in 2020, some parts of the Chesapeake Bay were not impaired and thus were not included on the dirty waters list
Source: Virginia Department of Environmental Quality (DEQ), Summary of All Impairment Causes in Virginia's Bay Waters
Section 303(d) of the Clean Water Act requires each state to identify its impaired waters, those rivers, lakes and estuaries which do not meet the six primary designated uses. The Virginia Department of Environmental Quality (DEQ) inckudes a Total Maximum Daily Load (TMDL) Priority List for impaired waters in the biennial report to the Federal government.
The six designated uses in Virginia are:1
The water monitoring strategy in Virginia is to assess one third of the state's 1,247 sub-watersheds every two years. That cycle results in each 12-digit (6th Order) sub-watershed being re-evaluated every six years.
The Environmental Protection Agency and the Virginia Department of Environmental Quality categorize rivers, lakes and estuaries that meet water quality standards for the six designated uses as Category 1 waters.
In Category 2 waters of the designated uses are supported, but data is inadequate to etermine if all uses are supported. For example, if no water quality standard exists for a specific pollutant, then the waters are included in Category 2. If there is inadequate information to determine if any designated uses are met, the waters are placed in Category 3.
Category 4 waters are impaired or threatened, but a new TMDL is not required. The pollution that damages such waters is from natural sources, or is being addressed by actions other than a TMDL (such as requirements in a stormwater permit) that will correct the problem within two years. In addition, impaired tributaries to waters where the impairment is already being addressed by a previous TMDL are placed in Category 4 as well.
Category 5 waters are impaired or threatened by pollution that makes the stream, lake or estuary unsuitable for one or more designated uses, and require a TMDL to be developed.2