Overburden Replacement

· When removing the overburden, many companies place the overburden next to the pit. As the mining of Bentonite occurs, the overburden is filled in behind the mining operation as it moves along the Bentonite seam.
· Through years of sampling and testing, some specialists have found the overburden quality decreases with depth, and have developed a tier, or stair-step backfill system, that is made of three areas of overburden:
1. Low quality overburden (which usually consists of hard shale and cleanings)
2. Middle overburden
3. Third lift (fine shale found below the soils)
· The replacement begins with the low quality overburden, which is placed on the bottom of the pit. The middle overburden is then put on top of the low quality overburden, which is followed by the third lift material. This brings the surface to grade.

· Topsoil Replacement

· Pre-mine soil surveys document the quality and quantity of soil resource. Then, the topsoil and subsoil are handled separately and hauled directly to backfills whenever possible. If the soils cannot be used for backfills immediately, they are stockpiled for later use.