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wl <br />California Regional Water Quality Control Board <br />n H. Hickox <br />Secretaryfor <br />Environmental <br />Protection <br />"[iI <br />Central Valley.Region <br />$te,ven T. Butler, Chair <br />Sacramento Main Office <br />Internet Address: http://www.swrcb.ca,gov/—rwgcb5 <br />3443 Routier Road, Suite A, Sacramento, California 95827-3003 <br />Phone (916) 255-3000 • FAx (916) 255-3015 <br />Gordon L. Boggs <br />UST Program Manager <br />Gray Davis <br />Governor <br />FROM: Marty Hartzell <br />Associate Engineering Geologist <br />DATE: 22 September 2000 SIGNATURE: "0—h ��_ <br />SUBJECT: REVIEW PROBLEM ASSESSMENT REPORT AND FINAL REMEDIATION <br />PLAN, FORMER CHEVRON STATION #9-5775,301 WEST KETTLEMAN LANE, <br />LODI, CLEANUP AND ABATEMENT (C&A) ORDER NO. 5-00-704 <br />I reviewed the 24 July 2000 Problem Assessment Report (PAR) and the 25 August 2000 Final <br />Remediation Plan (FRP) submitted by Secor International Incorporated (Secor) for the subject site. The <br />PAR and FRP provide a summary of site soil and groundwater investigation activities and results, and a <br />proposed strategy to remediate soil and groundwater contamination. However, these reports do not <br />present a complete assessment of site contamination, and do not show that the groundwater plume is <br />being stabilized as required by the C&A Order. Specific discrepancies with the PAR and FRP are <br />discussed as follows: <br />40 Soil contamination is shown to extend below the former underground storage tanks (USTs) to 72 feet at <br />soil boring SB -1. Low concentrations of benzene and MtBE were identified at this maximum depth; <br />therefore, the vertical extent of soil contamination has not been defined on-site. Groundwater <br />contamination is shown in the shallow and deep monitoring wells on-site and extends from the former <br />UST area south across Kettleman Lane into the shopping center parking lot (see enclosed Figures 1 and <br />2 from the FRP). As shown on Figures 1 and 2, the extent of groundwater contamination has not been <br />defined north of the former UST area, and south of MW -10. <br />Secor installed multiple monitoring wells both on-site and off-site in June 2000 to delineate the extent of <br />groundwater contamination, and to provide a sentinel well between the on-site contamination and the <br />City of Lodi Municipal Well 12 (Well 12) approximately 500 feet southwest of the site. The sentinel <br />well, MW -8B, was screened in silty clay from 85 to 90 feet, which is inappropriate. As shown in the <br />PAR and FRP, MW -8B is downgradient from the site, approximately 200 feet from the former USTs, <br />and has been non -detect for all constituents sampled on 12 July and 24 July. Water levels from this well <br />measured on 12 July and 24 July were shallower than surrounding deep zone wells and could not be used <br />for contouring. In comparison, MW -10B was completed in clayey silt from 85 to 90 feet, with silty sand <br />above. MW -10B is cross gradient approximately 300 feet from the former USTs, and has shown low <br />MtBE contamination in the 12 July and 24 July sampling events. Therefore, MW -8B is not. screened <br />appropriately to serve as a sentinel well for Well 12, and must be replaced. Prior to installing another <br />well in this area, Chevron must complete continuous core data collection (e.g. cone penetrometer testing) <br />with discrete groundwater sampling to identify permeable aquifer units. <br />As directed in C&A Order #3, Chevron is to "Install and continuously p vapor operate a soil or extraction <br />p <br />system, and an interim pump and treat system in the area of the highest soil and groundwater MtBE <br />California Environmental Protection Agency <br />01 Recycled Paper <br />