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LEVINE•FRICKE INVESTIGATION OF SUBSURFACE FUEL HYDROCARBONS SOUTHERN PACIFIC PIPELINES, INC. STOCKTON, CALIFORNIA ' March 23 , 1988 INTRODUCTION ' On February 25, 1988, stained soils were observed by Time Oil Co. personnel in the vicinity of three buried Southern Pacific Pipe- lines (SPPL) pipelines southwest of the garage on the Tesoro Refining, Marketing and Supply Company (Tesoro) property (Figure 1) . SPPL immediately shutdown the pipelines and began investi- gating the integrity of the pipelines in the immediate area around the stained soils. On February 25 and 26, 1988, SPPL excavated exploratory trenches ' around the pipelines in an effort to determine whether the source of fuel hydrocarbons in the soil originated from an SPPL pipe- line(s) . Subsequently, hydrocarbon samples were submitted for fuel characterization and extensive pipeline testing was per- formed. These activities are described below. FIELD ACTIVITIES Exploratory Excavations And Field Monitoring ' The possible presence of a pipeline leak was initially investi- gated through excavating trenches and small test pits. The loca- tion of the seven largest trenches are depicted on Figure 1. Excavating was performed on February 25 and 26, 1988 with back- hoes under the direct supervision of SPPL personnel. In addi- tion, two shallow piezometers (P-26 and P-27) located on the south side of Charter Way were inspected to assess the presence ' of floating product. Piezometer P-27 is located approximately 200 feet northwest of P-26 . Neither piezometer contained visible floating fuel hydrocarbons. ' The trenches were typically 3 to 4 feet wide and extended verti- cally to expose the pipelines (3-1/2 to 4 feet below grade, depending on grade level) . In a number of locations, trenches were deepened to well below the water table so that the floating product/ground-water interface would be intercepted, if present (4-1/2 to 5 feet below grade) . Test pits were also utilized to ' assess the lateral extent of floating product. The test pits northwest of SP-1 and southeast of SP-5 did not contain floating hydrocarbons. No leak was detected along any of the exposed sections of pipe- -1-