Dam Safety FAQs
Frequently Asked Questions
I intend to build a pond, or farm pond on my property and wish to know the size limits of state jurisdiction?
What is the greatest rainfall event ever recorded in West Virginia?
What do you mean by hazard potential?
Q: I intend to build a pond, or farm pond, on my property and wish to know the size limits of state jurisdiction?
A: The jurisdiction size limits may be found in the Definition of a Dam. The great majority of private or farm ponds are too small for Dam Control and Safety Act jurisdiction, however, farm pond dams that are of jurisdiction size may meet an exemption. The exemption states that, if the purpose of the farm pond is primarily agricultural, the dam is exempt, providing there is no loss of life potential downstream. Loss of life potential is determined using a dam break analysis calculated by a licensed engineer. In some cases, the determination may be waived by Dam Safety if the downstream conditions make it obvious that loss of life is unlikely. Farm pond owners are cautioned that building their structure less than jurisdiction size is not a guarantee that they will not be held liable by the courts for any life or property damage resulting from a failure.
Q: What is the greatest rainfall event ever recorded in West Virginia?
A: West Virginia is in the meteorological record books for one of the world's greatest observed point rainfalls. On July 18, 1889, thunderstorms probably fed by moisture-laden tropical air from the Gulf of Mexico, dumped 19.5 inches of rain in two hours and 10 minutes at Rockport WV, just south of Parkersburg. The resulting flash floods roared through several villages, killing at least 19 people. Records show that the 18th, a Thursday, was humid and mild, with a temperature in the upper 70s. The darkening skies let loose about 8 p.m. R.D.J. Echols, a weather service observer, who lived in Rockport at the time described the deluge as "a terrific thunderstorm accompanied by vivid lightening."
Other reports said the Tygart Creek rose 22 feet in one hour, taking much of the village of Rockport with it. Barges were sunk, livestock and crops were lost, and logs from timber mills located along the creek became missiles that smashed through anything in their path. The rate of the Rockport storm exceeds that recorded in Smethport, Pa., on July 18, 1942, when 30 inches of rain fell in four hours. The Rockport storm nearly matches a rainfall rate recorded when a foot of water fell in Holt, Mo., in 42 minutes on June 22, 1947.
Although many people believe the greatest rainfalls are produced by hurricanes, these events argue otherwise.
From the Sunday Gazette-Mail: July 1989.
Q: What do you mean by hazard potential?
A: Dam Safety requires that each dam be evaluated for its hazard potential downstream. Hazard potential is not related to the structural integrity of a dam, but strictly to the potential for downstream flooding. The hazard potential evaluation places the dam in one of four classifications that are defined in the Dam Safety Regulations (47CSR34-3.5.b.) as follows:
Class 1 (High Hazard) dams are those dams located where failure may cause loss of human life or major damage to dwellings, commercial or industrial buildings, main railroads, important public utilities, or where a high risk highway may be affected or damaged. This classification must be used if failure may result in the loss of human life.
Class 2 (Significant Hazard) dams are those dams located where failure may cause minor damage to dwellings, commercial or industrial buildings, important public utilities, main railroads, or cause major damage to unoccupied buildings, or where a low risk highway may be affected or damaged. The potential for loss of human life resulting from failure of a Class 2 dam must be unlikely.
Class 3 (Low Hazard) dams are those dams located in rural or agricultural areas where failure may cause minor damage to nonresidential and normally unoccupied buildings, or rural or agricultural land. Failure of a Class 3 dam would cause only a loss of the dam itself and a loss of property use, such as use of related roads, with little additional damage to adjacent property. The potential for loss of human life resulting from failure of a Class 3 dam must be unlikely. An impoundment exceeding forty (40) feet in height or four hundred (400) acre-feet storage volume shall not be classified as a Class 3 dam. A waste disposal dam, the failure of which may cause significant harm to the environment, shall not be classified as a Class 3 dam.
Class 4 (Negligible Hazard) dams are dams where failure is expected to have no potential for loss of human life, no potential for property damage and no potential for significant harm to the environment. Examples of Class 4 dams include: dams across rivers, failure of which under any conditions will not flood areas above normal streambank elevations; dams located in the reservoir of another dam which, under any conditions, can contain water released by failure of the Class 4 dam; and dams in series where the toe of the Class 4 dam(s) is in close proximity to the reservoir of a dam which can contain failure of the Class 4 dam(s) under any condition. In considering a request for a Class 4 designation, the director may require written concurrence from the owner(s) of downstream dams that may be affected by failure of the Class 4 dam. Approval for use of this classification is vested in the director, and will be based on engineering evaluation of the dam(s) and downstream areas in question.