ARCHIVED REPORTS_DRAFT - PHASE I REMEDIAL INVESTIGATION REPORT

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Kennedy/Jenks Consultants The results of this investigation confirm previous findings (i.e., Geocon; 2004, 2005) regarding the presence of TPH in groundwater within OU-5, and further confirm that groundwater to the west of OU-5 is also impacted by TPHg, TPHd and TPHmo. The western extent of the TPH in the first-encountered groundwater in AOI 10 has not been delineated, however the TPH in groundwater may extend under the residential area to the west. The vertical extent of TPH in groundwater has not been investigated. 6.6 Site-Wide In addition to the findings summarized in the preceding sections for each of the OUs, some findings are applicable across the former Railyard. 6.6.1 Soil Although shallow soil in numerous locations contains elevated concentrations of TPH, arsenic and/or lead, with some limited exceptions, the available data suggest that these elevated concentrations do not extend to deeper soils. Some of the exceptions are locations in OU-2 and in AOI 10 in OU-5. Elevated concentrations of TPH and lead frequently were found in the same sample, suggesting that one source event may have been responsible for the presence of both constituents. Particularly in shallow soils, in several locations lead was found at concentrations exceeding residential CHHSL and PRG values. Concentrations of arsenic above background concentrations were frequently found in the same samples as elevated lead or TPH. Where encountered, the elevated concentrations of these compounds frequently decrease with increasing depth in soil. Other than lead and arsenic, metals are not considered to be chemicals of further interest at the former Railyard. During the subsurface investigations performed in December 2005 and January 2006, more than 100 soil samples collected from OU-2, OU-4 and OU-5 were submitted for analysis of VOCs. An additional 50 soil samples from OU-5 were analyzed for BTEX and MTBE. On the basis of the analytical results presented in this Report, with the exception of AOI 10, VOCs are not considered chemicals of further interest at the former Railyard. Based upon analytical results from previous subsurface investigations, BTEX should be included in the analytical suite for any additional investigations performed in the vicinity of Boring B-G4 in AOI 10. On the basis of the subsurface investigations described in this Report, SVOCs, PAHs and pesticides are not considered to be chemicals of further interest at the former Railyard. As described in Section 5.8, arsenic is naturally occurring constituent in soil at the Railyard. The mean arsenic concentration entrations of arsenic samples sen csoil n Calgorgia The 95% l upper toth lerance lerance values of background co limit is 9.24 mg/kg. DRAFT Phase I Remedial Investigation Report Page 45 Former Tracy Railyard, Tracy, California g:Gs-group\admin\iob\05\0565777.18_uprr\Og-reports\ri rpt\text.doc