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' LEVINE•FRICKE EBECUTIVE SUMMARY ' On February 25, 1988, subsurface fuel hydrocarbons were reported in the vicinity of the Southern Pacific Pipelines, Inc. (SPPL) terminal in Stockton, California. The three SPPL pipelines in ' the area of the detected fuel hydrocarbons were immediately shut- down, and an investigation was undertaken by SPPL to determine if the source of the fuel hydrocarbons in the subsurface were the ' result of a pipeline leak. This investigation included excavating exploratory trenches and test pits, fuel hydrocarbon character- ization through chemical analyses, installation of 5 large diame- ter wells, monitoring existing piezometers and pipeline testing. 1 Exploratory trenches and test pits performed by SPPL detected floating hydrocarbons along the pipeline right-of-way for a dis- tance of about 360 feet. No leaks were observed along any sec- tions of the pipelines exposed in the trenches. ' Large diameter (12-inch inner diameter) wells were installed in 5 of the exploratory trenches to monitor floating hydrocarbon thickness at each location, to provide for sample collection points and to extract floating product, if necessary. The thick- ness of the floating hydrocarbons on the ground-water table meas- ured through the wells by SPPL varied from a possible sheen (SP-1, SP-2 and SP-3) to 0.42 feet near the center of the ' affected area (SP-3) . Each of the three pipelines were tested by static monitoring, ' acoustically and by using a tracer gas injection directly into the pipeline. No lea ks were detected in any of the SPPL pipe- lines by any of these testing methods. Fuel characterization show that the hydrocarbons present in the subsurface are 90 to 95% (or greater) fresh re ular leaded aso- line with less than 5 to 10% fuel oil, pro ably diesel fuel. ' Since SPPL transports different types of fuels in their pipe- lines, a preponderance of a single fuel type in the subsurface would not be expected if the source were a continuous pipeline leak. A continuous leak in any of the SPPL pipelines would yield ' a fuel sample that was a mix of the various fuels carried in that particular line. 1 The high concentrations of organic lead and volatile compounds in the analyses also indicate that the subsurface hydrocarbons are the result of a fresh source of leaded gasoline. The hydrocar- bons are probably less than 3 monthG mold. V MAP . V18 ' kN atFGW,/�k�WK.�S Tri