Environmental Cleanup at Navy Facilities Risk-Based Methods (1999) / Chapter Skim
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3 Strengths and Weaknesses of Risk-Based Methodologies
3 Strengths and Weaknesses of Risk-Based Methodologies
Pages 68-82
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From page 68... ...
The major characteristics of the ASTM RBCA methodology and the CERCLA process (including the EPA's Risk Assessment Guidance for Superfund and Soil Screening Guidance) are compared in an illustrative matrix that reveals their similarities and differences.
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From page 69... ...
In keeping with recent interagency guidance, the committee defines "contamination left in place" as "hazardous substances, pollutants, or contaminants remaining at the site above levels that allow for unlimited use and unrestricted exposure" (Air Force/Army/Navy/EPA, 1998~. Risk-based methodologies are more likely to leave contamination in place because they rely on engineering controls and institutional controls as alternatives to treatment.
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From page 70... ...
(It should be noted that all approaches that leave some contamination in place, including technology-based approaches, are characterized by uncertainty.) Uncertainty affects the risk assessment calculations, as well as the efficacy of treatment technologies, engineering controls, and institutional controls.
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From page 71... ...
. The Soil Screening Guidance and the ASTM RBCA standard guides are both tiered approaches in which generic cleanup levels are replaced with site-specific cleanup levels as more data become available.
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From page 74... ...
Large Small apRBCA = petroleum RBCA, cRBCA = chemical RBCA
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From page 75... ...
The ASTM RBCA methodology facilitates the prioritization of sites for cleanup. Table 1 in petroleum RBCA explains the initial classification of sites based on immediate, short-term, long-term, or no demonstrable risk to human health and the environment and prescribes response actions for each site category.
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From page 76... ...
How the Weaknesses of a Risk-Based Approach Are Manifested in ASTM RBCA Like other risk-based methodologies that leave contamination in place, the ASTM RBCA standard guides suggest remedial options that include combinations of treatment technologies, engineering controls, and institutional controls. All of the negative consequences of remedies that rely on institutional controls will pertain to cleanups done under RBCA.
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From page 77... ...
This figure constitutes a significant weakness of the RBCA methodology if it is interpreted to mean that sites can be closed with no further action, rather than being monitored for some period of time to document that relevant exposure pathways remain incomplete. The potential for risk-based methodologies to discourage development of innovative technologies for source removal has been widely discussed since publication of the ASTM petroleum RBCA standard guide (Hazardous Waste News, 1998; Thompson, 1997~.
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From page 78... ...
what should be done to apply the frameworks successfully (ASTM, 1998~. The lack of public involvement called for during RBCA implementation is a weakness of the ASTM standard guides, particularly petroleum RBCA.
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From page 79... ...
The EPA has not developed a similar tiered approach for ground water because remedial options under CERCLA must comply with ARARs, which often specify maximum contaminant levels for ground water. It is true that many states have devised generic screening levels for soil and ground water contamination that are similar to RBCA
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From page 80... ...
Thus, the different methods for considering ground water and soil contamination, and the variability between state programs that may or may not use generic screening levels, complicate the CERCLA process relative to ASTM RBCA, and make CERCLA less streamlined and systematic. Another general strength of risk-based methodologies not clearly apparent in the CERCLA process is the prioritization of sites.
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From page 81... ...
Generic screening levels for soil and ground water are available only in some states and tend to be highly variable. Finally, the National Contingency Plan clearly states that institutional controls are a last choice for remedial options under CERCLA and should be considered only in combination with containment strategies.
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From page 82... ...
Memorandum dated 12/1/95 from Ned Butler, staff toxicologist, to Ted Rauh, deputy director, Hazardous Waste Management Program. California State Water Resources Control Board.
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