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chapter | 
Introduction 
In April 2003, the U.S. Environmental Protection Agency (EPA) published the 
Ambient Water Quality> Criteria for Dissolved Oxygen, Water Clarity and Chloro¬ 
phyll a for the Chesapeake Bay and Its Tidal Tributaries (Regional Criteria 
Guidance) in cooperation with and on behalf of the six watershed states—New York, 
Pennsylvania, Maryland, Delaware, Virginia and West Virginia—and 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 recog¬ 
nized 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 Team—water quality stan¬ 
dards program managers and coordinators from the seven Chesapeake Bay 
watershed jurisdictions and EPA’s 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 attain¬ 
ment procedures into their states’ water quality standards regulations. 
This first EPA published addendum to the 2003 Ambient Water Quality Criteria for 
Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its 
Tidal Tributaries documents the resolution of and recommendations for addressing 
the following technical issues and criteria attainment procedures. 
• Guidance to the jurisdictions on where and when to apply the temperature-based 
open-water 4.3 mg liter 1 instantaneous minimum dissolved oxygen criteria 
required to protect the endangered shortnose sturgeon (Chapter 2). 
• Key findings published in the Endangered Species Act required EPA shortnose 
sturgeon biological evaluation of the potential impacts and benefits from publica¬ 
tion of the Regional Criteria Guidance (Chapter 3). 
chapter i 
Introduction 
