This report describes the accumulation of chemical contaminants in river, lake, ocean, and estuary bottoms and includes a screening-level assessment of the potential for associated adverse effects on human and/or environmental health. The United States Environmental Protection Agency (EPA) prepared this report to Congress in response to requirements set forth in the Water Resources Development Act (WRDA) of 1992. WRDA directed EPA, in consultation with the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Army Corps of Engineers (USACE), to conduct a comprehensive national survey of data regarding the quality of aquatic sediments in the United States. Section 503(a) of WRDA required EPA to 'compile all existing information on the quantity, chemical and physical composition, and geographic location of pollutants in aquatic sediment, including the probable source of such pollutants and identification of those sediments which are contaminated....' It further required EPA to 'report to the Congress the findings, conclusions, and recommendations of such survey, including recommendations for actions necessary to prevent contamination of aquatic sediments and to control sources of contamination.' In addition, Section 503(b) of WRDA requires EPA to conduct a comprehensive and continuing program to assess aquatic sediment quality. This program must establish methods and protocols for monitoring the physical, chemical, and biological effects of pollutants in aquatic sediment and of contaminated sediment. EPA submitted the first Report to Congress (EPA-823-R-97-006) on January 7, 1997.