2 
biologically-based reference conditions and cumulative frequency distributions. As 
a rule, the best test of any new method or procedure is putting it to work with stake¬ 
holder involvement. Through the work of its Criteria Assessment Protocols 
Workgroup, the Chesapeake Bay Program has an established forum for resolving 
details of baywide criteria assessment procedure development and implementation. 
This addendum document provides previously undocumented features of the present 
procedures and refinements and clarifications to the previously published Chesa¬ 
peake Bay water quality criteria assessment procedures. 
Chapter 2 documents the most recent Chesapeake Bay 92-segment scheme used for 
criteria assessment. 
Chapter 3 documents refinements and additions to the procedures for assessing the 
previously published Chesapeake Bay dissolved oxygen criteria. 
Chapter 4 documents refinements and additions to the procedures for assessing the 
previously published Chesapeake Bay water clarity and SAV criteria and deter¬ 
mining attainment of the shallow-water designated use. 
Chapter 5 documents refinements and additions to the procedures for assessing the 
previously published Chesapeake Bay chlorophyll a criteria. 
Appendices to the chapters include more detailed documentation on derivation of the 
criteria assessment procedure elements and step-by-step through procedures for 
assessing criteria. 
This document represents the fifth formal addendum to the 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 
report. The criteria assessment procedures published in this addendum also replace 
and otherwise supersede similar criteria assessment procedures originally published 
in the 2003 Regional Criteria Guidance and the 2004 and 2007 addenda (U.S. EPA 
2003a, 2004a, 2007a, b). Publication of future addendums 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 Identifica¬ 
tion of Chesapeake Bay Designated Uses and Attainability. October 2003. Region III 
Chesapeake Bay Program Office. EPA 903-R-03-004. Annapolis, MD. 
chapter i 
Introduction 
