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<br /> <br />Portland Limestone Quarries (M-1977-344) Permit Amendment-02 <br />Holcim US Inc, 3500 Highway 120, Florence, CO 81226 Revised pursuant to preliminary adequacy review November 20, 2023 <br />Phone (719) 288-1443 www.holcim.us 74 <br /> <br />Figure 2.4.5-2 Limestone bench mining cross section <br />Daily mining activity will be performed by diesel fueled loaders, a dozer, motor grader, three 100 -ton off- <br />road haul trucks, a 20,000-gallon water truck, and electric backhoes. Once the plant growth material is <br />salvaged and the mine area is leveled, the mine area will be drilled in preparation for blasting at depths <br />based on the geologic stratigraphy of overburden, translime, Fort Hays limestone and Codell sandstone. <br />The drilling patterns are described in the Blasting Plan (Appendix 4.1). The blasted material is segregate <br />as overburden and limestone. Overburden is hauled to the waste dump area and stockpiled for use during <br />final reclamation to rebuild slopes and bring up the elevation of the mine floor or it will be used to construct <br />the perimeter berm. <br />Limestone is processed twice in the RCQ, prior to being conveyed to the BCQ. Electric backhoes will feed <br />one of two electric primary jaw crushers (each rated at 650 tons per hour [tph]) located near the working <br />face. The crushed limestone will be conveyed to the electric secondary cone or impact crusher (rated at <br />1200 tph) located in the vicinity of the shop and office building. The final product conveyed to the cement <br />plant will be approximately 4.5-inch minus. Conveyor belts leaving RCQ will be equipped with a gamma- <br />metrics cross belt analyzer system to provide real-time chemical analysis of the material transported to the <br />plant. <br />2.4.6 Blasting Operations <br />Blasting will occur daily, Monday thru Friday, to yield limestone volumes that provide sufficient quantities <br />of overburden and produce limestone quantities to support plant production. Blasting will conform with <br />Bureau of Alcohol Tobacco, Firearms and Explosives regulations and monitored for seismic control as <br />described in the Blasting Plan (Appendix 4.1). Blasting is performed by a blasting contractor, licensed in <br />CO. At distances of 5,000 feet or greater, the peak particle acceleration will not exceed 1.00 in/sec2. The <br />nearest structure is the Minnequa Canal located within 500 feet of the permit boundary but more than two <br />miles from Sections 24 and 25 in Fremont County. At this distance, ground vibration will not exceed 1.00 <br />in/sec2 thus having no negative impacts to existing structures. <br />2.4.7 Existing Structures <br />Existing structures within the affected area boundary include ranch fences, cattle watering infrastructure <br />and electricity transmission lines. Ranch fences will be removed that are within the affected area. The <br />cattle watering infrastructure, water pipe and troughs, will be dismantled and removed from the affected <br />area. The water supply line to the cattle troughs will be capped at the permit boundary. Holcim will <br />maintain a 25-foot radius setback from electricity transmission lines on the native ground elev ation. In the