2023-10-03_REVISION - M1977344 (32)

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Mr. Kevin Rein Office of the State Engineer Page 2 Based on these findings and the fact that mining will not begin until approximately 2027, no replace- ment of depletions associated with mining will be necessary during 2025. Further analysis and quanti- fication of depletions associated with the interception of groundwater from future planned mining will accompany the preliminary engineering for the amendment to Case No. 16CW3102. Water Use at RCQ Mine Site Water will be needed at the RCQ Mine Site for both dust suppression and sanitary purposes. Holcim has anticipated the need for two groundwater wells to provide the supply for these uses. Well siting will occur in 2024 and applications for well permits will be submitted to the Division of Water Resources once the well locations have been selected. It is anticipated that these wells will be installed in 2025. Dust Suppression. Water needed for dust suppression is dependent on the amount of product mined and the mining operations. Holcim will be utilizing a more efficient mining process that reduces equip- ment impacts and dust. Dust suppression systems will also be installed on the conveyor system that transports mined product to the cement plant. Dust suppression projections for the Bear Creek quarry estimated a maximum use of 70 acre-feet per year. However, the RCQ would likely only need 60% of that amount, or approximately 40 acre-feet per year once mining begins. Dust suppression needs during construction are difficult to estimate. Therefore, water pumped from the wells for this use will be measured and reported, but are not expected to exceed 20 acre-feet per year. Dust suppression uses will be considered 100% consumptive. Sanitary Needs. Typical water use at the Bear Creek Quarry and Cement Plant for domestic needs (bathrooms, kitchen) are on the order of 30 acre-feet per year. The RCQ site will only have approxi- mately 25 staff, and so these uses are estimated to be only 1 to 2 acre-feet per year (based on typical per capita usage). These uses are considered to be 10% consumptive, with the remaining water return- ing to the groundwater system through a septic/leach field system. Total Water Use. Assuming that well permits are obtained this fall and two wells are installed by Janu- ary 1st, Table 1 presents the monthly projected water pumped and used for dust suppression and sani- tary needs in 2025 at the RCQ site. Table 1. Projected Water Use from Groundwater Wells at RCQ Dust Suppression Use/Consumed Sanitary Use Sanitary Consumed Total Water Consumed from Wells Jan 1.75 0.17 0.02 1.77 Feb 1.75 0.17 0.02 1.77 Mar 2.25 0.17 0.02 2.27 Apr 2.75 0.17 0.02 2.77 May 3.00 0.17 0.02 3.02 Jun 4.25 0.17 0.02 4.27 Jul 4.25 0.17 0.02 4.27 Aug 4.25 0.17 0.02 4.27 Sep 3.50 0.17 0.02 3.52 Oct 3.25 0.17 0.02 3.27 Nov 2.75 0.17 0.02 2.77