Minnesota Administrative Rules

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

Published Electronically:

June 11, 2008