Chapter 2 documents refinements to the procedures for defining Chesapeake Bay designated uses 
and expands the application of the deep-water seasonal fish and shellfish designated use to two 
Chesapeake Bay segments in Maryland's tidal waters. 
Chapter 3 documents refinements and additions to the previously published procedures for 
deriving biologically-based reference curves and recommendations for their application for 
Chesapeake Bay dissolved oxygen criteria assessments. 
Chapter 4 documents refinements and provides recommendations for the procedures assessing 
the previously published numerical Chesapeake Bay chlorophyll a criteria. 
Appendices to these three chapters provide more detailed documentation on derivation of the 
recommended refined criteria assessment procedures. 
This document represents the fifth formal addendum to the original 2003 Chesapeake Bay water 
quality criteria document. As such readers should regard the sections in this document as new or 
replacement chapters and appendices to the original published Bay Criteria report (U.S. 2003a). 
The criteria assessment procedures published in this addendum also replace and otherwise 
supersede similar criteria assessment procedures published in the 2004, 2007 and 2008 addenda 
(U.S. EPA 2003a, 2004a, 2007a, 2007b, 2008). Publication of future addenda by EPA on behalf 
of the Chesapeake Bay Program watershed jurisdictional partners is likely as continued scientific 
research and management applications reveal new insights and knowledge that should be 
incorporated into revisions of state water quality standards regulations in upcoming triennial 
reviews. 
LITERATURE CITED 
U.S. Environmental Protection Agency. 2003a. Ambient Water Quality Criteria for Dissolved 
Oxygen , Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal Tributaries 
(Regional Criteria Guidance). April 2003. EPA 903-R-03-002. Region III Chesapeake Bay 
Program Office, Annapolis, MD. 
U.S. Environmental Protection Agency. 2003b. Technical Support Document for Identification of 
Chesapeake Bay Designated Uses and Attainability. October 2003. EPA 903-R-03-004. Region 
III Chesapeake Bay Program Office, Annapolis, MD. 
U.S. Environmental Protection Agency. 2004a. Ambient Water Quality Criteria for Dissolved 
Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal Tributaries - 
2004 Addendum. October 2004. EPA 903-R-04-005. Region III Chesapeake Bay Program 
Office, Annapolis, MD. 
U.S. Environmental Protection Agency. 2004b. Technical Support Document for Identification of 
Chesapeake Bay Designated Uses and Attainability - 2004 Addendum. October 2004. EPA 903- 
R-04-006. Region III Chesapeake Bay Program Office, Annapolis, MD. 
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