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mr. pert tsakerMMMMI Stockton Terminals Technic Ommittee 4 20 August 2009 • BP's 17 June 2009 Work Plan for Feasibility Study, BP Stockton Terminal No. 40T (Work Plan) proposed to conduct a one- to three-day A zone biosparge feasibility study close to BP monitoring wells MW-5A and MW-50 to evaluate communication between potential injection and monitoring wells. This plan was proposed after BP informed Central Valley Water Board staff that efforts to conduct a nutrient injection study would be discontinued and an alternative proposal for the 12-week study would be submitted. The Central Valley Water Board staff concurred with the work plan in our 13 July letter and requested submission of the report by 30 October 2009. Our comments are presented below. 1. By proposing over-purging in the nine additional monitoring wells to address the MBAS pollution in groundwater at this facility, BP appears to have chosen to implement an interim remedy of groundwater extraction based on the results observed in AR/MW-5A. The laboratory analytical data also indicate that over- purging has reduced the concentrations of other COCs including TPHg, BTEX, and MTBE in AR/MW-5A, so the interim remedy appears promising. By 30 September 2009, we request that BP submit a work plan for this proposed interim remedy that describes the objective and specific procedures of the over- purging, including the quantities of groundwater that will be extracted from each well, a list of all wells to which the interim remedy will be applied, and the metrics by which successful completion of the interim remedy can be evaluated. 2. As requested by Central Valley Water Board staff, BP provided documentation, in Appendix L of the Second QMR, disclosing that a 1,500-gallon release of fire suppression foam occurred on 30 November 2005. However, monitoring for MBAS was not conducted until after the 1 November and 15 November 2008 discharges occurred. In Comment No. 3 of our 17 March 2009 letter, we requested that BP conduct quarterly monitoring in all AR/MW wells for four quarters to assist in determining whether the route of entry of TBA and other constituents of the fire suppression foam was through the monitoring well surface seals. During the second quarter, BP chose to limit MBAS sampling in 29 of the 35 AR/MW wells. MBAS sampling was not conducted in source area well AR/MW-2A, or in cross gradient wells AR/MW-18 B and C and AR/MW-21 A, B, and C. We maintain that determining the lateral extent of the MBAS plume by monitoring all AR/MW wells is critical to determine whether the MBAS plume is now widespread after infiltrating through the ground surface from multiple discharges or whether it entered the groundwater through the well seals following the 15 November discharge. Our requirement for BP to evaluate and provide a determination on this issue is still in place due to the potential for the monitoring wells to serve as conduits for other contaminants to the aquifers underlying the Site. We strongly suggest that BP conduct sampling for MBAS in the additional six monitoring wells named above. 3. The steadily increasing concentrations of TPHd in RO well AR/MW-18B and of TBA in trigger wells OW-4 B and C suggest that the oxygenation system may not be