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CLOSURE REPORT SWETT AND CRAWFORD BUILDING 711 N. Pershing Avenue Stockton, CA 1.0 INTRODUCTION 1.1 Purpose This report describes the investigation of hydrocarbon contamination on property located at 711 N. Pershing Avenue in Stockton, California. The investigation was authorized by Mrs. Marianne Snell, one of the property owners, and was undertaken at the request of the Swett & Crawford Group, tenants of the building on the site. The Central Valley Region Water Quality Control Board delegated regulatory oversight responsibility to the San Joaquin County Public Health Service, Environmental Health Division. Mr. Michael Infuma of PHSIEHD has supervised the investigation. 1.2 Site Location and Description The site is located in western Stockton, near the Pershing Avenue off-ramp to Interstate 5 (Figure 1). The Stockton Deep Water Channel is located approximately one-half mile to the south of the site. The area was a marsh until about 1945, when it was drained, cleared, and developed by the U. S. Navy. Naval housing units were constructed on the site and were occupied until 1965. They were demolished in 1979. The Swett & Crawford Group redeveloped the site in 1980 and constructed the present office building. The area is zoned primarily for residential use, although commercial buildings are located along Oak Street and other nearby streets to the south of the site. 1.3 Background As part of an intended property purchase in 1993, Swett & Crawford retained RESNA Industries of Sacramento perform a limited soil investigation to determine whether any contamination might be present. Fodr shallow (5-foot) borings were drilled, and a soil sample was collected at the bottom of each boring. Hydrocarbons with the molecular weights of diesel, oil, and grease were detected at fairly low concentrations in three samples, one of which also contained high concentrations of the pesticides chlordane and DDT. This prompted Swett & Crawford to delay the property transaction pending 'r further investigation. ZI 3.71 S Continuing the investigation in November 1994, Upgradipxtt Environmental sampled five more shallow �b borings, mostly on adjacent properties(Figure 2). A sixth boring{ 6)was drilled in December 1994; none found evidence of contamination. In November 1995, three additional borings were drilled in the t$+ q general vicinity of B-4, where RESNA had encountered the high concentration of pesticides, forming an equilateral triangle with 10-foot sides(Figure 3). Chlordane and DDT were detected in one of these (SP-8) at a depth of 6 feet. Concentrations were between 200 and 300 parts per billion, roughly 0.1% of those previously reported by RESNA. 1