SITE INFORMATION AND CORRESPONDENCE_FILE 1

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U-Haul page 2 2701 N. Wilson Way, Stockton Although U-Haul and Harry's Auto at 2662 N. Wilson are both working cooperatively with EHD and the impacted well site, Frontier Motel, to provide a safe drinking water supply, the pathway(s) and potential for 1,2-DCA to further impact the well are not defined and require your immediate attention. EHD cannot approve a final remedial action plan at this time, but can evaluate and allow interim remedial action to occur. An interim action is any action necessary to abate or correct the actual or potential effects of an unauthorized release. Some examples are listed in the California State UST Regulations (Title 23, Division 3, Chapter 16, Article 11, sec 2722). An interim action can be conducted concurrently with any phase of corrective action or investigative work. EHD will require you to evaluate the need for interim action and include your findings in the next work plan submitted. You are hereby directed to submit a work plan for the continued investigation of the lateral and vertical extents of the UST release(s). 1,2-DCA, as well as the other oxygenates, should be included with the required TPHg and BTEX. Soluble lead and EDB analyses should be included for selected samples to support conclusions that these additives are not present in the soil and groundwater. Conclusions for the absence of LUFT waste oil constituents should also be supported by soil and groundwater data. The work plan is due by July 14, 2003. Only analyses data from soil samples that indicate petroleum constituents are not present at LUFT detection limits for two consecutive five-foot samples can be considered as support for conclusions for vertical delineation. Data from all previous soil sampling that cannot support vertical delineation with non-detect results should have additional soil samples collected from those areas and analyzed for all petroleum constituents of concern. Groundwater contamination has been detected in the deepest monitoring wells so the contamination is not vertically defined. Groundwater contamination has been detected in the lateral monitoring wells so the contamination is not laterally or vertically defined. Additional lateral shallow and deep monitoring wells must be installed. To aid in EHD's review of the work plan, justify each element of the work plan in the context of a Site Conceptual Model (SCM) constructed from the available data for the site.