Current through Register Vol. 48, No. 51, June 17, 2024
Part 6130.2900 - STANDARDS FOR DESIGN AND CONSTRUCTION OF SURFACE OVERBURDEN PORTIONS OF PITWALLS Surface overburden portions of pitwalls shall be designed and constructed to either of the following standards:
A. The final exterior slopes shall consist of benches and lifts as follows: (1) the toe of the surface overburden portion shall be set back at least 20 feet from the crest of the rock portion of the pitwall;(2) lift heights shall range from 40 to 60 feet and shall be selected based on the need to protect public safety; the location of the pitwall in relation to the surrounding land uses; the soil types and their erosion characteristics; the variability of overburden thickness; and the potential uses of the pit following mining;(3) the sloped area between benches shall be no steeper than 2.5:1; and(4) benches shall be sloped into the overburden to control runoff. They shall be large enough to handle runoff water until it can infiltrate into the slope, or a drainage control system shall be constructed to remove water consistent with part 6130.2100, items B and C.B. Based upon acceptable research the commissioner shall approve other measures which satisfy part 6130.2000.Statutory Authority: MS s 93.47