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Section 2.05.4(2)(d) Page 2 December 2021 (RN-02) <br />Overburden and Topsoil Handling Plan <br /> <br />Introduction <br />This section outlines New Horizon North Mine's (NHN) plan for removal, storage and <br />redistribution of topsoil and overburden to meet the requirement of Section 2.05.3(5), 2.05.4(2)(d) <br />and 4.06 for the NHN permit application. The plan addresses those reclamation activities that are <br />conducted during and immediately after backfilling and grading but prior to revegetation. The <br />objectives of the plan are to reconstruct plant growth and aquifer mediums that are consistent with <br />the postmining land uses. The plan also describes the procedural aspects of removal, storage and <br />distribution of topsoil and weathered overburden (Bench 1) and testing of Bench 1. <br /> <br />Overburden and Bench 1 Handling Plan <br />The description of overburden and interburden characteristics and acid and toxic forming materials <br />for NHN Mine are presented in Section 2.04.6. Weathered overburden, also called Bench 1 or free <br />dig material (herein will be referred to as Bench 1), was mined separately from the other <br />unweathered overburden materials (herein will be referred to as overburden). The Bench 1 material <br />was typically comprised of unconsolidated material and was mined in a single bench. It was then <br />hauled and placed on top of the backfilled overburden. All of the Bench 1 was placed immediately <br />below the topsoil in all areas. Bench 1 in its natural state, typical varied from about 20 to 30 feet <br />in thickness within the permit area (see Maps 2.04.6-4 and 2.04.6-5), but was thinner under small <br />drainages where it had been eroded. <br /> <br />During the reclamation process, Bench 1 was used to cap all overburden and the carbonaceous <br />remnants of mining the upper and lower Dakota coal seams. The cap of Bench 1 reduces the <br />potential of leachates and runoff from entering the ground water system or discharging into the <br />surface water system. <br /> <br />Prior to topsoil replacement, Bench 1 was scarified by deep ripping on the contour at least 24 <br />inches on 24 inch centers to reduce excessive compaction, prevent potential slippage zones, reduce <br />erosion, and improve water and air movement and root growth across the Bench 1/overburden <br />interface. <br /> <br />Overburden Spoil Compactibility and Erodibility <br />Determining the compaction potential of the overburden backfill material was important to assess <br />postmining conditions including: hydraulic conductivity, revegetation success, landscape stability <br />and equipment traffic. Unsuitable clay textures were identified in two thin clay beds located in the <br />uppermost overburden in the NHN permit area (see Section 2.04.6, Stratigraphy, Cross Sections <br />A-A’, Map 2.04.6-4). These clay beds occurred about 60 to 65 feet above the top of the lower <br />Dakota seam and only existed in the southern part of the mineable area where the overburden <br />(above the lower Dakota seam) was at least 60 to 90 ft. thick. Map 2.04.6-3, the lower Dakota