Minnesota Administrative Rules
Agency 158 - Natural Resources Department
Chapter 6132 - NONFERROUS METALLIC MINERAL MINING
RECLAMATION STANDARDS
Part 6132.2400 - STORAGE PILE DESIGN
Universal Citation: MN Rules 6132.2400
Current through Register Vol. 49, No. 13, September 23, 2024
Subpart 1. Goals.
Storage piles must be designed and constructed to minimize hydrologic impacts, enhance the survival and propagation of vegetation, be structurally sound, control erosion, promote progressive reclamation, and recognize the conservation of the mineral resources.
Subp. 2. Requirements.
Storage piles must meet the requirements in items A to D.
A. General design: All storage
piles shall be designed and constructed according to the standards in subitems
(1) to (4).
(1) When mine waste is deposited
on areas with unstable foundations such as peat, muskeg, bedded lacustrine
deposits, karst topography, active seismic and flood zones, and areas above or
within a mine, a professional engineer, registered in this state and proficient
in the design, construction, operation, and reclamation of facilities on
unstable foundations, shall examine the foundation and design the storage piles
to ensure stability.
(2) Practices
such as the use of vegetated buffer strips, hay bale dikes, silt fences, or
settling basins shall be used to control erosion.
(3) Rills or gullies shall be observed to
determine dominant runoff flow paths, which shall be stabilized to control
runoff.
(4) Storage piles
containing reactive mine waste must also comply with the requirements of part
6132.2200.
B. Rock
storage piles: The final exterior slopes of lean ore, waste rock, and leached
ore storage piles shall consist of benches and lifts as follows:
(1) no lift shall exceed 40 feet in
height;
(2) no bench shall be less
than 30 feet, measured from the crest of the lower lift to the toe of the next
lift;
(3) the sloped area between
benches shall be no steeper than the angle of repose; and
(4) when vegetation is required under part
6132.2700, subpart 2, item A, subitem (13), the sloped areas between benches
shall be prepared to support vegetation.
C. Surface overburden: Surface overburden
shall be disposed of according to subitems (1) and (2).
(1) When surface overburden is generated, it
shall be placed in layers on the completed tops and benches of lean ore and
waste rock storage piles to enhance reclamation potential.
(2) If no completed tops or benches are
available, or if such sites are not within economic haul distances of surface
stripping activities, surface overburden storage piles shall be created so that
the final exterior slopes shall consist of benches and lifts as follows:
(a) no lift shall exceed 40 feet in
height;
(b) no bench width shall be
less than 30 feet wide, measured from the crest of the lower lift to the toe of
the next lift;
(c) the sloped area
between benches shall be no steeper than 2.5:1; and
(d) runoff water shall either be temporarily
stored on benches or removed by drainage control structures.
D. Mixed storage piles:
Lean ore and waste rock shall not be used to cover surface overburden storage
piles to avoid compliance with sloping and vegetation requirements. This shall
not preclude the abutting of lean ore or waste rock storage piles with surface
overburden storage piles or the placement of lean ore or waste rock lifts on
top of surface overburden pads or lifts.
E. Alternative design: Based on acceptable
research, the commissioner shall approve other measures that satisfy subpart
1.
Statutory Authority: MS s 93.44 to 93.51; 103G.222
Disclaimer: These regulations may not be the most recent version. Minnesota may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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