17.24.605 HYDROLOGIC IMPACT OF ROADS AND RAILROAD LOOPS
(1) Access and haul roads and railroad loops and associated bridges, culverts, ditches, and road rights-of-way must be constructed, maintained, and reclaimed to prevent additional contributions of suspended solids to streamflow, diversions, or to runoff outside the permit area to the extent possible, using the BTCA.
(2) Drainage ditches must be placed at the toe of all cut slopes formed by the construction of roads. Drainage structures must be constructed to cross a stream channel and must not affect the flow or sediment load of the stream unless otherwise approved by the department in writing for a site-specific situation.
(3) Railroad loops and all roads except ramp roads must be adequately drained using structures such as, but not limited to, ditches, water barriers, cross-drains, ditch-relief drainages, culverts, and bridges.
(4) For railroad loops and for roads that are to be maintained for more than six months and for all roads used to haul coal or spoil (excluding ramp roads) or to be retained for the postmining land use, water-control structures must be designed with a discharge capacity capable of safely passing the peak runoff from a 10-year, 24-hour precipitation event or greater event as specified by the department.
(5) Bridges with a span of 30 feet or less must be designed to safely pass a 25-year, 24-hour precipitation event. All other bridges must be designed to safely pass the 100-year, 24-hour precipitation event or greater event as specified by the department.
(6) Drainage pipes and culverts must be constructed to avoid plugging or collapse and erosion at inlets and outlets. Culverts must be designed, constructed, and maintained to sustain the vertical soil pressure, the passive resistance of the foundation, and the weight of vehicles to be used.
(7) Natural channel drainageways must not be altered or relocated for road or railroad loop construction or reconstruction without the prior approval of the department in accordance with ARM 17.24.635 through 17.24.637. The department may approve alterations and relocations only if:
(a) the natural channel drainage is not blocked;
(b) no significant damage occurs to the hydrologic balance; and
(c) there is not adverse impact on adjoining landowners.
(8) Drainage structures are required for stream channel crossings. Drainage structures must not affect the normal flow or gradient of the stream or adversely affect fish migration and aquatic habitat or related environmental values. Riprap may be used for roads where an ephemeral channel is too shallow for placement of a culvert.
(9) Vegetation must not be cleared for more than the width necessary for road, railroad loop, and associated ditch construction, to serve traffic needs, and for utilities.
History: 82-4-204, MCA; IMP, 82-4-231, 82-4-232, MCA; NEW, 1980 MAR p. 725, Eff. 4/1/80; AMD, 1989 MAR p. 30, Eff. 1/13/89; AMD, 1994 MAR p. 2957, Eff. 11/11/94; TRANS, from DSL, 1996 MAR p. 2852; AMD, 1999 MAR p. 811, Eff. 4/23/99; AMD, 2004 MAR p. 2548, Eff. 10/22/04.