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California Regional Water Quality Control Board eg?;Central Valley Region <br /> Robert Schneider,Chair <br /> Winston H.Hickox Gray Davis <br /> Secretaryfor Sacramento Main Office Governor <br /> Environmental Intemet Address: http://www.swrcb.ca.gov/—mgcb5 _O <br /> Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 <br /> Phone(916)255-3000•FAX(916)255-3015 a _ <br /> 6 August 2001 �^ <br /> v <br /> Nick Nickerson Phil Delk Jay Allen = <br /> Unocal DBG/AMG Deputy General Counsel Stone Brothers N <br /> 8788 Elk Grove Blvd. Montgomery Wards Management C9Ahpany_,- <br /> Building 3, Suite 15 535 West Chicago Avenue 1024 W. Robinhood Dr <br /> n Elk Grove, CA 95624 Chicago, IL 60671 Stockton, CA 95207 <br /> RE VIEWREMEDIA TION PLAN, FORMER UNOCAL STATION#5098, 5606 PA CIFIC A VENUE, <br /> ^ STOC%TON, SAN JOA QUIN COUNTY, CLEANUP AND ABATEMENT ORDER (C&A) NO. 5-00-707 <br /> Staff reviewed the 10 July 2001 Remediation Plan, Former Unocal Site (Remediation Plan) <br /> submitted by Environmental Audit, Incorporated(EAI). The Remediation Plan presents a plan of <br /> work to remediate soil and groundwater contamination associated with the former Unocal Station <br /> #5098 (Unocal) and the former Montgomery Wards Auto Service (Wards) sites. Implementation of <br /> the Remediation Plan will meet the requirements of Item No.10 in C&A No. 5-00-707 to construct <br /> and operate a remedial system. <br /> EAI evaluated multiple remedial alternatives in their 13 October 2000 Supplemental Investigation <br /> Report, Problem Assessment Report and Workplan, and identified soil vapor extraction (SVE) <br /> combined with air sparging(AS) as an effective alternative. EAI also identified biosparging as an <br /> alternative to enhance aerobic biodegradation of dissolved hydrocarbons. EAI noted that SVE/AS <br /> was implemented at the Wards site, and has proven to be efficient in remediating dissolved <br /> groundwater contamination. <br /> As outlined in the Remediation Plan, EAI proposes to complete the following supplemental <br /> assessment and remediation work: <br /> 1. Advance two cone penetrometer testing(CPT) borings (one at the Unocal site, and one at the <br /> Wards site) to a minimum depth of 150 feet to determine lithology comparable to borings <br /> completed on the Delta College property in November 2000. <br /> 2. Install two monitoring wells on the Wards property to monitor intermediate and deep zone <br /> contamination. The proposed screen intervals are 85 to 90 feet, and 100 to 105 feet; <br /> however,the exact screen zone intervals will be determined based on drilling data. <br /> 3. Install an air sparge well on the former Unocal site, and a biosparge well on the Delta College <br /> property. The proposed screen intervals are 65 to 70 feet. <br /> California Environmental Protection Agency <br /> ea Recycled Paper <br /> The energy challenge facing California is real.-Every Californian needs to take immediate action to reduce energy consumption. For a list of simple <br /> ways you can reduce demand and cut your energy costs,see our Web-site at http://www.swrcb.ca.gov/mgcb5 <br />