Overview of Superfund Program's Dioxin Tool Box
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The Office of Superfund Remediation and Technology Innovation released a suite of technical tools to assist Superfund site managers in the sampling and analysis of dioxin contaminated soils in 2011. The "Dioxin Tool Box," contains five different technical documents addressing key issues related to incremental composite sampling (ICS), capabilities of the Non-Routine Analytical Services (NRAS) contract (for both PCB congeners and dioxin-like materials) and dioxin-contaminated soils management. Two of the tool box's resources provide technical information on the use of ICS to evaluate dioxin-contaminated soil in a manner consistent with the requirements of the Unified Federal Policy for Implementing Environmental Quality Systems. ICS differs from traditional sampling in several key ways. Traditional field sampling often takes a relatively few small samples from across a large area with the samples spread far apart. Statistics are used to infer the nature and extent of contamination for that area from these widely spaced individual samples. In contrast, ICS first defines the size of the area to be covered, which is usually smaller than typical field areas. Incremental sampling then takes many small samples, called increments (usually 30 or more), from across the defined area that may be as small as a residential lot. Because there are so many increments, the spacing between them is much less than the spacing between traditional samples, ICS catches both high and low concentrations across the area. The increments are then pooled (or composited) into a single sample that is submitted for analysis. The ICS data results confidently represent the concentration for that defined area; no statistics are required.
ICS melds the principles and strategies of incremental sampling with the flexibility and capabilities offered by composite sampling. It is the most cost-effective way to get an accurate estimate of the mean concentration for a defined area, which is called a decision unit (DU). Composite sampling can supplement incremental sampling to search for “hot spots,” to clear several DUs at once with potentially only one analysis, or to improve the representativeness of discrete samples. These sampling strategies are useful for a wide range of contaminants, not just dioxins.
The tool box also contains information regarding the Superfund programs Non Routine Analytical Services (NRAS) capabilities. Because measurements of certain dioxins/furans and dioxin-like polychlorinated biphenyl (PCB) congeners are not analyses conducted under Superfunds Contract Laboratory Program, they are managed as part of the NRAS. The two NRAS fact sheets include a description of the NRAS services, how those services are requested, data uses, target compounds and detection limits and quality assurance and quality control.
The final tool in the Dioxin Tool Box addresses proper management of dioxin contaminated soils when carrying out remedial actions. The “Fact Sheet on the Management of Dioxin Contaminated Soils” provides guidance to EPA regional staff on managing dioxin contaminated soils in a fashion consistent with the Comprehensive Environmental Response, Compensation and Liability Acts overall remedy selection framework, the National Oil and Hazardous Substances Pollution Contingency Plan and other relevant Superfund program guidance.