Water quality standards consist of three core components:  designated uses of a water body, criteria to protect designated uses, and antidegradation requirements to protect existing uses and high quality/high value waters.

Designated Uses

Designated uses are specified in the water quality standards regulation for each water body, whether or not they are being attained. All Virginia waters are designated for the following uses:

1. Recreational uses, such as swimming and boating
2. Propagation and growth of a balanced, indigenous population of aquatic life, including game fish
3. Wildlife
4. Production of edible and marketable natural resources, e.g., fish and shellfish

Should additional standards be needed to protect other uses as dictated by law (such as public water supply) or improved knowledge, they will be adopted.

At a minimum, uses are deemed attainable through the impositions of technology and performance based effluent limits and cost effective and reasonable best management practices for nonpoint source controls.

Criteria

Water quality criteria can include general narrative statements that describe good water quality and specific numerical concentrations that are known to protect aquatic life and human health. The criteria are adjusted as needed to reflect changes in law and science. Water quality criteria protect the designated uses of a water body. Water quality criteria can be numeric (e.g., the maximum pollutant concentration levels permitted in a water body) or narrative (e.g., a criterion that describes the desired conditions of a water body being “free from” certain negative conditions). The Water Quality Standards have both numeric and narrative criteria. These numerical and narrative criteria describe water quality necessary to protect designated uses such as swimming, drinking water, and the propagation and growth of aquatic life.

Antidegradation

One of the principal objectives of the Clean Water Act is to “maintain the chemical, physical and biological integrity of the Nation's waters.” Antidegradation requirements provide a framework for maintaining and protecting water quality that has already been achieved.

Virginia's antidegradation policy protects water quality at three levels or "tiers."

• Tier I specifies that existing instream water uses and the level of water quality to protect the existing uses shall be maintained and protected. This means that as a minimum, all waters should meet adopted water quality standards.
• Tier II protects water that is better than specified water quality standards. Only in limited circumstances may water quality be lowered in these waters.
• Tier III are exceptional waters where no new, additional or increased discharge of sewage, industrial wastes or other pollution are allowed. These waters must be specifically listed in the regulation.