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Report of Findings—Dairy Waste Removal Page 6 Teixeira—Souza Dairy November 27,2006 WKA No.6504.07 The soil gas survey laboratory analytical results for methane are well below the screening level of 1,000 ppmv established in the Cal-EPA Department of Toxic Substances Control's (DTSC) June 2005 Advisory on Methane Assessment and Common Remedies at School Sites. DTSC-provided guidance documents regarding school sites are commonly applied to residential development, as both are considered "sensitive land-uses" by the DTSC. The soil gas survey data supports the conclusion that the visible waste was removed effectively. Soil gas concentrations in all areas could not be determined due to the impact from shallow groundwater and dense soils. Based on the results of the soil and groundwater samples collected during the preliminary investigation, the potential risks from hazardous gases appears to be low. However, since all areas could not be sampled due to shallow groundwater or dense soils, a soil gas assessment should performed in the areas identified as having the largest amounts of waste ifa building will be located in these areas. The assessment can consist of collecting soil gas data following backfilling and rough grading operations. Although general water quality parameters (nitrate,total dissolved solids) were not evaluated as part of the scope of the waste removal task, there is a potential that groundwater below the former dairy has been impacted. To determine whether the groundwater has been impacted and to support whether the groundwater concerns in the vicinity of the former dairy should be disclosed to future land owners as recommended by the RWQCB, an assessment of groundwater for general water quality paramenters should be conducted. Otherwise, a statement that y~ groundwater may be impacted from past dairy use should be disclosed to future land owners. Both the RWQCB and the San Joaquin County EMD have received closure documents for the dairy and have removed the dairy from the active confined animal facility list. To complete their files, a copy of this Report of Findings should be provided to the RWQCB and the San Joaquin County EMD. CLOSING The statements,conclusions, and recommendations in this Report of Findings are based upon the scope of work described above and on observations made on the dates of the applicable fieldwork. The work performed during the completion of this report was accomplished using a degree of skill