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' '.uNAGEf15 OESK;NEFS fANSWTANTS .Illi _ - i 1.0 INTRODUCTION This report presents the procedures and results of a soil and groundwater investigation conducted by Roy F. Weston, Inc. TO in the former vicinity of a 500-gallon w i (WESTON) y g ante oil underground storage tank,(UST) at Pep Boys Store #711, 4987 West Lane, Stockton, California (Figure 1). The investigation consisted of the completion of four soil �liborings in the former vicinity of the UST and the submittal of ten soil samples and three grab groundwater samples for analysis. In July 1996 WESTON collected a soil sample from underneath the waste oil UST fill line (Drain-1) and a sample from the fill line excavation stock pile (Stock Pile-1). Total petroleum hydrocarbon's as diesel (T?H-D) were detected at 10 mg/Kg in sample Drain-1. No other organic analytes were detected in these two samples. In October 1996 WESTON supervised the removal of the waste oil UST. During the removal ! of the UST WESTON collected a soil sample from the base)of the excavation (WL-Bottom) and from the soit'stock pile (WL-Stock). Organic analytes detected in the sample collected from the bottom of the excavation (7 feet below ground surface) included benzene at 20 ug/kg, toluene at 250 ug/kg ethylbenzene at 66 ug/kg, total xylenes at 4401 ug/kg (M- ethod 8020), and purgable hydrocarbons as gasoline (TPH-G) at 3.3 mg/kg. A summary of the analytical results of soil samples collected during the removal of the fill line and UST is presented in Tables 1 and 2. As a result 'of the detection of organic analytes in the s' it sample collected from the UST excavation pit San Joaquin County Public Health Services (SJCPHS) required that Pep Boys k conduct an investigation to determine if groundwater was impacted and the horizontal and vertical limits of soil contamination. WESTON submitted -Jwork plan and work plan addendum - for the required investigation in May and September 1997:11! ` I I, L:\....\PEPBOYS\W=1_N.PEP 1 Nov.1997