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Wendy L. Cohen -5- 1 December 1994 <br /> 21. Page 4-12, Item 4.3.5, Bio-Treatability Study <br /> Report: Phosphate and nitrate were not detected in either of the B-zone samples. This <br /> suggests that available nutrients may be present in the B-zone. <br /> Comment: The two statements are contradictory. <br /> 22. Page 5-3, Item 5.1.5, POS Pipelines and Utilities <br /> Report: Details of the three POS pipeline trench configurations and abandonment are <br /> unknown. <br /> Comment: EMCON or the STTC should ask the POS for more information. <br /> 23. Page 5-4, Item 5.1.6, Migration Pathways Investigation, Water Production Wells <br /> Comment: EMCON should request information from the POS, PHS, and the Department of <br /> Water Resources. I will make a similar request to these agencies. <br /> 24. Page 5-4, Item 5.1.7, Migration Pathways Investigation, Unocal Terminal <br /> Report: The Board, in a letter dated 6 June 1994, recommended that the site be closed. <br /> Comment: The STTC has all of Unocal's reports, but has not provided any comments on <br /> these reports. With regards to additional action at the site, I obtained concurrence with <br /> EMCON and the STTC that the site can be recommended for closure. Furthermore, Unocal <br /> operated an underground storage tank (UST). Contamination attributable to its UST operation <br /> has been remediated as evidenced by soil and ground water data surrounding the former UST. <br /> The Unocal MWs showing contamination are closer to the STTC facilities than to the former <br /> Unocal USTs. <br /> 25. Page 5-6, Conclusions, Historic Tenant and Land Use <br /> Report: The source of TPHd in the vadose zone soils outside the STTC and in areas where <br /> the A-zone ground water did not contain detectable petroleum hydrocarbons is unknown. <br /> Comment: My review of the IPAR shows that the TPHd soil contamination ranges from <br /> 5 1Ag/1 to 240 µg/1 to the east of ST Services, Unocal, and Union Pacific except in the section <br /> east of sample location PS/CB-16. The low TPHd concentrations in the soil have not resulted <br /> in ground water contamination. TPHd in the soil might not need to be remediated. <br /> 26. Page 5-6, Conclusions, Historic Tenant and Land Use <br /> Report: Oil and grease stains on surface soils at Learner Lease indicate other potential <br /> sources of soil and ground water may exist south of the STTC facilities. <br /> Comment: As stated previously, Learner Lease is south and downgradient of the STTC <br /> facilities and thus is an unlikely source of the contamination to the STTC plume. <br />