17.24.635 GENERAL REQUIREMENTS FOR TEMPORARY AND PERMANENT DIVERSION OF OVERLAND FLOW, THROUGH FLOW, SHALLOW GROUND WATER FLOW, EPHEMERAL DRAINAGEWAYS, AND INTERMITTENT AND PERENNIAL STREAMS
(1) The department may require or approve a diversion of flow whenever:
(a) the purpose is to divert water away from disturbed areas, to minimize erosion, to reduce the volume of water requiring treatment or to prevent or remove water from contact with acid- or toxic-forming materials; and
(b) the department finds that the diversion will not adversely affect the water quantity and quality and related environmental resources of the stream. (See also ARM 17.24.633, 17.24.634, 17.24.651, and 17.24.751.)
(2) A diversion that increases the potential for landslides or allows entry of diverted water into underground mines must not be created.
(3) Diversions must not be constructed to pass large flow events into an adjacent drainage channel that would result in excessive erosion in the natural channel. Water in excess of the design event must be conveyed in a stable manner to an appropriate treatment facility to meet effluent limitations before passing off the permit area.
(4) (a) Diversions must be designed, constructed, stabilized, and maintained to prevent additional contributions of suspended solids to streamflow, to runoff outside the permit area, to prevent material damage to surface and ground water outside the permit area, and to assure the safety of the public to the extent possible, using the BTCA.
(b) Materials used to construct diversions must be approved as acceptable by the department prior to their use.
(5) The design and construction of all stream channel diversions and any related structures must be certified by a qualified licensed professional engineer as meeting the performance standards and any design criteria set by the department.