(a)  For the purposes of this Subchapter, dams shall be divided into three classes, which shall be known as class A (low hazard), class B (intermediate hazard), and class C (high hazard):

(1)           Class A includes dams located where failure may damage uninhabited low value non‑residential buildings, agricultural land, or low volume roads.

(2)           Class B includes dams located where failure may damage highways or secondary railroads, cause interruption of use or service of public utilities, cause minor damage to isolated homes, or cause minor damage to commercial and industrial buildings. Damage to these structures will be considered minor only when they are located in back water areas not subjected to the direct path of the breach flood wave; and they will experience no more than 1.5 feet of flood rise due to breaching above the lowest ground elevation adjacent to the outside foundation walls or no more than 1.5 feet of flood rise due to breaching above the lowest floor elevation of the structure, the lower of the two elevations governing. All other damage potential will be considered serious.

(3)           Class C includes dams located where failure will likely cause loss of life or serious damage to homes, industrial and commercial buildings, important public utilities, primary highways, or major railroads.

(b)  Classifications shall be proposed by the design engineer and are subject to approval by the Director.

(c)  Probable future development of the area downstream from the dam that would be affected by its failure shall be considered in determining the classification.

(d)  Dams will be subject to reclassification if the Director determines that the hazard potential has changed. Non‑structural provisions of adequately demonstrated effectiveness and reliability such as flood plain zoning, and early warning systems may be considered by the Director in making this determination.

(e)  When dams are spaced so that the failure of an upper dam would likely fail a lower dam, the consequence of the lower dam's failure shall be a determining factor for the upper dam's hazard classification.

(f)  In assigning a hazard classification where a bridge or roadway is the only damageable property below a dam, consideration shall be given to the possibility of loss of human life, indirect economic impact through loss of service, and direct cost of damage to the bridge or roadway.


History Note:        Authority G.S. 143‑215.31; 143‑215.34;

Eff. June 15, 1980;

Pursuant to G.S. 150B-21.3A, rule is necessary without substantive public interest Eff. December 23, 2017.