SITE INFORMATION AND CORRESPONDENCE

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i West Byron Road Project _ 2 _ Tracy, San Joaquin Co. 15 April 2004 residential property is currently being characterized by ChevronTexaco. Similarly, two upgradient(south) sites, Monterosso and Nicholaw, were issued NFA closures by the SJCEHD in 1996 and 1997, respectively. During the spring and summer of 2003, the City of Tracy installed two parallel 60"diameter storm water drain pipe(referred to as the Westside Channel Outfall System [WCOS])generally beneath West Byron Road and south of the Union Pacific Railroad and formes-OVP alignments. Prior to excavation activities, 159 dewatering wells were installed during installation of the storm drain. Soil and groundwater impacted by crude oil leaking from the former OVP was identified at several locations. ChevronTexaco was ' responsible for treatment and disposal of groundwater and soil removed during excavation activities. The project was completed in latter July 2003. According to the previous reports,residual etroleum h dro P y carbons, identified in the dewatering wells are present in soil and groundwater throughout the site from approximately 5 feet to 20-feet below _ ground surface. Minor quantities of free phase crude oil were observed in soil at a few locations generally at less than 12-feet. Depth to first encountered groundwater is approximately 12 to I3-feet and the gradient is north-northwest. CURRENT INVESTIGATION In October 2003,SAIC conducted a soil and groundwater investigation, advanced borings to collect soil 1 and groundwater samples for analysis. According to the February 2004 Soil and Groundwater Investigation Report, the purpose of the investigation was to: a) address data gaps identified in the _ previous characterization studies conducted adjacent to West Byron Road; and b) characterize impacted soil and groundwater identified during the City of Tracy WCOS storm drain installation project. ' Soil o ' Thirty-six soil borings u to 36 feet ' g p deep were advanced along the south side of'West Byron Road. Concentrations of total petroleum hydrocarbons as crude oil (TPH-c) ranging from ND to a maximum of 8,300 mg/kg(@ 8 feet in SB-19 were reported in the 100 soil samples analyzed. Benzene was not ' reported in any samples submitted for analysis. Concentrations of toluene, ethyl benzene and xylenes at or slightly above method detection limits were reported in a few of the samples. Low concentrations of PAKs at or slightly above method detection limits were reported in several soil samples fi-om various i depths. Based on review of the boring logs and analytical results, the majority of impacted soil occurs between 4 ' and 20 feet. The vertical extent of impacted soil generally was delineated between 24 to 36 feet where TPH-c ranging from ND to less than 100 mg/kg was reported in several borings. � Groundwater During the investigation, groundwater samples were obtained from 15 soil borings for analysis_ Concentrations of TPH-d ranging from 59µg/L to 8,900 lrg/L were reported in rune of the 15 samples. BTEX compounds were not detected at or above the laboratory limits in grab groundwater samples.