions presented in ERI's Work Plan for <br /> Supplemental Environmental Investigation report dated November 12, 1998 Unit A wells include <br /> MW-10A, MW-14A, MW-18, MW-19S, MW-21S, MW-22S, and MW-25S which are screened from <br /> approximately 30 to 50 feet below ground surface (bgs) Unit B wells Include MW-1 through <br /> MW-7, MW-9R, MW-10 through MW-17, MW-18D, MW-19D, MW-21D, MW-22D, MW-25D, <br /> AS-26, and MW-27 through MW-30 which are screened from approximately 50 to 70 feet bgs <br /> Unit C wells include MW-23S, MW-24S, and MW-31 and are screened from approximately 85 to <br /> Q Celebrating 35 Years of Excellence in Environmental Services <br />