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Ms. Carol Campagna -3 - 27 March 2009 <br /> A Shell Stockton Terminal • <br /> through of TBA occurring in the treatment system. If Shell uses this option, Shell will need <br /> to ensure the TBA in the treatment system effluent meets permit limits. By 30 April 2009, <br /> Shell needs to submit a work plan to conduct an infiltration study. <br /> 3. We concur with Shell's proposal to implement a pilot test to evaluate AS/SVE as an <br /> alternative or in addition to DPE. We are concerned, however, that due to the variability in <br /> lithology and contaminant concentrations across the site, the results obtained from limiting <br /> AS/SVE testing to SA2 may not accurately indicate potential results in the other SAs. SA2 <br /> is underlain by siltier soils, compared to the sandy soils underlying SA1. Therefore, flow <br /> rates and vacuum responses may be correspondingly lower in SA2 compared to other <br /> areas of the Site. In addition, based on quarterly monitoring results, contaminant <br /> concentrations in SA2 have been historically higher than those encountered in other SAs. <br /> This indicates that mass removal rates attained during the SA2 AS/SVE Mot test may be <br /> higher than removal rates obtained from testing performed in other SAs. In addition, <br /> AS/SVE is considered to be less effective on the longer chained diesel range molecules <br /> compared to gasoline range molecules. Application of an additional technology may be <br /> required to complete the cleanup of diesel following the application of AS/SVE. By <br /> 1 November 2009, Shell needs to submit a report on the results of the AS/SVE pilot test <br /> including recommendations based on the outcome of the pilot test. <br /> 4. In the Annual Report, Shell requests permission to discontinue sampling for dissolved lead <br /> based on laboratory analytical results that are non-detect (ND). Although not recorded in <br /> the "Well Concentration" table in the QMRs, the laboratory analytical results recorded on <br /> Geotracker confirm that dissolved lead has been ND in sampling conducted for both the <br /> Semi-Annual and Annual Reports. Therefore, in accordance with footnote No. 6 of MRP <br /> R5-2005-0810, sampling for dissolved lead is no longer required. We concur with Shell's <br /> request to discontinue sampling for this constituent. <br /> 5. We cannot concur with Shell's request to discontinue treatment and extraction from MW-1. <br /> Although it is of limited effectiveness, groundwater extraction and treatment from MW-1 <br /> has resulted in the removal of 475 pounds of TPHg, benzene, and MTBE since treatment <br /> was implemented in April 2006. The baseline monitoring and testing that will be required to <br /> evaluate an alternate cleanup technology may delay immediate implementation of an <br /> optimized remedy. Thus, though limited, the benefits provided from running the MW-1 <br /> treatment system are preferable to having no remedial activities at the-Site in the interim. <br /> In summary, by 30 April 2009, please submit a work plan to monitor baseline concentrations <br /> and a work plan to conduct an infiltration study. By 1 November 2009, submit a report with <br /> the results of the AS/SVE pilot test. If you have any questions regarding this letter, you may <br /> contact meat (916) 464-4811 or betaylor@waterboards.ca.gov. <br /> BRIAN TAY OR, R.G. <br /> Engineering Geologist <br /> cc list on next page <br />