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CLEARWATER <br /> C R O L P I . C <br /> Env,rottmesta! Seri ices <br /> 4.0 CONCLUSIONS AND RECOMMENDATIONS <br /> Results of the recent monitoring activities indicate that dissolved-phase contaminant concentrations <br /> and hydrogeologic conditions beneath the site are generally similar to those observed during <br /> pervious events It is anticipated that dissolved-phase contanunants concentrations will begin to <br /> decline with continued operation of the SVE/AS system <br /> Review of historical groundwater monitoring data suggests that a reduction in monitoring of some <br /> wells may be warranted Samples from wells MW-3 through MW-7 have essentially been free of <br /> detectable contaminant concentrations since installation Therefore, Clearwater recommends <br /> reducing the monitoring of these wells to an annual event However, Clearwater recommends <br /> continued quarterly monitoring of plume wells MW-1 and MW-2, and also the dorriestic well <br /> Monitoring of plume wells will provide ongoing data on the overall efficacy of the remediation <br /> system Historical sampling also indicates that MTBE is the only fuel oxygenate of concern at the <br /> site, therefore, Clearwater proposes to monitor this compound with EPA Method 8020 only The <br /> proposed groundwater monitoring schedule is summarized by the following table <br /> Well I D Quarterly Annually <br /> (1st, 2nd, 3rd, 4thQuarters) (1st Quarter) <br /> MW-1 DTW,TPRg,BTEX,MTBE <br /> MW-2 DTW,TPH ,BTEX,MTBE <br /> MW-3 DTW TPH ,BTEX,MTBE <br /> MW-4 DTW TPH ,BTEX,MTBE <br /> MW-5 DTW TPH ,BTEX MTBE <br />' MW-6 DTW TPH ,BTEX MTBE <br /> MW-7 DTW TPH ,BTEX,MTBE <br /> Domestic Well TPH ,BTEX,MTBE <br /> Notes, <br /> DTW=depth to water <br /> TPHg,BTEX,MTBE=by EPA Method 8015/8020(modified) <br /> The SVE/AS system is operating as designed, recovering gasoline hydrocarbons from the area of <br />' soil contamination at significant rates An estimated 3,437 lbs (563 gallons) of gasoline <br /> hydrocarbons have been recovered from the subsurface since remediation was initiated in October <br /> 1998 Clearwater recommends continued operation of the remediation system as it is currently <br /> configured until contaminant recovery rates fall off appreciably The Underground Storage Tank <br /> D-107 4Q98 GW & Sys Mon Report 6 January 27, 1999 <br />