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<br /> QUARTERLY GROUNRWATER MpNfTi]ftlNG REPORT
<br /> 3725 Tracy Boulevard Tracy Calkfornla
<br /> 1.0 INTRODUCTION
<br /> This report documents the results of quarterly groundwater monitoring conducted by
<br /> Emcon Associates (Emcon) of Sacramento, California, on February 14, 1992, at the Shell
<br /> I oil Company (Shell) service station located at 3725 Tracy Boulevard in Tracy, California
<br /> (Figure 1) The monitoring included collection of depth-to-groundwater measurements
<br /> and water samples from three wells (MW-1A, MW-2A, and MW-3A) located on site
<br /> (Figure 2) This report is based, in part, on information obtained by Aegis from Shell and
<br /> Emcon, and is subject to modification as newly acquired information may warrant
<br />' 2.0 SITE DESCRIPTION
<br />' The Tracy Boulevard Shell site is an active service station that retails unleaded-regular,
<br /> super-unleaded regular, and super-unleaded gasolines Details of the site's former
<br /> facilities, including underground storage tanks (UST), were reported to Shell by Delta
<br />' Environmental Consultants, Inc. (Delta), of Ranch Cordova, California, in a "Preliminary
<br /> Report and Tank Closure Report," dated November 28, 1990 The project site is located
<br /> in a commercial area of Tracy, California
<br /> 3.0 BACKGROUND
<br /> The site was developed as a service station in 1967 Initially, two UST were installed, one
<br /> 8,000-gallon and one 10,000-gallon capacity A third 8,000-gallon tank was installed in
<br />' 1970 In 1985, the three UST and a waste-oil tank were removed Soil and groundwater
<br /> samples were collected from the tank basin The soil samples'contained concentrations
<br />' of total petroleum hydrocarbons (TPH), as gasoline, ranging from below method detection
<br /> limits (BDL) to 40 parts-per-million (ppm) and from BDL to 0 0012 ppm toluene (Delta
<br /> report to Shell dated November 28, 1990) The soil samples were BDL for benzene,
<br />' toluene, ethylbenzene, EDB, and organic-lead compounds A groundwater sample
<br /> collected from the tank excavation contained concentrations of TPH, as gasoline, of
<br /> 0 5 ppm, and benzene of 0 026 ppm The location and installation date of the waste-oil
<br /> ' tank are unknown
<br /> In September 1989, three groundwater monitoring wells, MW-1, MW-2, and MW-3, were
<br /> ' installed by Delta Soil samples were collected from the borings and submitted to a
<br /> state-certified analytical laboratory All samples collected were BDL for TPH, as gasoline,
<br /> and benzene, toluene, ethylbenzene, and total xylenes (BTEX) (Delta report to Shell dated
<br /> ' November 28, 1990) In May 1990, a concrete vault was discovered during station
<br /> reconstruction The vault was removed in June 1990 Analytical laboratory results from
<br /> soil samples collected from the vault excavation were BDL for TPH, as gasoline, and
<br /> BTEX (Delta report to Shell dated August 23, 1990)
<br /> 1 90-089A QMR
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