Indicator: Toxic Impairments in the Tidal Chesapeake Bay (2010-2024)

Access the Indicator Materials: - Analysis & Methods - Data File - Map Service This Indicator shows the percentage of Chesapeake Bay tidal segments that are fully or partially impaired under Clean Water Act 303(d) listings. It is based on the 2024 303(d) lists from Maryland, Virginia, Delaware, and the District of Columbia, as well as EPA data, and includes impairments associated with pollutants such as PCBs, chlorpyrifos, PFAS, metals, and priority organic contaminants. Waters are listed when measured or modeled contaminant levels exceed state water quality criteria, which can trigger TMDL development and related restoration actions. Note: This Indicator supported progress tracking toward the Toxic Contaminants Policy and Prevention Outcome in the original Chesapeake Bay Watershed Agreement, adopted in 2014. The Watershed Agreement and Toxic and Emerging Contaminants Outcome were revised in 2025.