Development of Draft MTCA Model Remedy for Abandoned Mine Sites
Washington State Department of Ecology
Hart Crowser assisted the Washington State Department of Ecology by preparing a draft guidance document for cleaning up abandoned/inactive metal mine sites using a streamlined, model-remedy approach. Under the Model Toxics Control Act (MTCA), the state’s cleanup regulation, model remedies may be developed and implemented at certain well-defined sites without the need for conducting a site-specific feasibility study or disproportionate cost analysis. Hart Crowser evaluated regulatory constraints applicable to upland abandoned/inactive metal mine sites where waste rock and/or tailings are the main contaminant sources and direct contact/soil ingestion are the main exposure routes to humans and terrestrial organisms. As part of this project, Hart Crowser:
- Outlined decision points needed for two model remedies, including excavating/disposing of mine wastes off-site and consolidating/capping mine wastes on site.
- Identified data requirements and site characteristics for which of these model remedies would be appropriate, or whether both would be appropriate.
- Identified Applicable or Relevant and Appropriate Requirements (ARARs) and substantive permit requirements that would likely need to be met in order to implement a model remedy.
- Conducted a generic Feasibility Study and Disproportionate Cost Analysis to compare the conditions under which one or both of the model remedies could be selected as a cleanup action under MTCA.
- Outlined a streamlined approach to conducting a Terrestrial Ecological Evaluation under MTCA that would be used to determine if one or both of the model remedies could be selected as a cleanup action under MTCA.
- Presented a framework for conducting a Net Environmental Benefit Analysis that could be used to support a “no action” cleanup decision at sites where cleanup activities could result in more environmental harm than benefit.