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Soil Sampling During Station Demolition, Tosco(Former Unocal) SS#6981, Stockton, CA August 29, 2000 Five soil samples labeled D1 through D5 were collected from native material beneath the former product dispenser island locations at approximately 3 5 feet bgs to 5 5 feet bgs Discoloration and hydrocarbon odors were encountered at the locations of samples D2 and D4 After discussions with Ed Ralston of Tosco,Ms Lagorto and Mr Kith, it was decided to return at a later date to over-excavate these areas The native soil from the former product dispenser islands consisted of silty clay to clayey silt Nine soil samples labeled PL1 through PL9 were collected from the former product line locations from native materials at approximately 2 5 feet bgs to 4 75 feet bgs The native soil from the former product line locations consisted of silty clay to clayey silt On April 27, 2000, GR returned and collected six soil samples (TPl through TP6) from native soil at the base of the UST pit at approximately 17 feet bgs to 21 feet bgs and labeled Mr Kith of the SJCPHS-EHD was present for UST pit soil sampling activities The native soil in the UST pit consisted of silty clay In order to collect these samples, a ramp was constructed into the UST pit by excavating soil from the north sidewall This soil was stockpiled for characterization and disposal Mr Kith of the SJCPHS-EHD noted an area of discoloration in the sidewall of the excavation ramp, near the location of sample PL6 This area was noted and marked for later over-excavation Over-excavation and Compliance Soil Sampling Activities On May 3, 2000, GR returned to over-excavate the areas noted during UST removal activities Ms Mararet L.agorio of the SJCPHS-EHD was present for these activities Approximately 100 cubic yards (ydof soil were over-excavated from the locations of soil samples D2, D4, and the UST pit ramp area The areas were excavated until all obviously impacted soil (i a discolored and with an odor) were removed Soil samples were then collected from the base of each excavation (labeled D2-6', D4-5 5', and PL10'17') Limits of the over-excavations are shown on Figure 3 Analytical results are shown in Table 1 Disposal Characterizahon Sampling On April 27 2000 GR sampled approximately 650 yd3 of stockpiled pea gravel that had been excavated from around and above the former USTs prior to their removal and from the area of the former product dispensers and piping Mr Kith of the SJCPHS-EHD was present for stockpile sampling activities Eight composite samples, labeled SPI (A-D) through SPS (A-D), were collected Excavated soil from the UST pit ramp, approximately 40 yd3, was stockpiled separately and one composite sample, labeled SP9 (A-D) was collected Finally, approximately 60 yd3 of pea gravel from within the UST pit was stockpiled separately, and one composite sample, labeled SPIO(A-D),was collected In all,approximately 750 yd3 of pea gravel and excavated soil was stockpiled and sampled On May 3, 2000, GR sampled approximately 100 yd3 of soil from the over-excavated locations of soil samples D2, D4,and the UST pit ramp area One composite sample, labeled SPI I (A-D)was collected SAMPLE ANALYSES Soil samples from the former UST pit(TPI through TP6),the former product dispenser islands(D1 through D5), the former product piping trenches (PLI through PL9), and the over-excavated locations (132, D4, PLIO) were analyzed for TPHg benzene, toluene, ethylbenzene, and total xylenes (BTEX) and methyl tertiary-butyl ether (MtBE) by DHS LUFT Methodology These samples were also analyzed for fuel oxygenates(TBA,MtBE,DIPE,TAME,and ETBE), 1,2-DCA,and EDB by EPA Method 8260A 140124 07 3