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u A S S O C I A T E S I N C ■ hydrocarbons Therefore, the likelihood of pollutants remaining in the aquifer threatening these potential receptors is expected to be very low Criterion 4: The total pollutant mass remaining in the groundwater is decreasing at predicted rates and neither creates, nor threatens to create, a risk to human health and safety or future beneficial use(s) of the aquifer. ' During the last monitoring event only TPHg, ethyl benzene, and xylenes were present in the groundwater from well MW2, all other constituents were reduced to nondetectable levels The concentrations of ethyl benzene and xylenes are below their respective ' Department of Water Resources Maximum Contaminant Levels (MCLS) for drinking water Based on depth to groundwater, limited extent of impacted soil and groundwater, and distance to receptors, the subject site does not appear to represent a significant risk to human health and the environment Human exposure to residual petroleum affected soil is unlikely unless excavation of the soil were to occur Human exposure to the dissolved groundwater plume is unlikely unless an on-site shallow well in the immediate vicinity of the former USTs is used for drinking water purposes 7.2 Appendix B Check List ' Appendix B of the Tri -Regional Board's recommendations checklist of required data for site closure of USTs has been completed, as appropriate The checklist is included in this report as ' Appendix A 8.4 CONCLUSIONSIRECOMMENDATIONS Findings of our evaluation concluded that the project site does not appear to represent a significant risk to human health and the environment Based on the available data, on behalf of ' Ripon Unified School District, ATC formally requests NFA for this site ATC recommends destroying existing monitoring wells MW1 through MW5 Upon concurrence ' by SJCEHD with our recommendations, ATC will submit a workplan and permits for monitoring well destruction w 11309%reportslolosure doc 10