17.24.502 CUT-AND-FILL TERRACES
On approval by the department, in order to
conserve soil moisture, ensure stability, and control erosion on final graded
slopes, cut-and-fill terraces may be allowed if the terraces are compatible with
the approved postmining land use and are appropriate substitutes for
construction of lower grades on the reclaimed lands. The terraces must meet the following requirements:
(1) The width of the individual terrace bench may
not exceed 20 feet, unless specifically approved by the department as necessary
for stability, erosion control, or roads included in the approved postmining
land use plan.
(2) The vertical distance between terraces must be
as specified by the department to prevent excessive erosion and to provide
(3) The slope of the terrace outslopes may not
exceed 1v:5h (20%) . Outslopes that
exceed 1v:5h may be approved, if they have a minimum safety factor of more than
1.3 for any condition of load likely to be encountered, provide adequate
control over erosion, and closely resemble the surface configuration of the
land prior to mining. In no case may
highwalls be left as part of terraces.
(4) Culverts and underground rock drains must be
used in the terrace only when approved by the department.
(5) Terraces must be installed in such a way so as
not to prohibit vehicular access or revegetation procedures.
(6) Additional surface manipulation procedures
must be installed as required by the department.
History: 82-4-204, MCA; IMP, 82-4-232, MCA; NEW, 1980 MAR p. 725, Eff. 4/1/80; AMD, 1989 MAR p. 30, Eff. 1/13/89; TRANS, from DSL, 1996 MAR p. 3042.