4 Va. Admin. Code § 50-20-280
All new impounding structures regardless of their hazard potential classification, shall include a device to permit draining of the impoundment within a reasonable period of time as determined by the owner's licensed professional engineer. Existing drains on impounding structures shall be kept operational. When practicable, existing impounding structures shall be retrofitted with devices to permit draining.
§ 10.1-605 of the Code of Virginia.
Derived from VR625-01-00 § 5.5, eff. February 1, 1989; amended, Virginia Register Volume 24, Issue 25, eff. September 26, 2008.