Virginia Dam Hazard Classification
Virginia classifies dams by what happens downstream if they fail, not by how big they are. The criteria are in Virginia Impounding Structure Regulations, 4VAC50-20.
Virginia can regulate a six-foot dam, and puts a number on what counts as a major roadway: more than 400 vehicles AADT.
The classes
| Class | Criteria |
|---|---|
| High | Failure would cause probable loss of life or serious economic damage — residences, businesses, occupied structures, or major roadways. |
| Significant | Failure may cause loss of life or appreciable economic damage — frequently used facilities other than ordinary residences and businesses, or secondary roadways. |
| Low | Failure would result in no expected loss of life and no more than minimal economic damage. |
Why classification decides everything else
Classification is not an administrative label. It determines whether an emergency action plan is required, what design flood the spillway must pass, and how often the dam is inspected. Getting it wrong in either direction is expensive: too low and the owner is out of compliance, too high and they are designing to a storm the structure never needed.
Worked end to end for a real structure: the flood rise test that separates the middle tier from high hazard, and the breach analysis behind it.
Scope. General information about Virginia dam safety regulation, read from primary sources and current as of 2026-08-28. Not an engineering opinion about any specific structure and not legal advice. Requirements change when the legislature amends the Dam Safety Act or the rules are revised — confirm against the current text of Va. Code ยงยง 10.1-604 et seq. and Virginia Impounding Structure Regulations, 4VAC50-20, and contact the Virginia Soil and Water Conservation Board for a determination that binds.