2022-11-07_PERMIT FILE - M2022001 (11)

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Table 3 Mininq Groundwater Level Table Slurry Walls In-Place After Slurry Surface Basement Wall Difference(FT Groundwater Depth Elevation Location /n Baseline Construction Rise or Fall) Below Surface Goo le Earth Cell IJK Patnd a House n 47363 47432 6.9 208 4764 161 135,1 Cline House n 4736.8 47451 1 8.3 209 4766 162 1321 Harding House Y 47366 4746.0 93 191 4765 161 1291 Wiedeman House 13434 n 47382 4747.3 91 207 4768 163 121,1 Wiedman House 13218 n 4738.5 47470 8.5 150 4762 1631151 Sharp House 1 1738.4 1745.7 7.3 1 t.4 1760 163,11111 HS Land and Cattle n 47326 4736.1 35 189 4755 1551071 Karbowski Brave House n 4725.5 47245 -1.0 275 4752 145,1081 Schmidt Well NA 4714.4 47096 48 234 4733 1321121 United Well NA 4712.0 47067 -5 3 413 4748 132 1261 Owens Well NA 4714.2 47112 -3 0 34.8 4746 132 1331 Wright House y 47174 47122 -5 2 398 4752 1351321 Schmidt House n 47184 4717.0 -1.4 310 4748 1351351 Smit House y 47188 47184 -0.4 29.6 4748 1351361 Kissler House Y 4729.5 47333 38 217 4755 148 1371 Woolverton House y 47308 47349 41 27.1 4762 150 1361 Shimon House y 47330 47379 49 21.1 4759 154,1361 Kem House y 47338 4739.0 51 211 4760 156 1371 Rainbolt House y 47359 47422 63 22.8 4765 161 1371 Gilcrest Valley HS NA 47370 47407 3.7 53 4746 170,1551 As noted in the table above, groundwater elevation impacts from the installation of the slurry walls will be highly spatially variable. The southeast comer of the Site is expected to see the most amount of mounding, up to 9.4 feet above baseline levels. However,the groundwater table in this area is very deep(from 27 to 30 feet deep),so flooding is not expected to be an issue. Mounding decreases on the upgradient side from east to west,with the Sharp house on the southwest corner of the Site potentially seeing 7.3 feet of mounding. Elevation from Google Earth for the Sharp property is approximately 4760 feet which would put the potential groundwater rise at fourteen (14.4)feet below the surface. Potential shadow effects from the slurry wall are present north of the Site (downgradient). There are three (3)wells on the north side of the Site which will be in the groundwater shadow and changes in depth to groundwater vary from three (2)feet lower to five(5)feet lower for the United well. The shadow effect is likely mitigated by the proximity of the slough to the north of the Site and the infiltration ponds to the northeast of the Site. The modest shadow effect should have limited effect on the productivity local alluvial wells. The Town of Gilcrest is located between the Site and a rise in the bedrock elevation to the east which acts as a no flow boundary. It is anticipated that slurry wall construction will restrict flow to the west of Town causing elevated groundwater levels in Town as noted for"Gilcrest Valley HS"in the table above. 6.2.1 Monarch Mountain Minerals and Aggregates Site Impacts In addition to the Section 20 Gravel Mine,the Monarch Mountain Minerals and Aggregates(MMMA)Monarch DENM Gravel Mine is permitted by the DRMS on the west side of Highway 60. This site is comprised of four(4)slurry wall lined cells and three(3)unlined cells along Highway 60. To simulate the four(4) lined cells, the horizontal hydraulic conductivity in these areas was set to zero(0). To simulate the end stage of the mine it was anticipated that the Groundwater Model Report-Section 20 Gravel Mine Site -8- August 2022