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` DAMES MOORE APROFFS5K)NALLIM I l 1:1I 1 P.K I'VRi>HiF <br /> ATTACHMENT <br /> CHRONOLOGY OF SITE INVESTIGATIONS <br /> FORMER AFPC SITE <br /> 2801 WEST LANE, STOCKTON, CALIFORNIA <br /> o February 1986- Bechtel National conducted soil assessment <br /> which included the installation of three soil borings around <br /> the tank. A total of 10 soil samples were analyzed for <br /> total petroleum hydrocarbons (TPA) as diesel . Sampling depth <br /> extended to 27 feet below the surface. <br /> o June-September 1987- Kleinfelder conducted a soil and <br /> groundwater assessment in the vicinity of the diesel tank <br /> which included the installation of 33 soil borings around <br /> the maintenance shop. A total of 75 soil samples were <br /> submitted for chemical analysis. Depths of the borings ranged <br /> from 24 to 35 feet below the surface. Investigation also <br /> included the installation of three monitoring wells. <br /> Wells were installed outside of the soil contamination area <br /> to avoid creating potential conduit for diesel to migrate to <br /> groundwater. Sampled and analyzed groundwater for TPH, <br /> volatile aromatic hydrocarbons, phenols and polynuclear <br /> aromatic hydrocarbons (PAH' s) . No compounds were detected. <br /> o April 13 1988- Dames & Moore submitted work plan for soil <br /> investigation to San Joaquin Local Health District. <br /> o April 29 1988- Ms. Diane Henson of San Joaquin Health <br /> District verbally approved work plan. <br /> o May 2 , 1988- San Joaquin County submits written approval of <br /> Dames & Moore' s work plan. <br /> o May 3 , 1988- Dames & Moore began soil investigation which <br /> consisted of the installation of 18 additional soil borings <br /> and the analysis of 103 soil samples. <br /> o June 13-15 - Dames & Moore collected and analyzed <br /> groundwater samples from existing wells. Samples were <br /> analyzed for TPH (diesel) and PAH' s. No compounds were <br /> detected. <br /> o July 13 , 1988- Dames & Moore submits Feasibility Study/ <br /> Remedial Action Plan to San Joaquin Health District. Based <br /> on site-specific risk assessment, Dames & Moore recommends <br /> excavation and on-site bioremediation of all soils containing <br /> TPH concentrations exceeding 10, 000 ppm. Implementation of <br /> remedial alternative will require removal <br />