Laserfiche WebLink
i _ <br /> She--- ll Stockton Terminal • 3 28 February 2007 <br /> A <br /> be attained. If the existing GWE cannot be optimized, an alternate remedial technology <br /> must be implemented to address the groundwater pollution at this site. <br /> 2. Total extractable petroleum hydrocarbons (TEPH) and TBA were detected in deep well <br /> DW-2 at concentrations of 140 pg/L and 17 pg/L respectively. In addition, TPHd was <br /> detected in a sample obtained from the furthest downgradient well, MW-28 at 100 pg/L. <br /> These observations indicate that COCs at the site are neither laterally nor vertically <br /> delineated. Complete delineation of plume extents, is preferred prior to initiating remedial <br /> activities to ensure that the selected remedial technology is appropriate, as well as to <br /> ensure that the capture zone provided by the proposed system is adequate. Additional <br /> investigation is necessary in order to define lateral and vertical extents of the COC plumes <br /> at this site. <br /> 3. On 13 July 2004, Regional Water Board staff provided concurrence with an 8 July 2004 FS <br /> Work Plan prepared by RETEC on behalf of Shell. There is no documentation however, <br /> that a FS was submitted to us. By 27 April 2007, Shell must submit a FS that provides an <br /> evaluation of at least three remedial alternatives, and selects one remedial technology, for <br /> remediation of the groundwater underlying this Site. The FS must be prepared in <br /> accordance with the attached guidance. Further, and as discussed by all attendees at our <br /> 8 February 2007 meeting, the selected technology evaluation must address cleanup of, at <br /> a minimum, the two identified hot spots, near the Truck Loading Ramp and aboveground <br /> storage tank No. 14. We also recommend that the FS include a remedial investigation (RI) <br /> Work Plan to complete lateral and vertical plume delineation. The results of the RI <br /> investigation may be submitted along with Remedial Action Plan (RAP) once the results of <br /> the RI are available. <br /> 4. Based on our discussions during the 8 February 2007 meeting Shell disclosed that they <br /> had determined that oxygen injection is infeasible due to the fine-grained sediments <br /> underlying the site. Shell also acknowledged that MNA is infeasible due to the high COC <br /> concentrations in the subsurface. Therefore, it is appropriate to exclude evaluations from <br /> the RI/FS that declare of these two remedial alternatives to be infeasible at this Site. We <br /> recommend that the RI/FS be also reviewed by Mr. Daniel F. Walsh of Shell's Soil and <br /> Groundwater Management group to ensure that the appropriate internal approval is <br /> completed prior to submittal to the Regional Board. <br /> 5. Also, during the 8 February 2007 meeting all parties agreed that a human health risk <br /> assessment (HHRA) was needed. The HHRA is to address the residual hydrocarbon <br /> mass, remaining in soil and groundwater beneath your site, that may actually pose a threat <br /> to human health. The assessment shall evaluate both Baseline Carcinogenic Risk and <br /> Baseline Toxic Effects for both residential and commercial receptors. You are to evaluate <br /> for both direct dermal contact and volatilization to indoor air exposure scenarios, and all <br /> constituent concentrations detected in soil within the top 10 feet of soil are to be <br /> considered when evaluating for direct dermal contact. A one-in-a-million target risk level <br /> and a target hazard quotient of one are to be used. <br /> 6. During the 8 February 2007 meeting, Regional Water Board staff requested a Site visit with <br /> shell representatives. On the day this letter was prepared we had received no confirmation <br />