2021-02-03_REVISION - M2020008 (4)

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Rifle Gravel Pit#1 January 2021 (Amendment to File No. M-2020-008) 5.0 Exhibit D Mining Plan 5.1 Project Location and Information The proposed Rifle Gravel Pit #1 site is located on a 58.7-acre parcel along CR 346 (1-70 North Frontage Road) which begins at Mamm Creek Road on the west and ends in a cul-de- sac approximately 2.1 miles east of Mamm Creek Road. Approximately 0.5 miles east of Mamm Creek Road, CR 346 turns from a paved 2-lane roadway to a gravel two-lane roadway and remains gravel to the cul-de-sac at its east terminus. The proposed access driveway to the site is located 1.1 miles east of Mamm Creek Road on the north side of CR 346 (1-70 North Frontage Road), see Figures 1 and 2. Gravel and sand will be the primary and secondary commodities that will be mined/extracted. These materials will support various projects. 5.2 Mine Facilities and Operation The site has approximately 3 million tons of minable material that will be extracted in 4 phases over 5 to 7 years. The phases are as follows: • Site development and grading (Phase 1) • Mining preparation (Phase 2) • Mining extraction (Phase 3 — in 5 Stages) • Reclamation (Phase 4) 5.2.1 Site Development and Grading (Phase 1) 5.2.1.1 Topsoil and Overburden Handling This phase of the project will include minor site grading, vegetation removal and construction of the site access/driveway. A clean water diversion channel will be constructed to intercept site run-on water and reroute it around the construction activities to its historical point of discharge from the property where it will be conveyed to the Colorado River along the existing flowpath. SCI will assess the need to construct a sedimentation basin in the northwestern portion of the property if there is a need to provide additional sedimentation for purposes of complying with the CDPHE-WQCD's Construction Stormwater Permit and associated Stormwater Management Plan (SWMP) requirements. The mine will use conventional earth moving equipment to stockpile topsoil and gravel including, but not limited to a bulldozer, track-hoe, and a 35-ton haul truck. The existing topsoil will be stripped and used for the required berms along the perimeter of the site. These berms will be place inside of a 25-foot set back area from the property line. These berms will be roughly 5-feet in height and 23-feet wide at the bottom and will help control noise produced during operation. See Figure 9, Exhibit D for additional information regarding the topsoil and overburden handling. Note overburden materials across the site vary. The boring holes indicate the overburden depth can vary from 1 foot to 2.5 feet. Attachment C includes the typical cross-sections at the boring holes. 15