Mitre model

Arthur D. Little, Inc. (1981). Prepared Revisions to MITRE Model, Arthur D. Little, Inc., Cambridge, MA 02140. 

Hence risk assessment criteria must be established so that there can be developed a national priority list of the hazardous sites that require remedial action. EPA has adopted the Mitre Model for assessing the risks and ranking waste sites. There is some criticism of this model, and there are a number of as yet unanswered questions about its application. Formal cost/benefit analysis will not be used, and risk assessment will be on a case-by-case basis. EPA will thus be developing its knowledge base and procedures as it carries out the program. 

The Mitre Model. With the assistance of the Mitre Corporation, EPA has developed a model for assessing the risk and ranking superfund sites by Section 108. The Mitre Model is a simple, straightforward model which will rank sites largely on the basis of easily obtainable information. Five pathways of exposure (ground water, surface water, air, direct contact, and explosion) will be considered. The probability and magnitude of an adverse event will be estimated for each pathway to arrive at an overall risk estimate. 

Criticisms of the Mitre Model run from the fear that it will not be sufficiently precise or analytical to the concern that it makes no provision for utilizing extra information when it is readily available and is highly relevant. 

It is beyond the scope of this paper to examine the Mitre Model in detail. Rather, it is sufficient to note that there is merit to EPA s decision to adopt a practical risk assessment/pri-oritization approach. If a full risk analysis had to be conducted at every site, EPA would spend all its resources on assessment and would have difficulty knowing where to start the clean-up. On the other hand, the model must be flexible enough to take into account the information which does exist regarding a particular site so that the risk assessment can be as accurate as practically possible. 

Thus, once risk is taken into account in the prioritization process, the EPA has considerable latitude in devising methods and criteria for remedy selection, with the major substantive requirement being cost effectiveness under Section 105(7). Nevertheless, in many cases the Mitre Model will not produce a risk assessment adequate for remedy selection, and a more detailed assessment will be necessary. 

The Mitre Model and site ranking. EPA has developed a hazard assessment model (commonly called the Mitre Model) to help rank problem hazardous waste sites for potential Superfund response. The model is a relatively simple one, with minimal data requirements. The model is designed to provide scores for actual or potential impacts on health or the environment by three routes of exposure — groundwater, surface water, or air emissions — as well as by direct contact or fire and explosion. Parameters include toxicity, quantity, physical state and persistence of the waste at a site characteristics of a potential route (to groundwater, surface water, or air) of release of the wastes, e.g., soil permeability the mode of exposure or use of the natural resource, e.g., an aquifer or surface waters used for drinking water and the target of... 

Our experience has led us to doubt the utility of the Mitre Model for site ranking, beyond its use as a first cut screening device. The model scores for the Louisiana sites do not appear to correlate particularly well with other means of evaluating the relative ranking of problem seriousness, nor do they give any useful insight as to the type or extent of response that may be required. 

In discussions with EPA, we have noted that the Mitre Model does not appear to provide much ability to discriminate between the relative levels of risks posed by different sites, nor does it provide a basis for management decisions once a ranked list has been gathered. On the other hand, it is clear — again based on our experience — that the model would be too expensive to use as a screening device at any level, if it were made much more sophisticated than it is now. For example, the collection and analysis of data on the groundwater route can cost more than 100,000. Louisiana has done rather extensive site investigations for most of the sites listed with EPA, and the investments of resources have been substantial. We believe that, because of the simplicity of the Mitre Model, this poses problems of comparability with other ranked sites, where much less information may have been available. 

MITRE (1981). Site ranking model for determining remedial action priorities among uncontrolled hazardous substances facilities. The MITRE Co., McLean, VA 22102. 

Mitr ovic B, Par khrsorr J, Merrill JE (1996) An in vitro model of oli-goderrdrocyte destmcdorr by rritric oxide and its relevance to mul-dple sclerosis. Medrods 10 501—513. 

Kalagher, R. J. (1978). A Short Course on the SEAS Model, WP-13043. MITRE Corp, McLean, Virginia. 

Mitre JE, Takahashi RSM, Ribeiro CP Jr, Lage PEC (2010) Analysis of breakage and coalescence models for bubble columns. Chem Eng Sci 65 6089-6100... 

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