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' ARCADIS Ms. Kathryn Dominic <br /> August 24, 2010 <br /> ' RWQCB Request:The RWQCB requested in the February 19, 2009 letter to UPRR <br /> that soil gas samples be collected from the Biotreatment Beds to evaluate possible <br /> ' concentrations of VOCs in the Biotreatment Beds. <br /> ARCADIS Resoonse: ARCADIS did not conduct soil gas sampling for VOCs because <br /> the Biotreatment Beds were designed to treat sludge and soil excavated from the <br /> former surface impoundments that separated oil and water. Only TPH-d and PAHs <br /> were determined to be COCs at the former surface impoundments. VOCs are not <br /> ' associated with the Biotreatment Beds. <br /> Site soils have been extensively sampled for VOCs and investigations point to a <br /> ' source other than the TPCA pond. In addition, VOCs have not been detected above <br /> cleanup goals in wells directly downgradient of the Biotreatment Beds (MW-5A and <br /> MW-7A) and the TPCA ponds (MW-02A and MW-OSA). Appendix A provides of <br /> ' figures and data tables from the Remedial Investigation Report for the Southern <br /> Pacific Transportation Company, Tracy Yard, prepared by Industrial Compliance and <br /> ' dated May 2, 1994. <br /> Polynuclear Aromatic Hydrocarbons <br /> ' Previous investigations in which samples were collected and analyzed for PAHs <br /> include the following: <br /> ' In 1995, 15 soil samples were analyzed for total PAHs during the Phase II <br /> bioremediation confirmation sampling (Terranext 1997). Total PAHs were detected <br /> in nine of the samples analyzed. Eight samples were analyzed for soluble PAHs <br /> ' using the California Waste Extraction Test with deionized water(DI WET). Soluble <br /> PAHs(naphthalene)were detected in one sample at a concentration of 4.0 <br /> ' micrograms per liter(pg/1), which is significantly lower than the cleanup level of 20 <br /> pg/I for total PAHs. <br /> • In 1996, 15 soil samples were analyzed for soluble PAHs using the DI WET as part <br /> ' of the Phase III bioremediation efforts (Terranext 1997). Concentrations of soluble <br /> PAHs were below detection limits in all 15 soil samples. These samples were not <br /> run for total PAHs as approved by the RWQCB. <br /> ' In 1994, 1996 and 1997, 47 A-and B-zone monitoring wells were sampled for <br /> PAHs. PAHs were detected in twelve wells(MW-6A, MW-7A, MW-11A, MW-22A, <br /> ' TW-01, TW-02, TW-04, PZ-01, PZ-02, P-4, and P-5. Total PAH concentrations <br /> ranged from 0.26 pg/L in MW-11 BR(October 1996)to 648.5 pg/L in PZ-02 <br /> Page: <br /> ' 5/12 <br />