2022-05-10_GENERAL DOCUMENTS - M1993041

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Dowe Flats Quarry Soils and Geology Report 4 to 7 inches thick, somewhat thinner than described in Moreland and Moreland (1975) where the upper horizon was described as 8 inches thick. Underlying was a layer of pale brown calcareous loam about 4 inches thick. Depth to parent material varied from 11 to 13 inches. These soils were present much as mapped, except where they.extended into areas mapped as Gaynor (see Section 2.1.1.3). The thickness of the surface material likely to be salvaged for reclamation varied from 4 to 10 inches. 2.1.1.3 Gaynor Soils The Gaynor silty clay loam soils covered approximately 13% of the property based on the NRCS mapping (Moreland and Moreland 2008). They are moderately deep soils derived from loamy alluvial and wind-blown materials. They are found in areas of wind deposits which tend to be difficult to accurately predict. Much of the area mapped as Gaynor was described as either LaPorte or Manvel series in the field sampling. The surface A-horizon layer was a grayish brown silty clay loam about 6 inches thick. Below this was a brown silty clay loam about 4 inches thick. The underlying layer of silty clay loam extended approximately 20 inches deeper. The surface material likely to be salvaged for reclamation averaged 8 inches in thickness. 2.1.2 Other Soils of the Permit Area Several other soil units were mapped within the Dowe Flats property and together represented the remaining 6% of the area. These soil units were either not disturbed or experiences very minor disturbance. These soils included Calkins sandy loam, Nunn clay loam, Nunn sandy clay loam, Playas, and Valmont cobbly clay loam. Calkins sandy loam soils were mapped as less than one acre on the far northeast edge of the property outside the mining area. These soils are coarse loamy, mixed, mesic Cumulic Haplaquolls. Deep and somewhat poorly drained, there were formed from loamy alluvium on low terraces and bottomlands. Nunn sandy clay loam and Nunn clay loam soils were mapped along the west edge of the property west of the HiCal ridge outside the mining area. These soils are fine montmorillonitic, mesic Aridic Argiustolls, are deep and well-drained, and are formed on terraces and valley side slopes in loamy alluvium. The Nunn sandy clay loam and Nunn clay loam were mapped separately. Playas were not included in the original soil description for Dowe Flats but were mapped in the 2008 survey in a single area where the 3`d Ridge Pit now resides. Playas are closed depressions that intermittently hold water from runoff and storm events. The surface soils in playas tend to be of finer texture than the surrounding area and are often more saline and alkaline. Because this area was not described differently from the surrounding area on the pre-mining maps, the surface soils were likely salvaged and stockpiled along with the surrounding topsoil. Valmont cobbly clay loam soils were mapped by slope class (1-5% and 5-25%) on the northwest edge of the property west of the HiCal ridge outside the mining area. These soils are clayey over loamy-skeletal, montmorillonitic, mesic Aridic Argiustolls. They are deep and well- drained, and are formed on old, high terraces in cobbly and gravelly loamy alluvium. 2.2 Soil Salvage and Suitability Prior to mining, soil samples were submitted to the Colorado State University Soils Laboratory for verification of reclamation suitability. Based on those soil results and recommendations from 2 May 2, 2022