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Aggregate Industries, Morrison Quarry <br /> Amendment No.7 to Permit M-1973-021 FYZ <br /> Morrison,CO <br /> Exhibit D — Mining Plan <br /> Rationale for Amended Mining Plan <br /> Since initiating Mining Plan Phase III (opening the South Quarry), local rock observations and <br /> stability challenges have resulted in more conservative benching and reduced production. <br /> Additionally, groundwater monitoring wells have identified water levels that require expedited <br /> well permitting, water plan modifications, and groundwater water management planning. A <br /> mining plan modification is required to meet business needs while conducting additional studies <br /> to better understand stability issues and water management needs. <br /> The substantial changes proposed by this amendment are: <br /> • Revisions to the Phase III bottom of mining elevation to reflect average groundwater <br /> monitoring elevations in the South Quarry monitoring wells; <br /> • Exceptions to bench standards based on geotechnical evaluations and operational <br /> observations in the South Quarry; <br /> • Inclusion of water management requirements based on current water level measurements in <br /> the South Quarry monitoring wells; and <br /> • Establishing a requirement to modify this permit before Phase IV mining operations can <br /> begin. <br /> Other changes to the mining plan include the redesignation of the ridge west of the Central <br /> Quarry as the West Quarry, inclusion of the West Quarry haul road in the Mining Plan, and <br /> inclusion of the Unnamed Drainage 1 and 2 (UD#1 and UD#2) draft final design package to <br /> satisfy outstanding permit stipulation #10 (refer to Additional Information for stipulation details). <br /> General Mining Approach <br /> Amendment No. 05 (AM05) identified a four-phase mining approach focused on: 1) developing <br /> the quarry in a manner that will disturb only limited areas each time; 2) facilitating reclamation of <br /> mined slopes in inactive areas in a timely manner; and 3) accommodating mine operations <br /> considerations. Phases I and II were established to develop the Central Quarry and North <br /> Quarry; mining operations in these areas are complete and reclamation activities are ongoing. <br /> Phases III and IV focus on development of the South Quarry, utilizing highwalls and benches <br /> primarily on the western (east-facing) mountain slopes of the South Quarry; these activities are <br /> ongoing. <br /> September 2021 1 16 <br />