SITE INFORMATION AND CORRESPONDENCE_2

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v �. r Del Monte Disco 110 N. Filbert St., Stockton. page 2 As an alternative to the bench test, EHD will allow you to install, test, and operate a limited Ozone Sparging System (OSS) as an interim action. By installing and operating a limited OSS now as an interim remedial action, you would be able to actually test the effectiveness of this remedial alternative and modify the final remedial plan based on 'hard' data. Additionally, an effective interim action could mitigate some of the impact of 1,2-DCA to the groundwater during the test phase and may only require a few additional wells to be installed later and connected to the already operating OSS. As an interim remedial action, an OSS may be operated for up to six months before a report that details the results and support for its continued use are submitted to EHD for evaluation. It is hoped that this approach would provide for an even quicker mitigative action to an already impacted aquifer, reduce the down-gradient plume size, and shorten the overall remediation program for the site. The inclusion of this recommended approach into your Pilot Test Work Plan would require only a slight modification of the work plan and EHD offers the following for you evaluation. The number of wells installed on the 'eastbound' Highway 4 on-ramp should be reduced from the five wells as originally proposed in a meeting with Del Monte and EHD on April 17, 2002. The number of wells installed during this interim phase should be just enough to demonstrate the area of influence hypothesized and should be constructed in a manner that will not allow for 'short-circuiting' of injected air or ozone to the extraction well installed in the same boring ('nested'). This effective area of influence may be reduced if the two inch (2") extraction well casing placed directly above multiple sparge casings were to 'short-circuit' the rising air/ozone. The natural outward and upward flow could be disturbed and the area of influence would be reduced. With the need to achieve and maintain the natural upward and divergent migration of the injected air/ozone for maximum effectiveness as discussed in the work plan, EHD is concerned that placing the extraction well casing in the same bore hole as the two injection casings may short circuit the natural flow of the injected air/ozone. As previously proposed, the nested ozone sparge wells/extraction wells would be approximately 100 feet apart and would be expected to have over-lapping equal areas of influence of at least 50' each, if not more.