2024-01-31_REVISION - M1977344 (18)

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Portland Limestone Quarries (M-1977-344) Permit Amendment-02 Holcim US Inc, 3500 Highway 120, Florence, CO 81226 Revised pursuant to preliminary adequacy review November 20, 2023 Phone (719) 288-1443 www.holcim.us 71 In Years 0 to 10, initial mine development will occur within 18 acres to provide a cleared area for construction of the shop and office building, utilities, MTAC and secondary crusher. It is anticipated to take up to two years to complete the infrastructure development. Upon completion of development, mining will continue in Sections 24 and 25 for the remaining eight years on approximately 216 acres. Codell sandstone will be mined in this area to a depth of 15 feet, crushed and transported to the plant. In Years 10 to 20, mining will continue in the northwest corner of Section 24, depleting the limestone in this area by Year 20. Mining will also continue south into Section 25 during Years 10 to 20. Approximately 269 acres will be mined in Sections 24 and 25 during this period, including continued extraction of Codell sandstone in Section 24. At the end of year 20, contemporaneous reclamation will begin in Section 24. As mining progresses into the east portion of Section 25, overburden may be hauled to Section 24 for rebuilding slopes to 3H:1V. Reclamation will continue similarly as mining progresses into the Pueblo County sections. In Years 20 to 30 mining will continue in Section 25 moving east across the resource. This period will experience the highest strip ratio as the thickness of the overburden will be the thickest throughout the deposit. Extraction from the top 15 feet of the Codell sandstone will continue in Section 25 once sufficient acres of limestone have been removed to expose the top of the Codell sandstone. Phase reclamation will continue in Section 24 and the area used for sandstone extraction in Section 24 will be backfilled and reclaimed. Approximately 240 acres will be affected during this period. In Years 30 to 40 mining will continue in an easterly direction. Extraction from the top 15 feet of the Codell sandstone will continue in Section 25. It is estimated that the limestone in Section 25 will be depleted during the last half of this 10-year period and mining will continue moving eastward into Sections 19 and 30 in Pueblo County. Approximate affected acreage during this 10-year period is 478 acres. During Years 40 to 100 (approximate life of mine) mining progression is speculative at best. Mining will continue eastward through the deposit in similar manner as described above including contemporaneous reclamation in mined out areas.