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Mr.M. Scott Mansholt—CEMC
<br /> Fourth Quarter 2006 Groundwater Monitoring and Sampling Report and
<br /> Annual Summary Report January 12,2007
<br /> US Can-Welty Road Page 2 of 8
<br /> Currently,Kinder Morgan Energy Partners,L. P., operates a pipeline that reportedly transports
<br /> gasoline,jet fuel, and diesel; it is located between the site and Highway 33. Western Farm
<br /> Service(WFS)is located directly northeast of the site across Highway 33 and has stored and
<br /> distributed bulk liquid and dry fertilizers since 1969. In addition, a former gas station is located
<br /> northeast of the site.
<br /> REGIONAL/LOCAL HYDROGEOLOGY
<br /> Regionally,the site is encompassed within the Tracy sub-basin(Groundwater Basin Number
<br /> 5-22.15)and is defined by unconsolidated to semi-consolidated sedimentary deposits that are
<br /> bounded by the Diablo Range on the west,the Mokelumne and San Joaquin rivers on the north,
<br /> the San Joaquin River on the east, and the San Joaquin-Stanislaus County line on the south. The
<br /> Tracy sub-basin is located adjacent to the eastern San Joaquin sub-basin on the east and the Delta-
<br /> Mendota sub-basin on the south.' These sub-basins are located within the larger San Joaquin
<br /> Valley Groundwater Basin.
<br /> The Tracy sub-basin is comprised of continental deposits of Late Tertiary to Quaternary age,
<br /> including the Tulare Formation, Older Alluvium,Flood Basin Deposits, and Younger Alluvium.
<br /> The thickness of these formations ranges from a few hundred feet in the western foothills to about
<br /> 3,000 feet near the eastern margin of the basin. The Tulare Formation is comprised of semi-
<br /> consolidated,poorly sorted,discontinuous deposits of clay, silt, and gravel. The Corcoran clay is
<br /> situated near the top of the Tulare Formation, separating groundwater in the basin in what has
<br /> 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 600 feet bgs.'
<br /> Locally,the site is situated at an approximate elevation of 103 to 105 feet above mean sea level
<br /> (MSL), and has a relatively flat topography that slopes gently downward to the northeast.
<br /> Groundwater in the upper water-bearing zone flows in a northeasterly direction at an approximate
<br /> gradient of 0.001 feet per foot(ft/ft)and is hydraulically controlled by low-permeable,
<br /> unconsolidated sediments. Based on ongoing groundwater monitoring at the site, depth to
<br /> groundwater varies from 20 to 40 feet bgs. Soils encountered appear to be fine-grained
<br /> unconsolidated sediments, consisting mainly of lean clays and silts (CL,ML) and clayey and silty
<br /> sands, (SC, SM)with smaller quantities of poorly graded sand and gravel(SP, GP).
<br /> PREVIOUS ENVIRONMENTAL ACTIVITIES
<br /> 1995 Site Investigations.2'3 ERM-West,Inc. (ERM) collected 11 surface soil samples(S-1
<br /> through S-11)in the vicinity of the can fabrication plant wasteibum pit area. Oil and grease
<br /> (O&G)were detected in four of the soil samples (S-4, S-5, S-6,and S-8)in concentrations
<br /> ranging from 1,500 milligrams per kilogram(mg/kg)to 5,200 mg/kg. Gasoline was detected in
<br /> two of the soil samples(S-4 and S-5) in concentrations ranging from 20 mg/kg to 6,000 mg/kg.
<br /> ERM advanced four hand borings (HB-3,HB-4,HB-5, and HB-6)to 10 feet bgs to establish the
<br /> lateral and vertical extent of petroleum-affected soil near the northeastern side of the can
<br /> fabrication plant. Petroleum-affected soil was identified in three borings. Benzene,toluene,
<br /> ethylbenzene, and total xylenes(BTEX); and trichloroethene(TCE)were the main compounds
<br /> detected in the soil samples. Concentrations of these constituents varied from 0.4 mg/kg to
<br /> 16 mg/kg.
<br /> 1. California Department of Water Resources,2003. California's Groundwater,Bulletin 118,2003 Update.
<br /> 2. ERM-West,Inc., 1995. Letter to ERM,Inc.,Hunter Container Corporation Soil Sampling.
<br /> 3. ERM-West,Inc., 1995- Letter to US Can Company regarding lab analysis data.
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