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10 August 2005 <br /> •1 AGE-NC Project No 99-0559 <br /> Page 7of8 <br /> I Installation of additional, shallow-to intermediate-depth ground water extraction wells on <br /> the southern and western margin of the site, in order to minimae the lateral migration of <br /> petroleum hydrocarbon-impacted ground water towards the south and west <br /> AGEro osed the off-site assessment of dissolved MTBE in the Site Assessment Work Plan <br /> p P <br /> Addendum dated 02 December 2003 The EHD letter dated 27 October 2004, provided comments <br /> on the scope of work and directed a work plan addendum The EHD comments specified the vertical <br /> definition of the dissolved contamination prior to additional off-site investigation "The workplan <br /> I does not address the vertical extent of the soil and groundwater contamination in the source area on- <br /> site" Additionally,the comments within the letter are somewhat contradictory in regards to sampling <br /> "off-site water sampling depth should not be preselected",while also stating the vertical assessment <br /> of dissolved contamination, on-site, would be required to "ensure establishing appropriate target <br /> sampling depth" AGE has generated a site conceptual model for the dissolved contamination based <br /> on site specific data, which was the basis for the Site Assessment Work Plan Addendum dated 02 <br /> December 2003 <br /> AGE prepared the Interim Soil Remediation and Additional Site Assessment Work Plan dated 25 <br /> INovember 2004 The EHD letter undated and sent by mail posed on 23 March 2005, provided <br /> ie comments on the scope of work in the work plan The EHD stated "The deep (180 feet bsg) <br /> groundwater sampling near CPT-2 in the identified unauthorized release area is acceptable,but the <br /> other 2 sampling location would be more beneficial if located closer to MW-5 and former CPT-4" <br /> and also requested Justification for the two other CPT locations AGE is not aware of a "source" <br /> located at well MW-5 and former CPT4 The location of well MW-5 and former CPT4 is <br />' hydraulicly down-gradient of the former UST locations and the sample collected from the well <br /> screens between 100 and 185 feet bsg were almost non-detect or had hydrocarbons detection at <br /> concentration below drinking water standards and therefore defines the vertical extent of the <br /> dissolved plume Establishing additional sampling points at well MW-5 and former CPT4 would not <br /> be more beneficial, the sampling would waste resources and duplicate ground water data <br /> unnecessarily <br /> The sampling proposed in the Interim Soil Remediation and Additional Site Assessment Work Plan <br /> is justified based on following site conditions the release of contamination was likely highest <br /> between wells MW-2 and MW-3 which represent the former UST excavation, the CPT location <br /> surround an area with regularly exhibited free-phase-product prior to the ground water extraction <br /> operation at the site,presenting the majority of the dissolved mass,and the highest concentration of <br /> MTBE and increasing BTEX compounds is at well MW-4 <br /> AGE recommends installation of additional CPT monitoring points at the former UST area as <br /> depicted in the Interim Soil Remediation and Additional Site Assessment Work Plan Additionally <br /> AGE recommends the installation of additional CPT monitoring points off-site as Site Assessment <br /> Advanced Geohnviroamentai,Inc <br />