Evaluation of a Terrestrial Foodweb Model to Set Soil Cleanup Levels

The Washington State Department of Ecology (Ecology) is revising the Model Toxics Control Act (MTCA: WAC 173-340-7490 to 7494) to include terrestrial food pathways in an ecological risk evaluation and to set cleanup levels. One of the key provisions of the ecological risk assessment approach proposed by Ecology is a generic simplified "foodweb" model that would be used to set cleanup levels. The terrestrial model is based on four feeding guilds and default species are the earthworm, shrew, vole, and robin. The use of a foodweb model implies that the results should in some way be descriptive of the ecosystem being evaluated. Any decision criterion (e.g., a benchmark or cleanup level) should be site-specific, and based on species present at the site. The default species are not representative of the fauna in the native shrub-steppe ecosystem of the Hanford Site. Therefore, the use of species not present at the site to set soil cleanup levels seems flawed. Alternative species for the four feeding guilds have been selected. Species specific exposure parameters were developed from the literature.