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Chevron Products Company Page 2 Chevron station #9-8632. 575 Grant Line Road Tracy, California March 19 2001 1 ,720 ppb (MW-3) . Benzene was detected in three of four samples at concentrations ranging from 43 .3 ppb (MW-3) to 226 ppb (MW-4). Methyl-tertiary-butyl-ether (MtBE) was detected in all four samples at concentrations ranging from 20.0 ppb (MW-4) to 262 ppb (MW-3) . Groundwater flow has been reported consistently to the northwest at gradients ranging from 0.005 to 0.02 ft/ft. Additional site investigation information pertinent to this proposed assessment is summarized in Attachment A. PROPOSED SCOPE OF WORK The scope of work proposed for this assessment includes the advancement of 15 CPT borings to collect soil stratigraphy and the collection of soil and groundwater samples. Groundwater is anticipated to be encountered at approximately 6 to 7 feet bgs based on recent data. The specific scope of work is discussed below: CPT Borings. Fifteen CPT borings will be advanced in the general locations shown in Figure 2. These borings will be advanced to approximately 30 feet bgs to assess soil stratigraphy in the upper water-bearing zone along the site property boundaries and at one offsite location (east of the site in the sidewalk along Grant Line Road) . Soil and Groundwater Sampling. Immediately adjacent to each CPT borehole, a second direct-push borehole will be advanced to specifically collect discrete soil and groundwater samples. Depths of the discrete soil and groundwater samples will be determined from the CPT logs in the field. One soil sample will be collected from a minimum of 8 of the 15 borings (including the offsite boring) above the first encountered-round__water-(approximatelx5_feet_bgs) One groundwatersample_will_be collected from each of the 15 borings in the first encountered water-bearing zone. Three borings along the northern edge of the property (Figure 2) will be extended to collect a second groundwater sample at approximately 30 feet bgs to assess the need for further vertical delineation of groundwater impacts at the site. Soil and groundwater samples will be analyzed for TPHd by EPA Method 8015, TPHg, benzene, toluene, ethylbenzene, xylenes (BTEX), and the fuel oxygenates MtBE, di- isopropyl ether (DIPE), tertiary amyl methyl ether (TAME), ethyl tertiary butyl ether (EtBE), tertiary butyl alcohol (TBA), ethyl dibromide (EDB), 1,2 dichloroethane ( 1 ,2- DCA), ethanol, and methanol by EPA Method 8260B . Proposed field and laboratory procedures are presented as Attachment B . 11Chevron\98632\Reports\CPT WP_Rev A.doc