2019-11-20_REVISION - M2004044 (4)

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There will be two methods of mining used within the permit boundary: • Phase 3 will be mined using excavators,transport trucks,and active dewatering during mining. Topsoil will be stripped and stockpiled in locations shown on the Exhibit C Mining Maps. Material will be excavated and transferred to transport vehicles and placed in the designated areas within the East Area, north of Highway 7 to await transfer via conveyor or truck to the processing area at the Wattenberg Mine. • The slurry wall liner for the West and East Areas will likely be installed prior to exposure of ground water on the site. Once the slurry wall is installed the West and East Areas will be dewatered. The deposit will be dry mined using dewatering trenches and pumps within the slurry lined area. Prior to excavation of each mining phase,trenches will be cut along the perimeter of the excavation to begin dewatering the sand and gravel material. The trenches will extend through the overburden and alluvium to bedrock. Pumps will be used to remove the groundwater that drains from the deposit within the lined excavation. If necessary,water from the trenches will be circulated through a settling pond prior to being discharged to adjacent drainage ditches and/or the South Platte River(see Exhibit C Mining Maps). As excavation begins,the mining cell and dewatering trenches on the floor will continue to collect any water entering the lined Areas, keeping the deposit material relatively dry. The collected water will be directed to settling ponds within the Areas or near the final discharge point to South Platte River. It is anticipated that dewatering will be completed within the slurry wall lined mining area within 12 months and dewatering throughout the life of the mine will be limited to precipitation, stormwater runoff that drains into the mining area,and minor amounts of groundwater. Earth Moving Setbacks from the top of slope of each area to the proposed permit boundary or man-made structures not owned by the applicant or by agreement with the structure owner will generally be 30 feet or greater. Specific setbacks from Highway 7 and Tucson Street also account for future expansion of the roadways. The perimeter setbacks from the structures are shown on Exhibit C-Mining Maps. These setbacks were determined in combination with Adams County regulations and the Slope Stability Analysis prepared by Tetra Tech provided herein in the Geotechnical Stability Exhibit. The setbacks reflect the Factors of Safety in the Proposed Slope Stability/Geotechnical Analysis Policy in the DRMS memorandum dated May 16, 2018. Areas to be mined will be prepared by removal of topsoil and overburden. Each preparation area may be as much as 100 feet wide along the anticipated mining face. Usually,only enough area is stripped and prepared to provide the estimated needs for the next 10 to 14 months of mining. Surface topsoil material will be stripped separate from the underlying,deeper subsoil or overburden material. This topsoil layer contains most of the soils organic matter and will be stockpiled separately for use in reclamation. Once the topsoil has been removed,the rest of the overburden will be stripped and stockpiled separate from the topsoil. When the alluvial material is exposed and sufficiently dewatered,the aggregate material will be recovered using equipment typical for sand and gravel mining operations. In the South,West and East Areas,the aggregates will be mined using conventional dry mining methods. Earth moving equipment may include, but is not limited to,dozers, loaders,scrapers,and excavators as mining progresses to a depth of 20 to 50 feet below the surface. The alluvial material is an unconsolidated deposit and,therefore, no blasting is required. The aggregate material from the Areas will be temporarily stockpiled within the various Areas,conveyed to the staging area,or immediately transported off- site for processing. During mining and reclamation activities,watering trucks for dust control will be used as needed. Aggregate Industries Tucson South Resource Permit#M-2004-044112 Permit Amendment Page D-4