Section 69-05.2-20-03 - Performance standards - Dams and embankments constructed of or impounding coal processing waste - Design and construction1. The design of each dam and embankment constructed of coal processing waste or intended to impound the waste must comply with subsections 9 through 21 of section 69-05.2-16-09, modified as follows: a. The design freeboard between the lowest point on the embankment crest and the maximum water elevation must be at least three feet [91.44 centimeters]. b. The dam and embankment must have a minimum safety factor of 1.5 for a normal pool with steady seepage saturation conditions, and the seismic safety factor must be at least 1.2. c. The dam or embankment foundation and abutments must be designed to be stable under all conditions of construction and operation of the impoundment. Sufficient foundation investigations and laboratory testing must be performed to determine the safety factors of the dam or embankment for all loading conditions appearing in subdivision b and for all increments of construction. d. Each structure that meets the criteria of 30 CFR 77.216(a) must have sufficient spillway capacity to safely pass the probable maximum precipitation of a six-hour precipitation event, or greater event specified by the commission, when the impoundment is at high water elevation. 2. Spillways and outlet works must be designed to provide adequate protection against erosion and corrosion. Inlets must be protected against blockage. 3. Dams or embankments constructed of or impounding waste materials must be designed so that at least ninety percent of the water stored during the design precipitation event can be removed within a ten-day period. 4. For dams or embankments constructed of or impounding waste materials, at least ninety percent of the water stored during the design precipitation event must be removed within the ten-day period following the event. N.D. Admin Code 69-05.2-20-03
Effective August 1, 1980; amended effective May 1, 1990; May 1,1992; June 1, 1994.General Authority: NDCC 38-14.1-03
Law Implemented: NDCC 38-14.1-24, 38-14.1-25