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GROUNDWATER ASSESSMENT REPORT VI. CONCLUSIONS - SOIL AND GROUNDWATER ASSESSMENTS Soil analysis and field observations during the April 7, 2000 UST removal indicated minor residual contamination of petroleum hydrocarbons remaining beneath the former tank ESA's subsurface soil and groundwater_investigation_on July 5, 2000 indicated that a very low MTBE _ concentration (I lAgIL) in soil was localized at the north end of the former UST excavation MTBE was not detected in soil samples collected east or west of the excavation perimeter, or from beneath the center of the former UST excavation Groundwater samples collected July 5, 2002 investigation only detected MTBE at the north (1,300µglL)and south(14 tig/L)ends of the former UST MTBE was not detected in groundwater collected immediately down-gradient from the souther portion of the tank, indicating the groundwater impact is localized within the area of the-UST-excavation_Analyses did not detect MTBE above the laboratory reporting limits-in groundwater samples collected east and west of the UST excavation further indicating the confined extent of impacted groundwater ' Results of the January 2001 investigation confirm that the slight impact to shallow groundwater appears localized Laboratory analyses did not detect MTBE in groundwater samples collected from around the former UST,indicating that MTBE has not migrated laterally or vertically In addition, detected lead concentrations in soil are low, representative of naturally occurring background levels , The only chemical constituent detected over four quarters of groundwater monitoring was 15 /ig/L of MTBE detected in groundwater monitoring well MW-3 in January 2002 Groundwater analysis in the three subsequent monitoring rounds did not detect MTBE in MW-3 Monitoring well MW-3 is located at the north end of the former UST and groundwater monitoring results indicate that that MTBE has not migrated laterally or vertically Given the underlying geology ' and hydrogeologic conditions discussed in the previous sections, the detection of a one time low concentration of MTBE is not expected to represent a threat to public water supplies or surface water bodies VII. RECOMMENDATIONS , Considering the minimal impact of MTBE to the soil and groundwater and its localized extent confined to the UST excavation, it is ESA's opinion that the conditions at site are not significantly impacting soil and groundwater, and therefore requests that this case be granted a "No Further Action" status and case closure - _ ESA has formulated this reconumndatian based on the conclusions, as summarized below, that _ have been developed from the findings of the UST removal in Apn12000,and subsurface assessment peiforimed in July 2000 and January 2001and four quarters of groundwater monitoring by ESA Information required in the Tri-Regional Checklist of Required Data for No Further - Action Requests at Underground Tank Sites is provided in Appendix F ' A mass of MTBE-impacted soil was not identified through soil sampling and analysis Residual concentrations localized near the former UST excavation do not represent a significant mass capable of migrating vertically downward through the soil Groundwater Assessment Report 25 FSA 1200252 ' September 2003