2024-02-01_REVISION - M1973021 (2)

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Ninth Technical Revision (TR09) to Permit M-1973-021, Holcim- WCR, Inc. Morrison Quarry January 2024 | 1 1 Introduction 1.1 Purpose and Objectives The purpose of this document is to support the request to the Colorado Division of Reclamation Mining and Safety (DRMS) for a Technical Revision (TR) to the 112c Reclamation Permit Operations for Morrison Quarry (File number M-1973-021). The objective of this document is to provide a narrative and updated Exhibits that explain the requested revisions to the approved Phase III Mining and Reclamation Plans based on anticipated exposure of groundwater in the South Quarry. Revised Exhibits include the following: Exhibit D – Mining Plan Exhibit E – Reclamation Plan Exhibit F – Reclamation Plan Map Exhibit G – Water Information Exhibit L – Reclamation Costs Rule 6.5 – Geotechnical Stability Exhibit Specifically, Holcim requests that the Phase III South Quarry mining plan and reclamation plans, below elevation (El.) 6,600, be modified to focus mining operations in an area referred to as the Satellite South Pit. The Satellite South Pit mining will proceed in accordance with the mining plan for the South Quarry approved in AM07 for benches below El. 6,600. Based on groundwater level monitoring in and around the South Quarry, groundwater is anticipated to be encountered. This TR also discusses how groundwater will be managed in the South Quarry once encountered. Other revisions to the approved reclamation plan include the following: · Updates to the drainage plan for the South Quarry specifically drainage for the reclaimed West Wall of the South Quarry; · Updates to the reclamation plan to remove the South Quarry horizontal drain; and · Modification to groundwater monitoring requirements in the South Quarry based on ongoing efforts to complete a Substitute Water Supply Plan (SWSP) and well permit for the South Quarry. 1.2 Background Morrison Quarry is a hard rock aggregate mine located west of Colorado Highway 8 and approximately 0.5 miles north of U.S. Highway 285 in Morrison, Colorado. The mine site is located west of the Dakota hogback along the Colorado Front Range west of Denver. Morrison Quarry currently consists of four mining cells that are either active or in reclamation stages: the North Quarry, the Central Quarry, the South Quarry, and the West Quarry. Active mining is limited to the South Quarry and West Quarry.