North Dakota Administrative Code
Title 89 - Water Commission
Article 89-04 - Water Management Plans for Surface Coal Mining Operations
Chapter 89-04-10 - Dams Constructed of or Impounding Waste Material
Section 89-04-10-02 - Construction of dams

a. Design shall be based on the flood from the probable maximum precipitation event unless the permittee shows that the failure of the impounding structure would not cause loss of life or severely damage property or the environment, in which case, depending on site conditions, a design based on a precipitation event of no less than hundred-year frequency may be approved by the state engineer.

b. The design freeboard distance between the lowest point on the embankment crest and the maximum water elevation shall be at least five feet [1.52 meters] to avoid overtopping by wind and wave action.

c. Dams shall have minimum safety factors as follows:

d. The dam, foundation, and abutments shall be stable under all conditions of construction and operation of the impoundment. Sufficient foundation investigations and laboratory testing shall be performed to determine the factors of safety of the dam for all loading conditions in subdivision c and for all increments of construction.

e. Seepage through the dam, foundation, and abutments shall be controlled to prevent excessive uplift pressures, internal erosion, sloughing, removal of material by solution, or erosion of material by loss into cracks, joints, and cavities. This may require the use of impervious blankets, pervious drainage zones or blankets, toe drains, relief wells, or dental concreting of jointed rock surface in contact with embankment materials.

f. Allowances shall be made for settlement of the dams and the foundation so that the freeboard will be maintained.

g. Impoundments created by dams of waste materials shall be subject to a minimum drawdown criteria that allows the facility to be evacuated by spillways or decants of ninety percent of the volume of water stored during the design precipitation event within ten days.

h. During construction of dams subject to this section, the structures shall be periodically inspected by a registered professional engineer to ensure construction according to the approved design. On completion of construction, the structure shall be certified by a registered professional engineer experienced in the field of dam construction as having been constructed in accordance with accepted professional practice and the approved design.

General Authority: NDCC 28-32-02, 61-02-11, 61-03-13

Law Implemented: NDCC 61-02-14