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1 • aEc�Eo�� <br /> 1 EMM. <br /> APR - d 2005 ENSR International <br /> 10411 Old Placerville Road <br /> March 31, 2005 ENVIRONMENT HEALTH Suite 210 <br /> 1 PERMIT/SERVICES Sacramento,CA 95827-2508 <br /> (916)362-7100 <br /> FAX (916) 362-8100 <br /> Mr. James Barton www.ensr.com <br /> 1 California Regional Water Quality Control Board <br /> Central Valley Region <br /> 11020 Sun Center Drive, Suite 200 <br /> 1 Rancho Cordova, CA 95670 <br /> 1 RE: Amendments to Monitoring and Reporting Program CAO No. 5-00-707 and Work <br /> Plan to Install an Additional Air Sparge Well within the Deeper Aquifer Zone (near <br /> MW-3) and Convert Monitoring Well MW-23S into an Air Sparge Well <br /> 1 Former Unocal Facility No. 5098 <br /> 5400 and 5606 Pacific Avenue, Stockton, California <br /> 1 Dear Mr. Barton: <br /> On behalf of Union Oil Company of California (Unocal), ENSR Corporation (ENSR) has <br /> 1 prepared this work plan for additional air sparge well installation and proposed changes to the <br /> Cleanup and Abatement Order (CAO) No. 5-00-707 issued to a Montgomery Ward, LLC <br /> (Wards), Unocal, Surry California Limited Partnership, and Stone Brothers and Associated <br /> 1 General Partnership (Stone Bros.) on September 8, 2000, by the California Regional Water <br /> Quality Control Board, Central Valley Region (RWQCB) (Section 1.1.5) for the Former Unocal <br /> Station No. 5098 at 5606 Pacific Avenue, and Former Montgomery Wards (Wards) Auto <br /> 1 Service located at 5400 Pacific Avenue, Stockton California. The location of the site is shown <br /> in Figure 1 and site features are illustrated on Figure 2. The California Regional Water Quality <br /> 1 Control Board, Central Valley Region (RWQCB) requested this work plan in a letter dated <br /> February 23, 2005. A copy of the RWQCB letter is included as Attachment A. <br /> 1 Wards and Unocal are named jointly responsible for actions necessary to abate the effects of <br /> contamination in the vicinity of the sites. In August 2000 Wards and Unocal executed an <br /> 1 agreement for Coordinated Corrective Action for Underground Storage Tank (UST) Fund Claim <br /> No. 1760 and UST Fund Claim No. 6864. On November 2, 2001, Unocal was named as the <br /> Appointed Representative for the PACIFIC/ROBINHOOD COMMINGLED PLUME. In this work <br /> 1 plan, reference to the "site' includes the former Wards and Unocal sites. <br /> Air Sparge Well Installation <br /> 1 In order to more effectively remediate dissolved concentrations of petroleum hydrocarbons in <br /> groundwater in the area of Robinhood Drive, ENSR proposes to install one new air sparge well <br /> 1 and convert an existing monitoring well—MW-23S—into a sparge well. Both the new and <br /> 1 J:1Pmlects10694015098-2931Working\Repons15098 Work Plan 2AS wells.doc <br />