2023-10-03_REVISION - M1977344 (32)

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Red Creek Quarry, Groundwater Modeling Analysis 14 DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the beginning of this document. RedCreekQuarry_Modeling_TM_DRAFT_20230911 Table 3. Red Creek Quarry Mine Block Influence on Red Creek Model Results Stream Reach 1 2 3 4 5 6 7 8 9 10 11 Mine Block Rate of Groundwater Entering Stream (ft3/day) 80 to 90 1851 640 64 50 228 135 46 8 0 0 0 90 to 100 1852 640 64 49 228 134 46 9 0 0 0 Section 4: Summary and Conclusions Groundwater flow modeling was conducted to assess potential groundwater flow impacts from the mine blocks. The rate of groundwater entering the mine blocks increased from Mine Block 0-10 through Mine Block 20-30. Following Mine Block 20-30 the MPO pit floor elevations are above the interpolated water table and are therefore dry. The evaluation of the MPO impacts to Red Creek suggested no significant influence to the creek. Section 5: Recommendations for Model Improvements The model results discussed represent a simplistic assessment for the MPO influence on groundwater in RCQ. To improve model predictions, it is recommended to implement additional groundwater monitor wells throughout the site as mining progresses into Mine Block 20-30. This will allow for a more robust set of measured groundwater data for the interpolated water table. Additional groundwater monitor wells located in the central, southern, and eastern portions of the site can be implemented throughout the MPO process to better assess the groundwater at the site. Section 6: Limitations This document was prepared solely for Holcim (US), Inc. in accordance with professional standards at the time the services were performed and in accordance with the contract between the Holcim (US), Inc. and Brown and Caldwell dated July 17, 2023. This document is governed by the specific scope of work author- ized by Holcim (US), Inc.; it is not intended to be relied upon by any other party except for regulatory authori- ties contemplated by the scope of work. We have relied on information or instructions provided by the Holcim (US), Inc. and other parties and, unless otherwise expressly indicated, have made no independent investigation as to the validity, completeness, or accuracy of such information.