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CaliforniSegional Water Quality Cool l0oard <br /> Central Valley Region <br /> Arnold <br /> Linda S.Adams Schwarzenegger <br /> Secretaryfor Sacramento Main Office Governor <br /> rnvironmenral 11020 Sun Center Drive 0200.Rancho Cordova.California 956706114 <br /> Protection Phone(916)464-3291 •FAX(916)4644645 <br /> http://www.waterbouds.ca.gov/centralvalleyR�^E F=a <br /> 22 January 2007 f N \vV1 <br /> JAN 9, 4 2007 <br /> Mr. Dale Gillespie <br /> Geweke Land Development and Marketing ENPI RMITISE� " <br /> PACE <br /> PO Box 1210 <br /> Lodi, CA 95241 <br /> REPORT REVIEW, CLEANUP AND ABATEMENT ORDER (CAO) NO. 93-701, <br /> GEWEKE PROPERTY, 16 SOUTH CHEROKEE LANE, LODI, SAN JOAQUIN COUNTY <br /> I reviewed the 22 January 2007 Quarterly Report— Fourth Quarter 2006 (Report), submitted on your <br /> behalf by Advanced Geo Environmental, Inc. (AGE). The Report (see enclosed Figures 3 through 5) <br /> provides the analytical results from the groundwater monitoring event conducted 7 December 2006 at <br /> your site. Depth to water varied from 55 to 57 feet below ground surface. The downgradient <br /> groundwater direction was towards the south at a varying gradient of 0.001 ft/ft (onsite) to 0.003 ft/ft (off- <br /> site). Maximum groundwater concentrations were: Total Petroleum Hydrocarbons as gasoline, 300 ug/L <br /> in monitoring well MW-8, onsite and 1,800 ug/L in MW-9, off-site; and 1,2-dichloroethane (1,2-DCA) <br /> 12 ug/L in MW-9, offsite. All other analytical results for constituents of concern in groundwater are <br /> currently below Water Quality Objectives. The Report states the ozone injection system is increasing <br /> groundwater Oxidation Reduction Potential and Dissolved Oxygen levels, while concentrations of <br /> constituents of concern within the radius of influence of the ozone injection system have declined to non- <br /> detect levels. Monitoring wells MW-8 and MW-9 are outside of the radius of influence of the ozone <br /> injection system. AGE also conducted a Fate and Transport model (F&TM) utilizing the RISC <br /> Workbench 4 software, and evaluated vapor intrusion using the Region 2 Environmental Screening <br /> Levels (ESLs). The preliminary results of the F&TM show that petroleum hydrocarbons will not reach <br /> downgradient monitoring well MW-20. The ESLs comparison show that vapor intrusion will not occur <br /> into buildings from residual soil and groundwater concentrations. These findings are consistent with the <br /> quarterly monitoring, which shows the groundwater plume has stabilized and is currently shrinking in <br /> vertical and lateral extent. The Report recommends: <br /> Cessation of operation of the ozone injections system, <br /> Continued groundwater monitoring, and <br /> Consideration for site closure. <br /> I have the following comments on the Report: <br /> 1. 1 concur to cessation of operation of the ozone injection system for two quarters, to assess <br /> whether rebound of contaminant concentrations will occur. If concentrations remain non-detect <br /> after two quarters of monitoring, then permanent cessation of ozone injection will be appropriate. <br /> 2. By 30 March 2007, please provide an evaluation of additional In-Situ Chemical Oxidation <br /> technologies to address the residual petroleum hydrocarbons at MW-8 and MW-9, which are not <br /> amenable to ozone injection due to the low permeability of the soils. <br /> 3. Consideration for closure is not appropriate at this time, due to comments 1 and 2. However, <br /> you may wish to refine the F&TM, and calculate the amount of residual petroleum hydrocarbons <br /> California Environmental Protection Agency <br /> ped Recycled Paper <br />