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Report of Findings—Phase 11 Soil anu--iroundlvater Assessment Page 9 Teixeira-Souza Dairy February 1,2007 WKA No.6504.45 On June 21, 2006, Lawrence Livermore National Laboratory(LLNL) completed a regional nitrate study to identify the sources of nitrate in the Central Valley groundwater supply. The study concluded that, "[groundwater] contamination due to animal waste (including seepage from septic systems) has decreased over the past two decades, and that synthetic fertilizer is increasing as a source of nitrate contamination in the Valley's groundwater." The study also concluded that naturally occurring nitrogen in soil is the most likely source of high background levels of nitrate in basin groundwater. WKA is currently attempting to obtain the results of this study to evaluate the range of background nitrate levels in California's Central Valley that were identified in the LLNL study. Summary The results of this assessment have identified the presence and distribution of impacts to soil and groundwater that may be attributable to previous on-site dairy operations. Although there is currently a lack of defined regulatory enforceable cleanup goals for dairy demolition activities, waste removal activities previously documented by WKA generally meet with current regulatory agency recommendations for dairy closures. Due to the ever increasing awareness of potential long term liabilities associated with residual dairy-related impacts to soil and groundwater, additional mitigation measures could be implemented to minimize the potential for future exposure to residual impacts to soil and groundwater quality. These measures could include posting a deed restriction on future groundwater use at the property and the development of a storm-water management plan (until the land is developed). Based on the results of assessment activities completed to date, it is recommended that future earthmoving activities conducted on the site should be observed for indications of previously unidentified dairy waste, carcasses, or impacted soil related to previous dairy operations. Depending on the intended future use of selected areas of the site as compared to previous dairy operations, an additional assessment of soil, groundwater, and possibly soil-gas may be recommended in those areas following backfilling and rough grading operations. As part of evaluating future land use, a sensitivity receptor survey and human health risk assessment would also provide better clarity as to the potential long term exposure risks associated with soil and groundwater conditions. WKA does not make land use decisions; therefore this Report of Findings should be used by land use attorneys to make any finals decisions regarding disclosure. 'N\ ��\