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cha pter \/i 
Chlorophyll a Criteria 
Assessment Procedures 
STATE WATER QUALITY STANDARDS 
With publication of the April 2003 Ambient Water Quality> Criteria for Dissolved 
Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal Trib¬ 
utaries , the EPA provided the states with a recommended narrative (non-numerical) 
chlorophyll a criterion applicable to all of the Chesapeake Bay and its tidal tributary 
waters (Table VI-1) (U.S. EPA 2003). From 2004 through early 2006, Virginia and 
the District of Columbia adopted numerical chlorophyll a criteria for application in 
the tidal James River (Virginia) and across all the District’s jurisdictional tidal 
waters. Both jurisdictions determined that algae-related designated use impairments 
would likely persist in these tidal waters even after attainment of applicable 
dissolved oxygen and water clarity criteria. The technical information supporting 
adoption of numerical chlorophyll a criteria by Virginia and the District was 
published in the 2003 Chesapeake Bay water quality criteria document (U.S. EPA 
2003). Maryland and Delaware adopted narrative chlorophyll a criteria into their 
water quality standards regulations (Table VI-1). 
Table VI-1. Chesapeake Bay narrative chlorophyll a criteria. 
Concentrations of chlorophyll a in free-floating microscopic aquatic plants (algae) shall not 
exceed levels that result in ecologically undesirable consequences—such as reduced water 
clarity, low dissolved oxygen, food supply imbalances, proliferation of species deemed 
potentially harmful to aquatic life or humans or aesthetically objectionable conditions— 
or otherwise render tidal waters unsuitable for designated uses. 
Source: U.S. EPA 2003. 
chapter vi 
Chlorophyll a Criteria Assessment Procedures 
