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cha pter 
Introduction 
Since the signing of the multijurisdicational Chesapeake 2000 agreement, the U.S. 
Environmental Protection Agency (EPA), in cooperation with its six watershed State 
partners and the District of Columbia, has developed a series of water quality criteria 
guidance documents in accordance with Section 117b of the Clean Water Act. 
Chesapeake Bay regional water quality criteria were developed and adopted into 
state water quality standards regulations protective of living resources and their habi¬ 
tats. Five aquatic life tidal-water designated uses were defined by the partners (U.S. 
EPA 2003a) apportioning the Chesapeake Bay and its tidal tributaries into appro¬ 
priate habitats: 
• Migratory fish spawning and nursery habitat; 
• Open water fish and shellfish habitat; 
• Deep-water seasonal fish and shellfish habitat; 
• Deep-channel seasonal refuge habitat; and 
• Shallow-water Bay grass habitat 
Ambient Water Quality Criteria for Dissolved Oxygen, Water Clarity and Chloro¬ 
phyll a for the Chesapeake Bay and Its Tidal Tributaries (Regional Criteria 
Guidance) April 2003 has been the foundation document defining Chesapeake Bay 
water quality criteria and recommended implementation procedures for monitoring 
and assessment (U.S. EPA 2003a). The Technical Support Document for Identifica¬ 
tion of Chesapeake Bay Designated Uses and Attainability October 2003 defined the 
five tidal water designated uses to be protected through the published Bay water 
quality criteria (U.S. EPA 2003b). Six addendum documents have been published 
since April 2003 addressing detailed issues involving further delineation of tidal 
water designated uses (U.S. EPA 2004a), Chesapeake Bay Program analytical 
segmentation schemes (U.S. EPA 2004c, 2005), detailed criteria attainment and 
assessment procedures, (U.S. EPA 2004b, 2007a), and Chesapeake Bay numerical 
chlorophyll a criteria (2007b). 
The detailed procedures are assessing attainment of the Chesapeake Bay water 
quality criteria advanced through the collective EPA, States and District of Columbia 
partner efforts to develop and apply procedures that incorporate, at the most 
advanced state, magnitude, frequency, duration, space and time considerations with 
chapter i 
Introduction 
