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• Mr. Jeff Baker - 3 - 16 November 2009 <br /> Stockton Terminals Technical Committee <br /> TS-4R, TS/M-2, and TS-5 for chromium, hexavalent chromium (Cr VI), vanadium, <br /> bromide, and bromate. Potential injection wells TS/RW-1 and TS-4R are being <br /> monitored for the presence of SPH, which was not observed during the third quarter. <br /> The baseline monitoring results show that low concentrations of all target compounds, <br /> except bromate, have periodically been detected in the baseline monitoring wells. <br /> BP's 29 October 2009 Helium Tracer Study for Biosparging Feasibility Report (Report) <br /> summarizes the results of a two-day A zone biosparge feasibility study on the BP <br /> facility to evaluate communication between potential injection and monitoring wells. The <br /> Tracer Study was conducted on 25 and 26 August 2009 by applying a 90 percent (%) <br /> oxygen-10 % helium mixture into injection well IS-2 and observing monitoring wells <br /> AR/MW-5A and AR/MW-50 for a response. No evidence of communication was <br /> observed during the first day. On the second day, BP switched to sparging the oxygen <br /> instead of applying it at the wellhead, and increased the injection pressure about 10- <br /> fold. Communication was evidenced by the appearance of helium gas in monitoring <br /> well AR/MW-5A. In addition, distinct concentration increases of vapor phase volatile <br /> organics, carbon dioxide, and residual organic carbon (ROC) were also observed in this <br /> well. However, BP concluded that the operating pressures of approximately 40 to 50 <br /> pounds per square inch (psi) greatly exceeded normal biosparge system operating <br /> pressures and presented a potential structural hazard to the nearby AGTs. Therefore, <br /> BP has opted to evaluate alternate remedial technologies including the possible use of <br /> passive diffusers. <br /> Our comments are: <br /> 1 . It appears that the combination of air sparging and increasing injection pressures <br /> resulted in successful communication between BP's IS-2 injection well and the <br /> AR/MW-5A observation well. BP has decided that operating a system at high <br /> pressures presents an unacceptable level of risk in the AGT containment area. <br /> However, the successful communication caused by sparging the oxygen warrants <br /> evaluating whether sparging at lower pressures could also be effective over a longer <br /> time.An active method of introducing oxygen into the water column should be more <br /> effective than the passive method that BP is contemplating. <br /> 2. On 14 September 2009 Mr. Mark Chandler returned the signed documents required <br /> to enroll the TOC facility into our cost recovery program. TOC's cost recovery <br /> account will now enable the STTC consortium to separate out costs for investigation <br /> activities that are limited to the TOC facility. <br /> If you have any questions regarding this letter, you may contact me at (916) 464-4811 <br /> or by email at betaylor@waterboards.ca.gov. <br /> 4R_I <br /> AN P.G. <br /> Engineering Geologist <br /> cc list on next page <br />