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CLEARWATER <br /> I G R O U P I N C <br /> Enpironmer:nal Serwccs <br /> 4.0 CONCLUSIONS AND RECOMMENDATIONS <br />' Results of recent groundwater monitoring indicate that the SVE/AS system has had a significant effect on <br /> dissolved-phase contaminant concentrations beneath the site Dissolved-phase contaminant concentrations are <br /> down approximately one magnitude over the previous results A continued decline in these concentrations is <br />' expected with the ongoing operation of the SVFJAS system throughout the summer The most important wells to <br /> monitor for the effect of site clean-up, in addition to the domestic well, are plume wells MW-1 and MW-2 <br /> Perimeter wells have been essentially free of contamination since installation and quarterly monitoring of these <br /> wells is not warranted Therefore,Clearwater intends to continue groundwater monitoring in accordance with the <br /> following schedule,as proposed earlier in Clearwater's Groundwater and System Operation Monitoring Report- <br /> Fourth Quarter 1998 dated January 27, 1999 <br /> Well I D Quarterly Annually <br /> (1st 2nd, 3rd, 4thQuarters) (1stQuarter) <br /> MW-1 DTW TPHg BTEX MTBE <br /> MW-2 DTW TPHz--BTEX MTBD <br /> MW-3 Urw TPHg 13TEX_MTBE <br /> MW-4 Mw TPHg--BTEX MTBE <br /> MW-5 DTW TPHgBTEX,MTBE <br /> MW-6 MW _ rPHg BTEX,MTBE <br /> �1W 7 - I3TN <br /> T TBh MTBE <br /> lie <br /> I <br /> Domestic Nell TPHa STG?! M'LEE <br />' to <br /> DTW=depth to water <br /> TPHg,BTEX MTBE=b) EPA Method 8015/81120(modified) <br />' The SVE/AS system is operating as designed, recovering gasoline hydrocarbons from the area of soil <br /> contamination at significant rates An estimated 6,287 lbs (1,031 gal) of gasoline hydrocarbons have been <br />' recovered from the subsurface since remediation was initiated in October 1998 Clearwater recommends <br /> continued operation of the remediation system as it iS currently configured until contaminant iecovery rates fail <br /> off appreciably <br /> The Underground Storage Tank Clean-up Fund has approved the costs for ongoing groundwater monitoring <br />' through 1999 and SVE/AS system operation through the end of September 1999 It is anticipated that system <br /> operation beyond that time will not be likely, as lower water tables and dry soil conditions of summer will be <br />' }deal for the final stages of S VE/AS system opei ation <br /> • <br /> 1 <br /> D-107 1Q99 GW&Sys Mein Report 5 April 5, 1999 <br />