2022-04-29_PERMIT FILE - C2010089 (12)

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Section 2.04.9 Page 29 December 2021 (RN-02) As directed by the DRMS in consultation meetings in Grand Junction, the physical and chemical properties of each soil type were subject to the topsoil suitability criteria recommended by the DRMS, that being the Wyoming Department of Environmental Quality Topsoil Suitability Guideline. With respect to coarse fragment content, which was found to be the most limiting criteria for these soils the DRMS directed that for one lift topsoil salvage operations, such as are proposed herein, coarse fragment content could not exceed 20 percent. The locations of all soils test pits were delineated using a Trimble Model Geo XH Global Positioning System, which typically as a real time accuracy of less than on meter and inserted into the detailed two foot contour interval map generated for this project. In addition to the formal soil backhoe test pits, a total of 174 soil pits, were dug with a shovel in connection with the formal wetland delineation which was conducted on this site to satisfy the wetland delineation requirements of the U.S. Army Corps of Engineers (COE). The locations of these wetland soil test pits are shown on Map 2.04.9-2, New Horizon North Mine-Soils. According to the requirements of the COE, as found in the 1987 Corps of Engineers Wetlands Delineation Manual and the recent supplement entitled Regional Supplement to the Corps of Engineers Wetlands Delineation Manual: Arid West Region issued in 2005, at each wetland sample plot a soil pit typically, 18 to 20 inches in depth was dug and various soils parameters recorded. Typically at a depth immediately below the bottom of the A horizon or at a depth of 10 inches the soils were analyzed for field texture, matrix color, the presence of redox features, the presence of hydric soils indicators as well as the type and depth of restrictive layer if determined at each wetland sample plot locations. This information was recorded on the WETLAND DETERMINATION FORM - Arid West Region form issued by the COE and is included in the 404 Permit application submitted to the COE. In this soils investigation a total of 35 of the wetland sample plots resulted in a measured depth of the restrictive layer or the depth of potentially salvageable topsoil. This pertinent information is presented on Map 2.04.9-2, New Horizon North Mine-Soils Map. Due to the level of intensity used in the NHN soil survey effort, it was possible to further refine the NRCS mapping shown on Map 2.04.9-1, New Horizon North Mine-NRCS Soils Map. The refinements made to the NRCS soils mapping are found on Map 2.04.9-2, New Horizon North Mine-Soils Map. These changes included the modification of the NRCS soils mapping unit 10, Aquolls, 0 to 3 percent slopes. A careful analysis of the original NRCS mapping reveals several areas along the north side of Meehan Draw where this mapping unit was mapped as being present on areas containing upwards of 60 percent slopes. This error is probably due to the fact that the NRCS field personnel did not have the benefit of having detailed two foot contour interval topographic mapping when they mapped the soil boundaries on these areas. Another error in the NRCS soils mapping had to do with their delineation of soils mapping unit 71, Nyswonger silty clay loam, 1 to 4 percent slopes being presence on this site. This soils mapping