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t.. G�olagrcal%dmics Inc. Page 5 City of Escalon Soil&Groundwater Report Project No. 750.2 March 15, 1999 HP-5, only 30 feet from HP-1, contained low levels of BTEX and moderate to low levels of MTBE and TBA. Once the contaminant reached groundwater, it spread out laterally, impacting the groundwater at HP-1, HP-2, HP-4 & HP-5. From review of the groundwater analytical data there does not appear to be a preferential spread of the groundwater plume in one direction as a result of a groundwater gradient direction. With HP-3 & 6 non-detect, it appears that the groundwater plume may not be very large. 4.0 CONCLUSIONS & RECOMMENDATIONS Conclusions 1. The majority of mass of soil contamination is localized around HP-1 in the upper 20 to 25 �. feet of soil. 2. Elevated concentrations of MTBE and TBA are present at the site. 3. BTEX, TPH-G and MTBE have impacted groundwater at low concentrations. 4. Groundwater was at 60-61 feet bgs during the February site investigation. �. 5. Groundwater gradient is unknown for the site. Recommendations To provide protection from further degradation of groundwater by these contaminants, the following recommendation is made. - 1. The soil should be excavated down to a depth of approximately 20 to 25 feet in the @. %woo vicinity of HP-1. This would remove the largest mass of contamination that otherwise would continue to leach into the groundwater. 2. Due to limited space at this site, the excavated soil should be pre-qualified for disposal at Forward Landfill and transported there immediately. if this is not possible, then an area for stockpiling the excavated soil should be investigated. 3. Confirmation samples and air quality monitoring samples should be collected during the excavation and a closure report prepared. This report should include: • calculations of the estimated mass of contaminants removed • calculations of the mass of residual chemicals in the soil and groundwater • evaluation of the need for additional groundwater investigation and evaluation of risk the residual chemicals pose to public health of the environment. 5.0 LIMITATIONS This report was prepared in accordance with the accepted standards and practices of the field of environmental geology, groundwater hydrology and good business practices. It should be recognized that definition and evaluation of environmental conditions is a difficult and inexact science. Judgments leading to conclusions and recommendations are generally made with an incomplete knowledge of the site-specific conditions present. The tasks proposed and completed during this project were reviewed and approved by the local regulatory agency for compliance with the law. No warranty, expressed or implied, is made.