SITE INFORMATION AND CORRESPONDENCE FILE 2

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17 August 2009 AGE-NC Project No. 96-0235 Page 2 of 3 AGE further believes that an in-situ method will be required to mitigate the contaminates to regulatory clean-up levels. round water extraction will not be effective in both cost and ins-lt/`w- performance, over the duration required to remediate the site�Based on the ground water aquifer, pumping test results,the feasibility of ground water extraction as a remediation option for removal of hydrocarbon-impacted ground water would requireoT excessive time, mainly due to lower than acceptable recoverable hydrocarbon concentrations with low ground water production quantities, and be limited in the removal of adsorbed hydrocarbons from the impacted soil below the water table.Additionally,the costs for monthly discharge connection,discharge and treatment equipment capital, reduces the efficiency of ground water extraction treatment. The in-situ methods include; the current ozone injection and the proposed air-sparging; additionally in-situ chemical oxidation ��'r ,,, );i.,* 17 with injection solid media (Regenox or other media)would be feasible for the site. While,dissolved methyl tertirary butyl ether(MTBE)concentrations have increased on-site in well MW-14B which is screened well below the target zone for the ozone injection; opposite has been the decline of the dissolved 1,2-dichloroethane (1,2-DCA) concentrations in the dee er well 4 \ MW-14B. The ozone injection pilot study design directed by the EHD, limite injections o upper water table and the ozone application was not anticipated for the mitigation of th per impacted hydrogeologic unit 2(HU2)near the northern UST release area.A limited number of ozone injection pOintswere approved bykhe EHD,while a total of ten ozone injection points were initially proposed. f Additional deep ozone sparge points should be installed to the depth of well MW-14B to remediate the deep dissolved MTBE and 1,2-DCA,prior to additional feasibility studies for other remediation methods As this stepped approach, would be most cost effective than alternative remediation r methods. Based upon the lack of detectable contaminants in shallow monitoring wells since March 2001,the dissolved plume release from the former UST#3 area appears to be isolated below the current water table, at a depth associated with a historical smear zone or historical low water level (MW-1 and MW-2).The vertical and lateral extent of the contamination is defined south of the UST#3 area and now well defined by the deep monitoring wells installed on the site and soil borings off-site south. The EHD is directing additional monitoring points to define areas which are already defined as non- 7 detect (MW-SAB) or is not accessible northeast of well MW-5/boring B15 is residential. Additionally,the EHD has concluded that installation of wells are required to define the deep ground water impact at well MW-14B. Almost two years ago,AGE proposed a well east of well MW-1. . It�d wky VL#t� The boring logs for the installation of wells EW-2 and IAS-1 are not available The report — documenting the well installation was submitted to the EHD, Quarterly Report - Third Quarter 2000, dated 29 December 2000. The report was recently reviewed by AGE and wells logs were not likely prepared within the report. The boring log for the second installation of well EW-1,near the location of well EW-1 within the former northern cluster area,was not reported.The boring log for well EW-1 is attached. The calculations for the mass of adsorbed hydrocarbons at former UST area #3 was presented in the Quarterly Report-October 1999 dated 17 December 1999 and are attached. Advanced GeoEnvlronmental,Inc.