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r 16- December 22, 1998 Harding Lawson Associates 4034405 Margaret Lagorio, Supervising REHS San Joaquin County Public Health Services Environmental Health Division ' Page 2 The Site is lust south of industrial facilities in the Port of Stockton and surrounding land use is mainly industrial with minor residential areas Interstate 5 is located lust east of the Site Hydrogoologic Framework The nearest major surface water body is the San Joaquin River at the Stockton Deepwater Channel and Turning Basin, located approximately 0 75 miles north of the Site According to regional groundwater maps compiled in spring of 1996 by the San Joaquin County Flood Control and Water Conservation District (SJCFC/WCD) the depth to groundwater beneath the Site is 15 to 20 feet below ground surface 1 (bgs) (SJCFC/WCD, 1996) The groundwater beneath the Site vicinity flows toward the east (SJCFC/WCD, 1996) Four onsite monitoring wells, associated with the former# 6 fuel oil UST, are located approximately 500 feet southeast of the courtyard in the southeast corner of the Site Groundwater level measurements during the last two years indicate that groundwater depths have ranged from 6 to 20 feet bgs and the flow directions have varied from the northeast through the southeast BACKGROUND In October 1990,American Environmental Management Corporation (AEMC) submitted a report (AEMC, 1990) titled "Unauthorized Release Report for Newark Paperboard Corporation, Stockton, California " The report summarized results of July 1990 soil sampling and recommended closure procedures for the No 6 fuel delivery pipeline and the courtyard tanks (concrete vaults) and sump (concrete) Three angled soil borings were drilled in the vicinity of the courtyard tanks and sump designated NSA-1, NSA-2 and NSA-3 The locations of these borings are shown on Plate 3 Two soil samples were collected from each borehole The borings were drilled to an approximate depth of 20 feet (borehole depth) below giound surface (bgs) Samples collected from approximate 10 and 20 feet within the borings were submitted from each boring for chemical analyses Samples were analyzed for total petroleum hydrocarbons, quantified against a diesel standard (TPHd), total recoverable petroleum hydrocarbons (TRPH), and benzene, toluene, ethylbenzene and total xylenes (BTEX) No BTEX was reported TPHd was only detected in the shallow samples from NSA-1 and NSA 2, with a maximum concentration of 730 milligrams per kilogram (mg/kg) found in NSA-2 TRPH was detected in each sample, with concentrations ranging between 110 and 13,000 mg/kg, with the exception of the deeper sample (20 5 feet bgs) from NSA-3 In October/November 1993, the courtyard tanks and sump were closed in-place by Resna Industries Inc (RESNA)by removing the remaining contents, cleaning, and backfilling with a cement slurry (RESNA, ' 1994) Prior to backfilling, soil samples were collected through the bottom of the tanks and sump through holes placed in the concrete bottoms A total of six soil samples were collected and submitted for TPHd and BTEX TPHd was found to be present in low to moderate concentrations in all but one of the samples collected from beneath the tanks and sump The highest recorded concentration of TPHd (600 mglkg) was detected at the eastern end of the sump This sample was also analyzed for soluble TPH as gasoline TPHg, TPHd, and BTEX Leachable TPHd was reported in the extract at 1 3 milligrams per liter (mg/L) It is not known if the laboratory used deionized water or an acid for this analyses No groundwater was encountered diiiing these activities