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Mr. Marty Banned Project 803026 <br /> September8, 2000 <br /> Page 2 <br /> 6. Gmmdwatermmitoring program schedule and analytical requirements. <br /> ]. Implemcnatim schedule for Goal remedy and ongoing maintenance of the <br /> property. <br /> TECHNICAL RATIONALE FOR ELIMINATION OF GROUNDWATER <br /> EXTRACTION AND TREATMENT <br /> flumademacir extraction and treatment is a well documented remedial technology for <br /> hydraWie control of dissolved chemicals in groundwater. By comparison, g muds ater <br /> and treatment is also well documentd as beef Live mod costly in removing <br /> extraction <br /> chemical mass Gam groundwater. The decision to implement gmundwate <br /> extaetm and beatmmt at an impacted property, is primarily based m the need to <br /> prevent migration of a dissolved phase plume. The 601 East Miner Street groundwater <br /> quality data was reviewed to determine if plume migration wananlel implementation of <br /> geauedwater cnmciion and treatment <br /> The groundwater monitoring database was reviewed to determine the distributim of <br /> petroleum hydrocarbons in groundwater and to evaluate if the chemical mass may be . <br /> migrating from the site and potentially immcting downgradimt receptors. Table 1 <br /> sundepainzw <br /> widest levels; thickness of free-phase hydrocebm used concentrations of <br /> lesudeumhydrocmboas in groundwater samples collectd during groundwater <br /> pensioning events over the past six years. Figure I is a site plan showing the locations <br /> of gmmdwater monitoring wens and f comer andergromd storage anlm (USTs). to <br /> general, fuel hydrocebom have not bee duladled in gmuedwaler samples collected <br /> from downg eboad summoning wells mw-4 and mer 5. This indicates that the dissolved <br /> gromdwata plume cmmoating from the former USTs stable or declining in extent. In <br /> addition, the rauaining perimeter monitoring well, mw-6 has had consistently declining <br /> detectible concentrati um of gasolirno-ange total petroleum bydrocarbm (TPHG), <br /> bcuxene, toluene, Nsylbemenc, and xylnms (BTBX), and methyl tertiary-butyl ether <br /> (MTBfovathelastsksyeam. Together, the pecimetermonitoring well results indicate <br /> that the extent and magnitude of groundwater impact his reduced over the lust six years <br /> at the 601 east miner street facility. <br /> The groundwater monitoring database was Cumber reviewed to support the pervious <br /> conclusion. Monitoring Wells MW-1 and MW-3 were reviewed for Include trends. <br /> Data for these wells is sparse as compered to the perimeter m oriag wells. <br /> Nonetheless, similar hands were observed. For example, floating hydrocarbon is an <br /> longer observed in these wells. It must be noted that groundwater elevations have <br /> menaced such that the wells screens (or intakes) are now submerged; lheefose, cement <br /> IfloAvameron <br /> mwsumawamaiy=isvnswsozam..m.mvei <br />