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4 1 10 February 2006 AGE-NC Project No 02-0977 Page 11 of 12 5.0. RECOMMENDATIONS Based upon data collected during the fourth quarter 2005, AGE recommends • Continued utilization of wells MW-1 through MW-8 for quarterly ground water monitoring and sampling, the 1' quarter 2006 ground water monitoring event has tentatively been I scheduled for 22 March 2006 • In accordance with the SJCEHD directive letter dated 12 August 2005 for performance of two (2), separate batch removal events,the second of two ground water batch removal event was performed at well MW-2 between 23 and 27 January 2006, a report of findings is forthcoming ' • Soil and ground water data indicate that vapor phase migration may be occurring from the soil to the shallow ground water table Utilizing SVE wells VW-1 through VW-4, AGE recommends performance of an eight-hour SVE pilot study to evaluate SVE as a remedial ' alternative,the results of the SVE pilot test should provide data to calculate an effective SVE radius of influence for design of an interim SVE remediation system . An interim ground water remediation program should be implemented at the site as soon as possible to establish hydraulic controls and to inhibit further off-site migration of the MTBE-ground water plume AGE had previously proposed installation of a ground water I extraction well in the November 2004 Site Assessment Work Plan At a minimum, AGE recommends the installation of a ground water extraction well near well MW-2, implementation of an interim ground water extraction (pump-and-trat) remediation system utilizing carbon-based treatment with discharge into the City of Lodi sewer system, to mitigate the off-site migration of the dissolved MTBE towards MW-5 The State Water Resource Control Board document Guidelines For Investigation and Cleanup of MTBE and Other Ether-Based Oxygenates, dated 27 March 2000,recommends that"Removing MTBE from the subsurface at high concentrations is much more cost effective than extracting ground water or vapor with low concentrations" Further more,the documents states" aggressive Iinterim remediation in the source area can help to diminish the changes of creating a large dilute plume of MTBE" Current site conditions at the Flame Mini Martjustify active ground water remediation through ground water extraction Additional considerations j ustifying interim groundwater remediation at this site include (1) The high concentrations of contaminants (ie MTBE) encountered at the site that are significantly above the DHS's MCLs, (2) The high mobility of MTBE dissolved in the First Water Zone (54 to 65'feet), (3) the apparent migration (down-gradient) of the Flame Mini- Mart dissolved MTBE plume,at least 125 feet towards the south, as evidenced by increasing I MTBE concentrations at MW-5, and (4) successful pump-and-treat remediation results achieved from other nearby sites Advanced GeoEnvironmental,Inc 1