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' ��11!�C�14�Lw'�Wnri C1.._/LkOUP SE 0.VICE5 1.0 INTRODUCTION Clayton Group Services, Inc (Clayton)prepared this document at the request of The Learner Company to summarize site activities and to request closure from the San Joaquin County Environmental Health Department (EHD) The Learner Company facility is a scrap metal recycling operation that receives scrap metal and processes it for shipment and sale to offsite buyers The facility is located at 2711 Navy Drive in the Port 1 of Stockton (the site), as shown on Figure 1 Impacted soil was encountered at the site during underground storage tank (UST) removal activities The facility layout, including the former location of the USTs, is depicted on Figure 2 2.0 BACKGROUND The UST system at the site consisted of a 4,000-gallon tank that stored gasoline and a 10,000-gallon tank that stored diesel fuel This system was used to fuel site vehicles ' The USTs were removed in August 1996 and impacted soil was identified Pursuant to discussions with the EHD, The Learner Company characterized a stockpile of soil that was generated during UST excavation and prepared it for use as backfill The characterization results indicated that the soil was primarily impacted by diesel fuel (up to 5,400 milligrams per kilogram [mg/kg]), with lesser amounts of gasoline (up to 100 mg/kg), ethylbenzene (1 5 mg/kg) and total xylenes (7 1 mg/kg) The soil stockpile was mixed several times between December 1996 and March 1997 to introduce oxygen in an effort to enhance biodegradation of the hydrocarbons Approximately 93 cubic yards of impacted soil was used to backfill the excavation in March 1997 ' The EHD also required The Learner Company to investigate the soil near the former UST system to determine the vertical and lateral extents of the hydrocarbon impact The ' Learner Company contracted Clayton to prepare the document entitled Underground Storage Tank Site Investigation Workplan (Clayton, June 1997) This document prescribed the sampling of soil and groundwater from a minimum of eleven locations within and surrounding the former location of the UST system The EHD approved the site investigation workplan in a letter dated June 12, 1997 The Learner Company contracted Klernfelder to implement the site investigation workplan in October 2000 Klernfelder presented the results of their investigation in the document entitled Limited Soil and Groundwater Sampling Report (Klernfelder, January ' 12, 2001) During the site investigation, soil samples were collected within the excavation backfill horizon that contained the impacted soil (2 to 5 5 feet) at boreholes GP-1, GP-2, and GP-9 The analytical results for these samples indicated diesel range hydrocarbons ranging to 39 mg/kg, and no detectable gasoline range hydrocarbons, ethylbenzene, or xylenes These results indicate that the biodegradation was effective for this material and that limited concentrations of hydrocarbons remain The site investigation also detected moderate to elevated diesel range hydrocarbons in ttwo samples, each collected from within the boundaries of the former excavation The l S 1Proj1P0226MProject Summary and Request for Closure doc