U.S. EPA has recently completed a national assessment of sediment contamination in waters throughout the United States. As part of this assessment, U.S. EPA compiled existing sediment chemistry, sediment toxicity, and fish tissue residue data from ind ividual monitoring stations throughout the nation. Tier 1 monitoring stations indicate a higher probability of association with adverse effects, and Tier 2 stations indicate lower to intermediate probability of adverse effects. Other monitoring stations do not indicate probability of association w ith adverse effects. The IWI distinguishes between watersheds which have no data and those that have too little data to draw conclusion s from.
Additional data needs to be collected assessing sediment conditions at more locations.
Plans to Improve this Data Layer To improve the data quality of this data layer, U.S. EPA will continue to coordinate with U.S. EPA regional offices, States, Tribes, and others to compile and identify additional data. U.S. EPA was specifically mandated by the Water Resources Development Act to compile all existing information on the quantity, chemical and physical composition, and geographic location of pollutants in aquatic sediment, including identification of those sediments which are contaminated. As part of this effort, U.S. EPA collects and evaluates sediment and fish tissue data from State, U.S. EPA regional, and other monitoring programs.