2017-08-16_PERMIT FILE - C2010089A (3)

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suitable material is loaded and hauled around the ends of the pit and is placed on the unsuitable material as a cap, (see Sections 2.05.4(2)(c) Backfilling and Grading and 2.05.4(2)(d) Topsoil Redistribution). The separation of materials (suitable and unsuitable) will help prevent the runoff from more toxic un -oxidized backfill materials from contaminating surface water and place the more toxic percolating ground water (leachate of un -oxidized backfill) below the root zone. It is not anticipated that NHN will transfer ownership or use of any wells completed within NHN permit area. Bore holes, shafts, wells, and auger holes will be cased and/or sealed to prevent possible ground water degradation from the mixing of waters of different quality within the bore holes and acid or toxic surface runoff entering the bore holes. A specific plan for sealing of bore holes, exploration holes, auger holes, wells, and shafts is presented in Section 2.05.6(3)(b)(v), Hydrologic Reclamation Plan. Ground Water Quantity Typical backfilling methods largely involve the use of dozers and trucks (see Section 2.05.4(2)(c), Backfilling and Grading). Replaced spoil materials exhibit greater porosities and hydraulic conductivities because of increased void volumes, regardless of how the spoil material is replaced in the pits. Seepage from the irrigation network has provided an artificial source of recharge to the undisturbed shallow ground water system. Spoil replacement (backfilling) using methods outlined in Section 2.05.4(2)(c), Backfilling and Grading, will allow the infiltration and percolation of storm event water and irrigation water through the backfill. Due to the structural attitude, it is unlikely that the backfill will ever be re - saturated over time. The NHN permit area is located in a semi -arid climate which averages about 12.5 inches of precipitation annually, (see Section 2.04.8 Climatological Information). Evapotranspiration rates in the vicinity are relatively high (see Section 2.04.7, Hydrology Description). Textural analyses performed on potential backfill materials generally indicate that sandy clay loam materials will be replaced in the pits (see Section 2.04.6, Geology Description). Consequently, infiltration rates in reclaimed areas are expected to be slow to moderate which will help water retention in the topsoil and sub -soil. However, the upstream and downstream (above and below the 2nd Park Lateral diversion) irrigation ditches and laterals will continue to recharge the bedrock zones. Again, the irrigation network has provided an artificial source of recharge to the Dakota Formation coal strata bedrock zones in the NHN permit area. Overburden and topsoil handling, reconditioning, and revegetation methods (outlined in Sections 2.05.4(2)(d), Topsoil Redistribution, and 2.05.4(2)(e), Revegetation,) will maximize the potential for establishing reclaimed areas that will exhibit infiltration rates and capacities adequate for insuring at least pre -mining rates and capacities. Timely reseeding and mulching of redistributed topsoil will augment the retention and eventual downward infiltration of soil moisture. Textures of topsoil material will generally range from sandy loam to loam, and topsoil material will exhibit moderate infiltration rates. Deep ripping of re -graded backfill material, followed by topsoil placement, chisel plowing, and disking will improve the infiltration potential of the Section 2.05.6(3) Page 3 April 2016 (PR -01)