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Mr. Maurice Benson <br /> February 11 , 2010 <br /> Page 4 <br /> DDJC Sharpe's PWs are continuing to draw the shallower TCE plume into <br /> deeper uncontaminated aquifers at those locations. In addition, the operating <br /> supply wells are drawing contaminants into the drinking water for several <br /> hundred people stationed at DDJC Sharpe and unnecessarily subjecting those <br /> workers to carcinogens due to the open exposure pathways of dermal, ingestion, <br /> and inhalation. DESJC should consider corrective actions to mitigate these <br /> above mentioned issues including permanent well replacement and relocation if <br /> necessary for the protection of human health and the environment. <br /> 6.) Page 4-16, section 4.6.5, Site P-5A: Soil vapor extraction is mentioned as the <br /> preferred remedial alternative for the unsaturated soils but the report fails to <br /> discuss the innovative technology of hydraulic fracturing and injection of EHC <br /> (carbon coated zero-valent iron substrate) slurry in an attempt to remediate <br /> volatile organic compounds (VOC) present in both saturated soil matrix and <br /> localized groundwater. DTSC recommends the report is modified to include a <br /> brief discussion of remedial efforts at Site P-5A as part of a concise <br /> administrative record and for public knowledge. <br /> 7.) Page 5-1, section 5.1, Revisions to Conceptual Site Model:DTSC notes that no <br /> discussion or information is provided on the persistent groundwater source P-5A <br /> and its effect on the current site model, including groundwater cleanup time <br /> projections. Additionally, Sites P-1E and P1-G in the South Balloon are showing <br /> remaining VOC contaminant mass in the saturated soil and groundwater <br /> requiring additional fieldwork efforts to remediate the remaining contaminant <br /> mass responsible for the groundwater plumes, more recently delineated by the <br /> 2007/2008 CPT fieldwork. The report should be modified to include the above- <br /> mentioned sites due to their effect on groundwater cleanup times and the <br /> necessary fieldwork efforts to remediate the persistent source of VOC to <br /> groundwater. <br /> 8.) Page 5-4, section 5.3.6, Recommended Revisions to Sampling Frequencies: <br /> DTSC wishes to engage DESJC and its contractor'in face-to-face discussions for <br /> the proposed sampling frequencies for wells part of the DDJC-Sharpe monitoring <br /> program. Based on past experiences, a face-to-face meeting provides all <br /> stakeholders with a hands-on opportunity to verify or refute proposed well <br /> sampling frequencies in an efficient manner with the goal of protection of human <br /> health and the environment. <br /> Conclusions <br /> DTSC has reservations with the proposed potable well (PW) sampling frequencies <br /> regardless of the new sampling logic presented. Concerns center around the <br /> representativeness of the guard well sampling in conjunction with the protection of <br />