Developing Water Quality Criteria for Suspended and Bedded Sediments – Illustrative Example Application

The U. S. EPA's Framework for Developing Suspended and Bedded Sediments (SABS) Water Quality Criteria (SABS Framework) provides a consistent process, technical methods, and supporting materials to enable resource managers to develop ambient water quality criteria for one of the most commonly cited causes of water quality impairment. The SABS Framework recognizes that SABS occur naturally but are often altered by human activities and cause adverse impacts to Designated Uses of waterbodies (e. g., recreation, drinking water supply, aquatic life). It also recognizes that SABS criteria values must be customized for different waterbody types, different natural ambient levels of sediment, and various local or regional conditions. An important aspect of the SABS Framework is that it ties SABS criteria to levels that protect Designated Uses as described in the U. S. Clean Water Act. The process is nationally consistent, yet allows local implementation. The SABS process allows flexibility in the choice of assessment endpoints, measures, Designated Uses to protect, and analysis tools. The SABS Framework describes multiple technical methods and examples for measuring, classifying, and associating various levels of SABS with Designated Uses. A hypothetical application using data typical of the U. S. mid-Atlantic streams is used to illustrate the criteria development process. The mid-Atlantic stream data are further classified for heavily forested surrounding drainage. This application is used to illustrate the ability of the SABS Framework to refine SABS criteria for application to a subset of waters that are of special interest. Candidate criteria values were identified using a weight-of-evidence approach for demonstration of associations between levels of SABS and their impacts on Designated Uses. The process for deriving SABS criteria is intended to be integrative and to allow incorporation of information from different data sets and different perspectives, thereby increasing confidence in the selected criteria values. The generic criteria development process described in the SABS Framework is adaptable to development of other criteria types beyond SABS.