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Sod Sampling During Station Demolition, Tosco(Former Unocal) SS#6981, Stockton, CA
<br /> August 29, 2000
<br /> Five sod samples labeled Dl through D5 were collected from native material beneath the former product
<br /> dispenser island locations at approximately 3 5 feet bgs to 5 5 feet bgs Discoloration and hydrocarbon
<br /> odors were encountered at the locations of samples D2 and D4 After discussions with Ed Ralston of
<br /> Tosco, Ms Lagono and Mr Kith, it was decided to return at a later date to over-excavate these areas The
<br /> native sod from the former product dispenser islands consisted of silty clay to clayey slit
<br /> Nine soil samples labeled PLl through PL9 were collected from the former product line locations from
<br /> native materials at approximately 2 5 feet bgs to 4 75 feet bgs The native soil from the former product line
<br /> locations consisted of silty clay to clayey silt
<br /> On April 27, 2000, GR returned and collected six sod samples (TPI through TP6) from native soil at the
<br /> base of the UST pit at approximately 17 feet bgs to 21 feet bgs and labeled Mr Kith of the SJCPHS-EHD
<br /> was present for UST pit soil sampling activities The native soil in the UST pit consisted of silty clay In order
<br /> to collect these samples, a ramp was constructed into the UST pit by excavating soil from the north
<br /> sidewall This sod was stockpiled for characterization and disposal Mr Kith of the SJCPHS-EHD noted
<br /> an area of discoloration in the sidewall of the excavation ramp, near the location of sample PL6 This
<br /> area was noted and marked for later over-excavation
<br /> Over-excavation and Compliance Soil Sampling Activities
<br /> On May 3, 2000, GR returned to over-excavate the areas noted during UST removal activities Ms Margaret
<br /> Lagono of the SJCPHS-EHD was present for these activities Approximately 100 cubic yards (yds) of
<br /> sod were over-excavated from the locations of sod samples D2, D4, and the UST pit ramp area The
<br /> • areas were excavated until all obviously impacted soil (i a discolored and with an odor) were removed
<br /> Soil samples were then collected from the base of each excavation (labeled D2-6', D4-5 5', and
<br /> PL1O'17') Limits of the over-excavations are shown on Figure 3 Analytical results are shown to
<br /> Table 1
<br /> Disposal Characterization Sampling
<br /> On April 27, 2000, GR sampled approximately 650 yd3 of stockpiled pea gravel that had been excavated
<br /> from around and above the former USTs prior to their removal and from the area of the former product
<br /> dispensers and piping Mr Kith of the SJCPHS-EHD was present for stockpile sampling activities Eight
<br /> composite samples, labeled SPI (A-D) through SP8 (A-D), were collected Excavated soil from the UST
<br /> pit ramp, approximately 40 yd3, was stockpiled separately and one composite sample, labeled SP9 (A-D)
<br /> was collected Finally, approximately 60 yd3 of pea gravel from within the UST pit was stockpiled
<br /> separately, and one composite sample, labeled SPIO(A-D), was collected In all,approximately 750 yd3 of
<br /> pea gravel and excavated soil was stockpiled and sampled
<br /> On May 3, 2000, GR sampled approximately 100 yd3 of soil from the over-excavated locations of soil
<br /> samples D2, D4,and the UST pit ramp area One composite sample, labeled SPI l (A-D)was collected
<br /> SAMPLE ANALYSES
<br /> Soil samples from the former UST pit(TP 1 through TP6), the former product dispenser islands(DI through
<br /> D5), the former product piping trenches (PLI through PL9), and the over-excavated locations (D2, D4,
<br /> PLIO) were analyzed for TPHg benzene, toluene, ethylbenzene, and total xylenes (BTEX) and methyl
<br /> . tertiary-butyl ether (MtBE) by DHS LUFT Methodology These samples were also analyzed for fuel
<br /> oxygenates(TBA,MtBE,DIPE,TAME,and ETBE), 1,2-DCA,and EDB by EPA Method 8260A
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