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CLEARWATER G a 0 L P 1 \ C Ell nt¢! Sr.riccs a9+ y- 4.0 CONCLUSIONS ANIS RECOMMENDATIONS Results of recent groundwater monitoring indicate that the SVEIAS system continues to have a significant effect on ' reducing dissolved-phase contaminant concentrations beneath the site Dissolved-phase contaminant concentrations for the plume are down approximately two orders of magnitude since the fourth quarter 1998 A continued decline in these ' concentrations is expected with the ongoing operation of the SVEIAS system throughout the summer The wells will continue to be monitored in accordance with the schedule previously recommended Well I D Quarterly Annually (1st, 2nd, 3rd, 4thQuarters) (1st-Quarter) MW-L DTW TPH¢ BTEX MTBE MW-2 DTW TPHg BTEX MTBE MW-3 DTW TPHg BTEX MTBE MW-4 171vJ TPlig BTEX MTBE MW-5 DTW TPHa BTEX MTBE MW-6 DTW TPHg BTEX MTBE MW-7 EnW TPHE BTEX MTBE Domestic Well TPtig BTEX MTBE Notes. DTW=depth to water TPHg BTEX MTBE=by EPA Method 8015/8020(modified) lie The SVE/AS system is operating as designed, recovering gasoline hydrocarbons from the area of soil contamination at significant rates An estimated 7,344 lbs (1,204 gal)of gasoline h}drocarbons have been recovered from the subsurface since remediation was initiated in October 1998 However, contaminant influent concentrations !a3 and recovery have begun to drop off over the last quarter, indicating that the system has successfully removed as much contamination as possible Clearwater recommends continued operation of the remediation system as it is currently configured through the end of third quarter 1999, at which point it is anticipated that contaminant recovery will be negligible If this occurs, it is anticipated that the system will be shut-down at that time 1 • D-107 2Q99 GW&Sys Mon Report 5 July 21 1999