In April 2003, the U.S. Environmental Protection Agency (EPA) published the Ambient Water Quality Criteria for Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal Tributaries (Regional Criteria Guidance) in cooperation with and on behalf of the six watershed statesNew York, Pennsylvania, Maryland, Delaware, Virginia and West Virginiaand the District of Columbia. The culmination of three years of work, the Regional Criteria Guidance document was the direct result of the collective contributions of hundreds of regional scientists, technical staff and agency managers and the independent review by recognized experts across the country. At the time of publication of the Regional Criteria Guidance document, a number of technical issues still remained to be worked through, resolved and documented. The Chesapeake Bay Water Quality Standards Coordinators Teamwater quality standards program managers and coordinators from the seven Chesapeake Bay watershed jurisdictions and EPAs Office of Water, Region 2 and Region 3, took on the responsibility on behalf of the Chesapeake Bay watershed partners to collectively work through these technical issues. The work on these issues was largely in support of the four jurisdictions with bay tidal waters who were formally adopting the published Chesapeake Bay water quality criteria, designated uses and criteria attainment procedures into their states water quality standards regulations.