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Soil and Groundwater Investigation Report and
<br /> Second Quarter 2005 Monitoring and Sampling, US Can-Welty Road October 2005
<br /> Currently, Kinder Morgan Energy Partners, L. P. (KM), operates a pipeline that is located between the
<br /> subject site and Highway 33, and reportedly transports gasoline,jet fuel, and diesel. Western Farm
<br /> Service(WFS) is located directly northeast of the site across Highway 33; WFS has stored and distributed
<br /> bulk liquid and dry fertilizers since 1969. In addition,a former Union Oil gas station, reportedly located
<br /> northeast of the site, operated from approximately 1972 until the mid 1980s. The subject site and soil
<br /> boring locations are presented on Figure 2.
<br /> 2.1 GEOLOGY AND HYDROGEOLOGY
<br /> .. Regionally, the study area is encompassed within the Tracy Sub-basin(Groundwater Basin Number
<br /> 5-22.15)and consists of unconsolidated to semi-consolidated sedimentary deposits that are bounded by
<br /> the Diablo Range on the west, the Mokelumne and San Joaquin rivers on the north, the San Joaquin River
<br /> to the east, and the San Joaquin-Stanislaus County line on the south. The Tracy Sub-basin is located
<br /> adjacent to the eastern San Joaquin Sub-basin on the east and the Delta-Mendota Sub-basin on the south
<br /> (Department of Water Resources [DWR], Revised Draft Bulletin 118). The above-mentioned sub-basins
<br /> are located within the larger San Joaquin Valley Groundwater Basin.
<br /> The Tracy Sub-basin is comprised of continental deposits of Late Tertiary to Quaternary age, which
<br /> include the Tulare Formation, Older Alluvium, Flood Basin Deposits, and Younger Alluvium. The
<br /> thickness of these formations ranges from a few hundred feet in the western foothills to about 3,000 feet
<br /> near the eastern margin of the basin (DWR, Revised Draft Bulletin 118). The Tulare Formation is
<br /> comprised of semi-consolidated, poorly sorted, discontinuous deposits of clay, silt, and gravel. The
<br /> Corcoran clay is situated near the top of the Tulare Formation, separating groundwater in the basin into
<br /> ` what has been reported as two primary aquifers. The upper aquifer is reported to range in thickness from
<br /> 15 to 250 feet below ground surface(bgs)and the lower aquifer is reported at a depth of 600 feet bgs.
<br /> ` Locally,the study area is situated at an approximate elevation of 103 to 105 feet above MSL and has a
<br /> relatively flat topography that slopes gently downward to the northeast. Groundwater in the upper
<br /> water-bearing zone flows in a northeasterly direction and is hydraulically controlled by low-permeable,
<br /> unconsolidated sediments. Generally, depth to groundwater near the site varies from 20 to 40 feet bgs.
<br /> ` Soils encountered appear to be fine-grained unconsolidated sediments, consisting mainly of lean clays and
<br /> silts(CL, ML), clayey and silty sands(SC, SM)with smaller quantities of poorly graded sand and gravel
<br /> (SP, GP).
<br /> 3. PREVIOUS ENVIRONMENTAL ACTIVITIES
<br /> The following information is a brief history of previous environmental investigations conducted at and in
<br /> 6. the vicinity of the site:
<br /> 1995: March 30—ERM, Inc. collected 11 surface soil samples (S-1 through S-1 1) in the vicinity of the
<br /> ` can fabrication plant waste/bum pit area. Oil and grease (O&G) was detected in four of the soil
<br /> samples(S-4, S-5, S-6, and S-8)and concentrations ranged from 1,500 milligrams per kilogram
<br /> (mg/kg)to 5,200 mg/kg. Gasoline was detected in two of the soil samples (S-4 and S-5) and
<br /> .� concentrations ranged from 20 mg/kg to 6,000 mg/kg.
<br /> May 9— ERM, Inc. conducted four hand borings (HB-3, HB-4, HB-5, and HB-6)to 10 feet bgs in
<br /> order to establish the lateral and vertical extent of petroleum-affected soil near the northeastern
<br /> side of the can fabrication plant. Petroleum-affected soil was identified in three borings.
<br /> Benzene, toluene, ethylbenzene, and xylenes(BTEX), and trichloroethene(TCE)were the main
<br /> compounds detected in the soil samples. Concentrations of these constituents varied from 0.4
<br /> ` mg/kg to 16 mg/kg.
<br /> November 29— W HF, Inc. and SEMCO excavated an exploratory trench to 19 feet bgs (near the
<br /> northeastern side of the can fabrication plant)and collected one soil sample at 14 feet bgs. Total
<br /> 2 Rom Science to solutions.
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