32 
developing an accounting of error in the assessment process. Research has been 
underway over the past years to develop such a methodology. The technical details 
are challenging, however, and research has not yet led to a solution. Progress has 
occurred over the last year; a statistical framework could possibly be developed for 
adoption into the state’s water quality standards in upcoming 303(d) listing cycles. 
Other refinements may be developed for monitoring programs and the interpolation 
procedures. The EPA encourages states to prepare for adopting such refinements to 
their criteria assessment procedures into future regulations. 
Reference curves provide a second example of expected refinements. As more data 
are collected, the capability for better defining the amount and pattern of criteria 
exceedance that the system can withstand will continually improve. While major 
changes to the reference curves are not expected, updating the reference curves with 
additional data will improve the states’ ability to assess Chesapeake tidal waters 
accurately. With the prior agreement of the watershed jurisdictions, the EPA will 
update the reference curves with new data and publish the revised curves in future 
criteria document addenda. The jurisdictions will then need to adopt the new refer¬ 
ence curves into their water quality standards regulations through their regular 
triennial review processes. 
LITERATURE CITED 
Chesapeake Bay Program. 1989. Chesapeake Bay Monitoring Program Atlas-Volume I: 
Water Quality and Other Physiochemical Monitoring Programs. CBP/TRS 34/89. U.S. Envi¬ 
ronmental Protection Agency Chesapeake Bay Program Office, Annapolis, MD. 
U.S. Environmental Protection Agency (U.S. EPA). 2003a. Ambient Water Quality’ Criteria for 
Dissolved Oxy’gen, Water Clarity> and Chlorophyll a for the Chesapeake Bay and Its Tidal Trib¬ 
utaries. EPA 903-R-03-002. Region III Chesapeake Bay Program Office, Annapolis, MD. 
U.S. Environmental Protection Agency. 2003b. Technical Support Document for Chesapeake 
Bay Designated Uses and Attainability. 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 Chesapeake Bay and its Tidal Tributaries-2004 
Addendum. EPA 903-R-04-005. Region III Chesapeake Bay Program Office, Annapolis, MD. 
U.S. Environmental Protection Agency. 2004b. Chesapeake Bay Program Analytical 
Segmentation Scheme: Revisions, Decisions and Rationales 1983-2003. EPA 903-R-04-008. 
CBP/TRS 268/04. Region III Chesapeake Bay Program Office, Annapolis, MD. 
U.S. Environmental Protection Agency. 2004c. Technical Support Document for Chesapeake 
Bay Designated Uses and Attainability-2004 Addendum. EPA 903-R-04-006. Region III 
Chesapeake Bay Program Office Annapolis, Maryland. 
U.S. Environmental Protection Agency. 2005a. Chesapeake Bay Program Analytical 
Segmentation Scheme: Revisions, Decisions and Rationales 1983-2003. 2005 Addendum. 
EPA 903-R-05-004. CBP/TRS 278-06. Region III Chesapeake Bay Program Office, 
Annapolis, MD. 
U.S. Environmental Protection Agency. 2005b. Guidance for 2006 Assessment, Listing and 
Reporting Requirements Pursuant to Sections 303(d) and 314 of the Clean Water Act. 
Watershed Branch, Assessment and Watershed Protection Division. Office of Wetlands, 
Oceans and Watersheds, Office of Water, U.S. EPA, Washington, D.C. 
chapter iii 
Application of Chesapeake Bay Water Quality Criteria Assessment Procedures 
