SITE INFORMATION AND CORRESPONDENCE

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s ` • 9 24 June 2011 Ms. Kehler and Mr. Betker Page 2 of 2 JM Equipment 1245 W. Charter Way, Stockton hydrocarbon concentrations and/or stimulate the level of bacterial activity to further reduce hydrocarbon concentrations. The approved wells designs are as follows: • Four LDBs will be advanced to a depth of 25 feet below surface grade (bsg) using 18- inch hollow-stem augers, two of which will be completed with 6-inch diameter PVC casings with screened intervals between 15 and 25 feet bsg, one will be completed with a 4-inch PVC casing also screened between 15 and 25 feet bsg, the fourth boring will be completed with 2-inch PVC casing screened between 23 and 35 feet bsg with filter pack between 13 and 25 feet bsg. These wells will have the designation IW. • Three 8-inch diameter borings will be advanced for conversion to observation wells down-gradient of the IW wells; these wells will be constructed with 2-inch PVC casing screened between 15 and 25 feet bsg, and will have the designation OW One 6-inch IW will be utilized for testing ORC socks, the other will be used as a control well which will not have any oxygen compounds injected. The 4-inch well will be utilized for injection of hydrogen peroxide and the 2-inch well for air sparging. The OWs and monitoring well MW-5 will be utilized to monitor the effects down-gradient of the IWs. A soil sample will be collected from each boring between 20 and 20.5 feet bsg for sample description and laboratory analysis for various petroleum hydrocarbons and metals that potentially may be mobilized by the injection of oxygen or oxygen compounds. The EHD approves the analyses for the hydrocarbons, but suggests that metals analyses be performed on composited samples to minimize analytical costs. The EHD also approves the analysis of groundwater samples collected monthly (during the feasibility tests) from the OWs for the proposed hydrocarbons, but recommends limiting the metals analyses to the extent possible consistent with the monitoring requirements of the Central Valley Regional Water Quality Control Board for their General Permit evaluation and with the evaluation goals of this feasibility study. The study is proposed to be conducted for one year, however if the results clearly demonstrate a preferred injectant in a shorter time period, the test period may be shorted to save expenses and accelerate effective remediation. If appropriate, for the same reasons the report of findings for this investigation may be submitted as part of a revised RAP for the site. Thank you for your cooperation in continuing your corrective actions at the site. Questions and comments may be directed to Michael Infurna, at (209)468-3454, or to Nuel Henderson at (209) 468-33443p6.. / Nuel C. Henderson Jr., PG Engineering Geologist c: Mr. James L. Barton, CVRWQCB Mr. Mark Owens, SWRCB Ms. Tamorah Bryant, Geological Technics Inc., 1101 7th St., Modesto, CA 95354 1245 W Charter RAP addn CML 6-24-11.doc