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36.14.501    HIGH-HAZARD DAM DESIGN CRITERIA

(1) Designs for construction of high-hazard dams must conform to accepted practices and procedures of the engineering profession.

(2) Design as well as preparation of the construction plans and specifications must be prepared by or under the direction of an engineer experienced in dam design and construction.

(3) An earthfill dam must be safe and stable during all phases of construction and operation of the reservoir. To accomplish this, the following criteria must be met:

(a) the embankment must be safe against overtopping during occurrence of the inflow design flood by the provision of sufficient spillway and outlet works capacity;

(b) the slopes of the embankment must be stable during construction and under all conditions of reservoir operation, including rapid drawdown of the reservoir;

(c) the embankment must be designed so as not to impose excessive stresses upon the foundation;

(d) seepage flow through the embankment, foundation, and abutments must be controlled so that no internal erosion or piping takes place and so there is no sloughing in the area where the seepage emerges;

(e) the embankment must be safe against overtopping by wave action;

(f) the upstream slope must be protected against erosion by wave action, and the crest and downstream slope must be protected against erosion due to wind and rain;

(g) the design must be such that the most severe earthquake that can be reasonably anticipated will not cause catastrophic failure and loss of life; and

(h) construction of the dam and its appurtenants must be constructed utilizing proper methods and control.

(4) Except as otherwise specified in ARM 36.14.501 to 36.14.504, concrete dams must be designed and constructed in accordance with principles at least equivalent to United States bureau of reclamation Design of Small Dams to its specified limits, or Design of Gravity Dams and Design of Arch Dams.

(5) Except as otherwise specified in ARM 36.14.501 to 36.14.504, earth dams retaining a flood water capacity of less than 12,500 acre-feet or a total capacity of less than 25,000 acre-feet measured to the primary emergency spillway must be designed and constructed in accordance with principles at least equivalent to United States soil conservation service TR-60, Earth Dams and Reservoirs. In this paragraph, total capacity means the total volume of space available for water and sediment upstream from a dam below the elevation at which discharge begins in the primary emergency spillway. In this paragraph, floodwater detention capacity is the capacity between the crest of the principal spillway and the elevation at which discharge begins in the primary emergency spillway sediment.

(6) Except as otherwise specified in ARM 36.14.501 to 36.14.504, earth dams greater than the limits specified in (5) must be designed and constructed at least equivalent to the United States bureau of reclamation Design of Small Dams to its limit of a 50-feet dam height, and to the corps standard beyond a 50-feet dam height.

History: 85-15-110, MCA; IMP, 85-15-210, MCA; NEW, 1988 MAR p. 2489, Eff. 11/24/88.

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