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3.0 CONCLUSIONS, RECOMMENDATIONS AND PROJECT STATUS Since the groundwater surface was last measured in March 2001, groundwater levels dropped an average of 0 57 feet, the groundwater flow direction shifted approximately 10 degrees to the north, and the groundwater gradient remained relatively constant During the past four quarters of groundwater monitoring, the groundwater flow direction has remained north to northeast, at a relatively constant gradient ' Based on the results of previous subsurface investigation, soil and groundwater beneath the north end of the former middle UST are impacted by relatively low concentrations of gasoline ' hydrocarbons Most of the petroleum hydrocarbon mass remains concentrated in soil immediately below the north end of the former middle UST Vertically, the concentrations of gasoline hydrocarbons decrease rapidly with depth, and are defined between 65 and 80 feet bgs Based on the results from soil samples collected during the drilling of MW-1, MW-2 and MW-3, the lateral extent of impacted soil appears to be defined to the area of the former USTs ' Impacts to groundwater at the water table appear to be limited to low concentrations of MTBE in MW-3 The monitoring well network does not include a well north-northeast (downgradient) of the 10 former UST and dispenser system As such, the plume of impacted groundwater may not be fully delineated by the existing wells However, based on the low concentrations of gasoline hydrocarbons detected in groundwater beneath the site, it may be unnecessary to implement additional environmental corrective actions Based on these conclusions, Ramage Environmental recommends that PHSIEHD review the project data with RWQCB, and consider the case for regulatory closure Until the case is closed, ' groundwater should continue to be monitored and sampled on a quarterly basis, with the next event scheduled for September 2001 r • 11 I