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O�, • • Mr. Brian Taylor <br /> November 9,2007 <br /> CONESTO3A-ROVERS <br /> &ASSOCIATES <br /> Water Resources Control Board (State Water Board) Resolution No. 68-16 (the antidegradation policy) <br /> and State Water Board Resolution No. 9249. Based on these resolutions and the Basin Plan, cleanup <br /> levels for groundwater are background concentrations. If background is not technically or economically <br /> feasible to achieve, cleanup levels must be consistent with WQOs. Soil cleanup levels are those levels <br /> which will not degrade groundwater quality and may be determined by use of the Designated Level <br /> Methodology." <br /> Response: As presented in the FS, "Although significant reductions in groundwater concentrations of <br /> CDCs can be attained in localized (source) areas by various remedial alternatives, attainment of the <br /> approved groundwater clean-up levels on a site-wide basis is considered to be technically and/or <br /> economically infeasible. Thus, consistent with Basin Plan guidance, proposed groundwater clean-up is <br /> limited to that which is technically and economically feasible, and will focus on source removal/control." <br /> Based on this statement, and technical expertise with remediating sites in similar settings (i.e., active <br /> facilities with site constraints that prevent access to impacts, low permeability conditions, complex but <br /> stable plume conditions, etc.)it is highly unlikely that WQOs can be reached in the most highly impacted <br /> areas. However, it is likely that significant concentration reductions can be achieved in the accessible <br /> portions of the three source areas should DPE activities be implemented as proposed within the FS. If <br /> the Regional Board does not consider source removal with long-term monitoring a sufficient/appropriate <br /> remedy for this site, Shell would like to explore the option of a Containment Zone approach (in <br /> accordance with Resolution 92-49 of Water Code Section 13304). <br /> Page 3,Item 5: "We concur with Shell's proposal to discharge the treated DPE effluent to the vacant lot <br /> north of the facility, if Shell enrolls in Order No. R5-2003-0044 and meets all the requirements of that <br /> Order. We agree that implementation of this disposal method will depend on the results of infiltration <br /> testing to determine capacity of the soil in this area. However, we are concerned about break-through of <br /> TBA occurring in the treatment system. If Shell uses this option, Shell will need to ensure the TBA in <br /> the treatment system effluent meets permit limits." <br /> Response: Similar to the RWQCB, Shell is also concerned about the potential for TBA break-through in <br /> the treatment system effluent. Because the permit limits for discharge of treated water in this area are <br /> very stringent, Shell is extremely concerned about attempting to construct, operate and maintain a <br /> treatment system that maintains compliance with the stringent discharge limitations associated with <br /> NPDES, discharge to land, or the City of Stockton POTW permits. Consequently, it is Shell's technical <br /> opinion that a more favorable permit is necessary or we can not agree to install, operate, and maintain a <br /> system in this area. <br /> 1729 4 <br /> Worldwide Engineering, Environmental, Construction, and IT Services <br />