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1 Quarterly Groundwater Report Frontier Transportation 0101-006 January 26, 2001 Page 4 MW-3. No detectable concentrations of the remaining oxygenates were identified from groundwater sample analysis of all eleven monitoring wells using EPA method 8260 (See ' Appendix B). 5.0) CONCLUSIONS AND RECOMMENDATIONS ' Based on groundwater sample analysis results, the dissolved TPH-d, TPH-g, TPH-m, BTEX, and MTBE plumes are spatially stable on-site and confined to the former UST location. ' No detectable concentrations of dissolved TPH-d, TPH-g, TPH-m, BTEX, and MTBE were identified in ten of the total eleven monitoring wells dedicated to the site. Dissolved TPH-d, TPH-g, TAH-m, BTEX, and MTBE were identified in monitoring well MW-3 exclusively located ' just east of former UST location. Attenuation of the above petroleum hydrocarbons has been identified in MW-3 since their respective recorded maximums. BEII also concludes that the purging of the groundwater at the site has removed a significant amount of dissolved petroleum hydrocarbons. Approximately 70 gallons of groundwater is purged from the site when all eleven groundwater wells are sampled. Since August 1996, approximately 600 gallons of groundwater have been removed from the site. The groundwater gradient is relatively flat (0.002 ft./ft.), therefore, the amount of groundwater purged ' has kept the plume contained to the site and decreasing in size. BEII recommends that quarterly groundwater monitoring continue at the site until constant or decreasing dissolved petroleum hydrocarbon concentrations are observed for a period ' of one year. At that time, BEII will request case closure for the site provided the above criteria is met. Groundwater samples will be analyzed for BTEX using EPA method 8020, TPH-d, TPH-g and TPH-m using EPA method 8015m, and oxygenates using EPA method 8260 in all future monitoring episodes as directed by the PHS/EHD. 1 1