|
In December 1998, three 8,000-gallon gasoline USTs and their associated
<br /> dispensers and piping were removed from the site. Approximately 300
<br /> tons of contaminated soil were excavated in the process and later
<br /> disposed of off-site at the Forward Landfill. During the UST removal
<br /> operations, samples were collected from the excavation, pipe trenches,
<br /> stockpiles, and water within the pit. Soil samples collected within the
<br /> excavation contained up to 33 ppm TPH-G, 0.076 ppm benzene 0.72 p p nl
<br /> toluene, 0.52 ppm ethyl benzene, 3 ppm total xylenes, and 0.71 p p m
<br /> MTBE. Soil samples collected within the piping trenches contained up to
<br /> 160 ppm TPH-G, 0.6 ppm benzene, 1 ppm toluene, 22 ppm ethyl benzene,
<br /> 220 ppm total xylenes, and 2.5 ppm MTBE. Soil samples collected from
<br /> the stockpiles contained up to 470 ppm TPH-G, 0.75 ppm benzene, 21
<br /> ppm toluene, 7.1 ppm ethyl benzene, 44 ppm total xylenes, 10 ppm MTBE,
<br /> and 6.5 ppm tertiary butanol (TBA). The groundwater sample collected
<br /> from the UST excavation contained 66,000 ppb TPH-G, 2,700 p p b
<br /> benzene, 10,000 ppb toluene, 720 ppb ethyl benzene, 12,000 ppb total
<br /> xylenes, and 28,000 ppb MTBE.
<br /> 2..3 1999 UST Installation
<br /> In early 1999, two 10,000 gallon USTs were installed at the site in a
<br /> different location on the property from the previous USTs. New lines and
<br /> dispensers were also installed.
<br /> 4 October 2000 CPT Drilling Site Assessment
<br /> On October 4, 2000, ASE drilled soil borings CPT-1 and CPT-2 at the site
<br /> using a CPT direct push drill rig (Figure 2). Soil beneath the first water
<br /> bearing zone, the bottom of which is no deeper than 16-feet bgs,
<br /> generally consisted of low to very low permeability sediments to a total
<br /> depth of at least 70-Feet bgs. Only a couple of very thin sand or sandy
<br /> silt lenses, no thicker than 1-foot in thickness, were located in the very
<br /> low permeability unit. The soil sample collected at 7.0-fect bgs in boring
<br /> CPT-1 contained 260 ppm TPH-G and 0.66 ppm ethyl benzene. The soil
<br /> sample collected at 7.0-feet bgs in boring CPT-2 contained 6,500 p p m
<br /> TPH-G, 12 ppm benzene, 87 ppm toluene, 91 ppm ethyl benzene, 410 p p m
<br /> total xylenes, and 0.56 ppm MTBE. The only compound detected above
<br /> the laboratory reporting limit in groundwater samples collected from
<br /> boring CPT-1 was total xylenes at 0.56 ppb in the groundwater sample
<br /> .. collected from 41-feet bgs. No groundwater samples could be recovered
<br /> during a sampling attempt from a sandy silt lens at 57-feet bgs. The
<br /> 574 West Grand Line Road, Tracy, CA Workplan — April 2001
<br /> -2-
<br />
|