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Mr. Jeffrey Baker • -2 - • 9 May 2003 t <br /> 2. STTC also sampled for hexavalent chromium in the feasibility testing, but does not <br /> discuss the results or why detection limits vaned. STTC must include this information <br /> along with the effect of oxidation on naturally occurring metals. <br /> 3. The CAP includes a mass flux calculation but does not discuss which upgradient wells <br /> were selected for the calculation and does not address whether methyl tertiary butyl ether <br /> (MTBE) is completely destroyed or if some is converted to tertiary butyl alcohol. STTC <br /> must include this information. <br /> 4. The CAP does not address the issue of whether the sparging of ozone has the potential to <br /> release contaminants from the liquid to vapor phase. STTC must include a discussion of <br /> how ozone sparging will destroy the constituents of concern without pushing the plume <br /> further downgradient and not releasing pollutants into the vapor zone. <br /> 5. The CAP proposes natural attenuation for the three lower water bearing zones based on <br /> the rationale that aerobic and anaerobic biodegradation is occurring, the downgradient <br /> plumes are defined, evidence of natural attenuation of MTBE, and slight vertical <br /> gradients. Regional Board staff does not believe natural attenuation is an appropriate <br /> remedial alternative because the plumes in the three lower water bearing zones have <br /> increased in concentration in the downgradient direction since investigative activities <br /> began at the site, and they have migrated off-site,which shows natural attenuation is not <br /> occurring sufficiently to clean up these plumes. In addition, there are not enough data <br /> from the newly installed wells to determine whether the plumes are stable. STTC needs <br /> to evaluate the feasibility of active remedial alternatives for the deep water bearing zones. <br /> 6. The proposed remedial alternative for the A water bearing zone does not address the area <br /> of ST Services, which is part of STTC. This area needs to be included in the CAP. <br /> 7. Section 8.4.3 of the CAP is unclear. STTC describes installation of 48 soil borings for <br /> conversion to ozone injection wells,but 59 ozone sparge wells are proposed. STTC <br /> needs to clarify this discrepancy. <br /> 8. Appendix B of the CAP is a 21 April 2003 Remedial Action Plan (RAP) for the BP/Arco <br /> Terminal. The RAP does not include a signature from the registered professional. <br /> BP/Arco must submit the RAP separately for Regional Board staff review. Upon <br /> preliminary review, Regional Board staff has concerns about the proposal to inject <br /> sulfate and nitrate as a remedial action based on calculations with no pilot or bench-scale <br /> testing proposed. Furthermore, there is no discussion of whether complete degradation of <br /> MTBE will occur with the addition of sulfate/nitrate and whether the wells installed to <br /> test In-Situ Stable Oxygen Generation are appropriate for the injection of sulfate/nitrate. <br /> BP/Arco also needs to-address the pollution in the lower water bearing zones. <br /> 9. The QMR states monitoring well PS/MW-1M was not sampled because the well was not <br /> located. STTC had time before the end of the quarter to locate the well, but there is no <br />