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SOIL INVESTIGATION WORK PLAN Heritage Square 640 North San Joaquin Street Stockton, Stanislaus County 1.0 INTRODUCTION This Work Plan for the collection of soil samples beneath two existing underground storage tanks(USTs) located at 640 North San Joaquin Street, Stockton, California has been prepared at the request of the property owner, MT. David Warwick, and the Stockton Unified School District (Stockton Unified), the prospective property buyer. The site is located at the southeast corner of the intersection of North San Joaquin Street and Park Avenue in Stockton, as shown on Figure 1. The purpose of work is to evaluate the potential of subsurface hydrocarbon contamination from previously unidentified-USTs and related ` piping, and the work is part of a Phase 11 Environmental Site Assessment (ESA). Condor Earth ]� Technologies, Inc. (Condor) prepared this Work Plan at the request of Mr. David Warwick and Stockton Unified. All work conducted by Condor will be under the supervision of a California registered geologist or engineer. This Work Plan includes project background information; a description of the field, laboratory, and reporting procedures proposed to conduct the work; and a project schedule. 2.0 PROJECT BACKGROUND The site is located in a commercial area in downtown Stockton currently known as Heritage Square. The existing structure at the site is an unreinforced concrete and masonry building constructed in 1916 that 4 Stockton Unified is proposing to purchase for use as a charter school. Based on the age of the structure and proposed use, Stockton Unified requested that Condor perform a geotechnical investigation at the site to evaluate subsurface foundation conditions. In February 2002, during the geotechnical investigation, a borehole was advanced on the east side of the building, piercing a metal pipe not identified by the Underground Service Alert (USA). A viscous black fluid seeped from the pipe onto the p soil, and one sample of the fluid and underlying soil was collected for laboratory analyses. This sample Lwas analyzed for gasoline, kerosene, diesel and motor oil by Method 8015M; for volatile organic compounds (VOC) by Method 8260.B; and for California Administrative Manual (CAM) metals by EPA Methods 7471A/ 6010B. The location of the borehole B-1 is shown on Figure 2. The hydrocarbons detected in the extractable range are primarily diesel and motor oil. Gasoline was also detected; however, the chromatogram did not match a typical gasoline pattern. The detection of gasoline may result from the weathering of kerosene and motor oil. No CAM metals were detected at or above the Preliminary Remediation Goals (P.RG) for residential sites or Total Threshold Limit Concentrations (TTLC). The laboratory results of hydrocarbon constituents are summarized in Table I on the next page. C�e.aeC C 4 CONDOR