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 | 4 Groundwater Management Groundwater measurements in and around the proposed Satellite South Pit identify groundwater levels between El. 6,588 and El, 6600. These water levels and locations are presented in Table 1. Table 1: South Quarry Water Level Measurements Well ID/Boring # Location 2022 Water Level (Elevation (ft)) MW-2019-02 South of the South Quarry 6,588 HDR-001P Current South Quarry pit floor (El, 6,600) 6,595 HDR-002 Current South Quarry pit floor (El, 6,600) 6,588 HDR-003 Current South Quarry pit floor (El, 6,600) 6,592 HDR-004 Current South Quarry pit floor (El, 6,600) 6,600 These water levels indicate that Holcim will need to manage groundwater as the Satellite South Pit is advanced. To evaluate potential groundwater in-flows, HDR conducted a hydrogeologic analysis, using acoustic televiewer and flowmeter tools, to evaluate fracture networks and flow rates at four observation holes within the South Satellite Pit footprint. Flows in these borings were low, ranging from 0.01 to 0.19 gallons per minute under ambient flow conditions. Using this flow data and the planned Satellite South Pit geometry, it is estimated that approximately 5 gallons per minute of water would potentially require management during mining operations. To manage this anticipated groundwater, as mining proceeds in the South Quarry, mining operations will proceed from east to west, creating a low point on the east side of the pit, south of the spur road. A sump will be maintained in the pit where accumulated groundwater will be pumped and either (1) discharged to Outfall 006 (directly east of the proposed sump location); (2) used directly on site; or (3) stored on site and evaporated. Concurrent with this TR, Holcim is preparing a water court application (including an application for a plan for augmentation), substitute water supply plan (SWSP), and well permit application to allow for the interception of groundwater and to replace depletions from the interception, exposure, storage, and use of groundwater. The augmentation plan will use water rights owned by Holcim and jointly owned by Holcim and the Town of Morrison, as well as other leased water rights. Holcim is still in the process of finalizing technical details for the applications and has not yet identified a specific filing date; however, Holcim anticipates the augmentation plan application will be filed in 2024, with the SWSP and well permit applications to be submitted contemporaneously. In any event, Holcim will not mine into and deplete groundwater without a pending augmentation plan and associated SWSP and well permit submissions. Prior to submission of the SWSP and well permit applications, if groundwater is exposed during mining, operations will cease in that area and the portion of the excavation causing exposure of groundwater will be backfilled. It is anticipated that Holcim will not obtain a permanent augmentation plan for at least one to two years after the water court application is filed. Surface Water and Stormwater Management