SITE INFORMATION AND CORRESPONDENCE

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r Direct Contact and Outdoor Air Exposure Benzene and ethylbenzene concentrations in shallow soil samples (0 to 10 fbg) do not exceed the screening levels for direct contact and outdoor air exposure (for both the residential and commercial/industrial scenarios) and also do not exceed the screening level for the utility worker. 12.0 SUMMARY Based on the above information we have drawn the following conclusions about this site. • The release appears to have primarily occurred in the dispenser and associated product piping area. • The.primary COPC are MTBE and TBA in soil and MTBE, TBA, and 1,2-DCA in groundwater. • The horizontal extent of COPCs in soil and groundwater is adequately defined. • The current concentrations of MTBE in groundwater onsite are low (320 µg/L). Increasing TBA concentrations in the source area well suggest that MTBE is degrading. • The estimated MTBE mass remaining in soil is 1.5 pounds and in groundwater it is 15.3 pounds. • While no formal risk assessment has been conducted, exposure pathways do not appear to be complete beneath the site, and current conditions appear to represent a low-threat to human health and safety and the environment. • There are no known sensitive receptors in the site vicinity that have been impacted or are threatened by the COPCs remaining at this site. • Based on site conditions,the current best available remedial technology is monitored natural attenuation(MNA). • No further remedial activities appear warranted at this time. 13.0 RECOMMENDATIONS Based on the above site evaluation, CRA does not recommend further remedial activities,but recommends MNA as a final remedial approach at the site. Groundwater in wells MW-1 and MW-10 will continue to be monitored to evaluate MTBE concentration trends in these wells. If any significant changes are observed in the 247359(» 13 CONESTOGA-ROVERS&ASSOCIATES