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Wattenberg Lakes Amendment, Exhibit D—Mining Plan May 2023 <br /> overburden, process fines, and other inert materials from on-site. If materials from off-site are used, Holcim will <br /> provide the Division with the appropriate notices and affidavit in accordance with Rule 3.1.5(9). <br /> During mining and prior to reclamation, the mine walls will be nearly vertical at a 0.5H:1 V slope. The aggregate <br /> material will be temporarily stockpiled or placed directly onto a conveyor system for transport. The conveyor <br /> system will transport the material to be processed at an existing DBMS permitted mining site (Permit Number M- <br /> 89-120) immediately east of the property (Holcim's Platte Valley Plant). The conveyor will cross the South Platte <br /> River within the permit boundary before entering the adjacent mining site as illustrated on the Pre-Mining/Mining <br /> Plan Map (Exhibit C). Alternatively, if needed, a limited amount of material may be processed on-site with portable <br /> and temporary screening, crushing, and/or washing equipment. <br /> Once backfilling and grading has been completed in an area, the top of the slope and the side slopes above the <br /> anticipated reservoir water level will be seeded as soon as practicable (in first available seeding season). <br /> Prior to and during removal of the materials in Area 1 and Area 2, a dewatering system will be operated using the <br /> current pump system that is on site. If additional capacity is needed, the pump system will be upgraded. <br /> Dewatering trenches will be excavated around the perimeter of each pond and pumps will be used to remove the <br /> water that drains from the deposit and surrounding alluvium into the trench. The water removed during dewatering <br /> Will be used for dust control at the site or piped to the nearby unlined Stillwater Ski Lake (owned by Holcim) or to <br /> permitted outfall 8 at the South Platte River. Stormwater that falls within the mine areas will drain internally and <br /> will also be removed through dewatering operations. There will not be uncontrolled releases of surface water and <br /> sediment from mining areas. <br /> Water associated with the site will be used for dust control operations during use of the roads and for stockpiles <br /> and berms. The water used to limit dust emissions will be applied using a water truck with capacity of 2,500 or <br /> 4,000 gallons. As noted above, water for dust control will come from the dewatering process. <br /> No explosives will be used to mine the site. <br /> 3.0 STOCKPILES <br /> Growth medium and overburden in the Area 1 and Area 2 mining area will be stripped with scrapers or a dozer <br /> and placed separately in temporary stockpiles to the north and west of the mining area. The growth medium will <br /> be segregated and stored separately (see Exhibit C-1 map) to the north of Pond 1 and the overburden material <br /> will be temporarily stored to the north and west of the mining area, as required by Rule 3.1.9(1). The stockpiles <br /> will have an average height of 8 feet tall; they will have maximum 3H:1 V side slopes. The overburden stockpiles <br /> will be used for backfilling and reclamation where needed on the site. No excess overburden is anticipated for this <br /> site. <br /> The growth medium stockpile will be protected from wind and water erosion by vegetative cover(see the Seed <br /> Mix for Upland Areas found in Exhibit E). Also, overburden stockpiles reserved for reclamation will be vegetated <br /> and stabilized in accordance with Rule 3.1.9(1). The stockpiles will be broadcast seeded and incorporated into the <br /> weed control program. Weed control consists of chemical treatments as needed in the applicable fall and spring <br /> seasons. <br /> 4.0 COMMODITIES TO BE MINED <br /> The primary commodity to be mined will be aggregate. Holcim will supply local, county, and state governments, <br /> as well as private industry with aggregate from this facility. <br /> 5.0 OFFSETS <br /> The mining area will be subject to setbacks to prevent disturbance of road and utility rights-of-way and <br /> undisturbed wetland areas. Holcim will maintain a 200-foot minimum setback from the South Platte River. In the <br /> Pond 1 area, the limit of mining will be at least 40 feet from the proposed permit boundary or county roads (see <br /> the Pre-Mining/Mining Plan Map, Exhibit C). In all other areas, a minimum 25-foot setback will be maintained from <br /> OTETRA TECH Page 3 1 4 <br />