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1 <br /> Chevron Products Company 2 <br /> Chevron Station#9-2033.508 West Charter Way,Stockton.California „ March 19;2001 <br /> f" <br /> SITE BACKGROUND AND PREVIOUS INVESTIGATIONS <br /> The site is an operating Chevron Service Station located in a primarily commercial area <br /> at the intersection of West Charter Way and South Lincoln Street in Stockton, i <br /> California The site currently contains three gasoline underground storage tanks (USTs) <br /> that share a common excavation near the northwest site boundary, four dispenser <br /> islands under a common canopy, and a station building <br /> A Texaco Service Station operates directly east of the site (across Lincoln Street), and <br /> an operating ARCO Service Station is northeast of the site across the intersection The <br /> City of Stockton maintenance yard to the south is reported to have, or have had, one or <br /> more underground storage tanks (USTs) <br /> Chemicals of concern in soil and groundwater at the site include total petroleum <br /> hydrocarbons calculated as gasoline (TPHg), aromatic hydrocarbons including benzene, <br /> toluene, ethylbenzene, and xylene (BTEX), and oxygenates, including methyl tertiary <br /> butyl ether(MtBE), tertiary butanol, di-isopropyl ether (DIPE), ethyl tertiary-butyl ether <br /> (EtBE), tertiary-amyl methyl ether (TAME), 1,2-dichloroethane, (1,2-DCA), 1,2- <br /> chbromoethane (EDB), ethanol, and methanol <br /> The site background relevant to this assessment is included in Attachment B Fourth <br /> quarter 2000 groundwater monitoring results are included in Attachment C <br /> Data collected during the previous Phase II investigation suggests a complex sequence <br /> of interbedded fine grained and sandy layers comprise the top 95 feet of the soils and <br /> unconsolidated sediments beneath the site Groundwater appears to be present in two to <br /> three zones underlying the site The upper water-bearing zone suggests the groundwater <br /> flows to the east—northeast under a hydraulic gradient of 0 005 ft/ft Groundwater in the <br /> uppermost water bearing zone appears confined or semi-confined by overlying fined- <br /> grained mixtures Field observations suggest groundwater rose up to 25-feet above the <br /> level encountered in borings <br /> Figure 2—Site Plan depicts the locations of pertinent site features and proposed CPT <br /> and monitoring well locations Groundwater is found between 35 and 40-feet below <br /> surface <br /> PROPOSED SCOPE OF WORK <br /> This investigation is intended to more completely assess on-site stratigraphy and <br /> determine the water quality in the three previously identified water-bearing zones This <br /> information will be used to determine whether monitoring wells MW-1 and MW-2 are <br /> screened through two water-bearing zones (and therefore should be destroyed), and <br /> used in design aide in the construction of up to four pairs of monitoring wells (four <br /> shallow and four intermediate) A hydraulic evaluation will also be performed to <br /> determine vertical and horizontal gradients beneath the site <br />�1 <br /> 1 1Chevron1920331REP0RTSlfurthcr site assessment WP RevA doe <br />