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iM. Scott Mansholt - 4 - 18 July 2008 <br /> Chevron OVP <br /> Former Tracy Pump Station <br /> However, gaining access to the appropriate parcel for drilling has not been successful and <br /> SAIC indicated that Regional Water Board staff assistance may be needed to communicate <br /> with the property owner. <br /> SAIC proposed that the site be divided into two separate projects for future No Further Action <br /> Required determination/consideration as follows: a) the former pump station facility, storage <br /> tank locations, and the UPRR easement, and b) the offsite parcel, east of the UPRR <br /> easement, where access issues may delay future characterization work. <br /> I have the following comments: <br /> • I concur that the lateral extent of affected soil and groundwater onsite have been <br /> adequately defined; the vertical extent of affected soil has been defined but, <br /> groundwater has not. Additional characterization is needed to determine the vertical <br /> extent of affected groundwater. <br /> • Affected groundwater has been partially delineated offsite. The extent of affected <br /> groundwater to the east-northeast and southeast (offsite) has not been adequately <br /> delineated and additional characterization is needed. <br /> • Additional borings and groundwater sampling is needed east of SB-3, SB--17, and <br /> SB-18, where TPHg was reported in conjunction with elevated concentrations of TPHd. <br /> One of the step-out borings needs to be southeast of SB-18 where 4,400 pg/L TPHd <br /> was reported in groundwater. These borings and associated sampling should <br /> contribute to evaluating the extent of impacts east-northeast-southeast of the Site. <br /> • A delineation boring(s) and sampling are needed east of SB-16 where 2,200 mg/kg <br /> TPHc was reported at 10.5 feet and a petroleum sheen was noted at the groundwater <br /> interface. <br /> • Appropriate laboratory MDLs should be used for respective analysis when comparing <br /> ND results for delineation needs with applicable ESLs and/or PRGs. <br /> • According to the water quality parameters and TDS results (2,200 to 2,800 mg/L), it is <br /> unlikely that new groundwater wells for domestic use would be installed in the <br /> uppermost shallow aquifer identified at the Site. <br /> • 1 concur with SAIC's proposal that additional borings are needed for collecting <br /> groundwater samples for TPHg analysis. <br /> C DH/R/staft\OVP\Tracy PS/SGIR/MEMO/July2008 <br />