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' West Byron Road Project -2 - 15 April 2004 <br /> Tracy, San Joaquin Co. <br /> residential property is currently being characterized by ChevronTexaco. Similarly, two upgradient (south) <br /> sites, Monterosso and Nicholaw, were issued NFA closures by the SJCEHD in 1996 and 1997, <br /> respectively. <br /> ' During the spring and summer of 2003, the City of Tracy installed two parallel 60"diameter storm water <br /> drain pipe (referred to as the Westside Channel Outfall System [WCOS]) generally beneath West Byron <br /> Road and south of the Union Pacific Railroad and former OVP alignments. Prior to excavation activities, <br /> 159 dewatering wells were installed during installation of the storm drain. Soil and groundwater impact d <br /> by crude oil leaking from the former OVP was identified at several locations. ChevronTexaco was <br /> ' responsible for treatment and disposal of groundwater and soil removed during excavation activities. Th <br /> project was completed in latter July 2003. <br /> According to the previous reports, residual petroleum hydrocarbons, identified in the dewatering wells <br /> ' are present in soil and groundwater throughout the site from approximately 5 feet to 20-Feet below <br /> ground surface. Minor quantities of free phase crude oil were observed in soil at a few locations <br /> generally at less than 12-feet. Depth to first encountered groundwater is approximately 12 to 13-feet and <br /> the gradient is north-northwest. <br /> ' CURRENT INVESTIGATION <br /> In October 2003, SAIC conducted a soil and groundwater investigation, advanced borings to collect soil <br /> and groundwater samples for analysis. According to the February 2004 Soil and Groundwater <br /> Investigation Report, the purpose of the investigation was to: a) address data gaps identified in the <br /> previous characterization studies conducted adjacent to West Byron Road; and b) characterize impacted <br /> soil and groundwater identified during the City of Tracy WCOS storm drain installation project. 's <br /> Soil <br /> ' Thirty-six soil borings up to 36 feet deep were advanced along the south side of West Byron Road. <br /> Concentrations of total petroleum hydrocarbons as crude oil (TPH-c) ranging from ND to a maximum of <br /> 8,300 mg/kg(@ 8 feet in SB-19 were reported in the 100 soil samples analyzed. Benzene was not <br /> reported in any samples submitted for analysis. Concentrations of toluene, ethylbenzene and xylenes at <br /> or slightly above method detection limits were reported in a few of the samples. Low concentrations of <br /> PAFIs at or slightly above method detection limits were repotted in several soil samples from various <br /> depths. <br /> Based on review of the boring logs and analytical results, the majority of impacted soil occurs between 4 <br /> and 20 feet. The vertical extent of impacted soil generally was delineated between 24 to 36 feet where <br /> TPH-c ranging from ND to less than 100 mg/kg was reported in several borings. <br /> Groundwater <br /> During the investigation, groundwater samples were obtained from 15 soil borings for analysis. <br /> Concentrations of TPH-d ranging from 59 pg/L to 8,900µg/L were reported in tune of the 15 samples. <br /> BTEX compounds were not detected at or above the laboratory limits in grab groundwater samples. <br /> 1 <br />