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Al Jesena - 3 - 1 March 2000 Draft RI for OU#3 NCTS, Stockton Waste Characterization The Navy has not adequately characterized wastes at the site. In the case of OU #3, landfills are the primary source of contamination. Other sources include burn areas, contaminated soil, and sediment. Characterization involves the collection of data describing the physical and chemical characteristics of wastes present in the source area. Sampling and analysis of the landfills is necessary in order to determine the type of waste and chemicals present (EPA, 1988). One of the remedies proposed is to excavate and dispose of the waste off-site. Without knowing the quality of wastes, the Navy will not able to determine the threat to water quality and the economic viability of off-site disposal (e.g., hazardous waste disposal costs vs. municipal) or the health and safety hazards associated with excavation in the Feasibility Study (FS). Without knowing the type of waste/chemical containment provided by the landfills, the Navy cannot determine the potential remedies to address future releases if the landfills are not excavated. It is necessary to know the integrity of waste/chemical containment to determine the probability of a future release, how to monitor the release, and how to respond in a timely manner. The Navy has employed all the available sources to determine the content of the landfills except actual physical sampling. We would not be inclined to allow landfills to remain in-situ without knowing the content of the trenches. One cannot predict whether a landfill will eventually be a source of contamination or continue to be a source of contamination without knowing what may leach from the trenches, which are partially inundated with groundwater. Therefore, the Navy should propose a sampling and analysis plan for definitive characterization of waste in the landfills. Please also see our comment below on the Landfill Management Approach. Determine the Nature and Extent of Contamination Results of soil WET tests show that soluble constituents of concern potential concern (COPCs) as inorganics (e.g., pesticides, metals) and organics (e.g., petroleum hydrocarbons) have leached to groundwater. Background groundwater quality for inorganics have not been determined at NCTS, Stockton, nevertheless, the Navy repeatedly states that there are no impacts to groundwater because the metai(s) found above background"do not appear to be a concern." Surface and subsurface soil sampling results show inorganics and organics are widespread across the Landfill Area and not necessarily associated with landfills or hot spots. Information is manipulated using the VLEACHSM model. The Navy has used the model as a predictive tool to determine if a COPC can attenuate in the soil column as leachate and then further be attenuated by dilution and mixing in groundwater. Assumptions include: 1) there is no longer a source even though landfills are not lined, 2) the one slug of leachate does not increase/accumulate as it travels to depth through the vadose zon, and 3) the vadose zone is 21 feet thick based on Confining Unit 1 (a.k.a. shallow water-bearing zone Page B-26 of Appendix B states that, "the top of the shallow water-bearing zone beneath NCTS, Stockton(4 to 6 feet bgs)." This information is substantiated by Table 2.6, which shows groundwatc. elevations for each screened interval. In this regard, there is no attenuative capacity between contaminated soil and groundwater. r-