2021-04-20_REVISION - M1983033 (20)

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Walstrum Spur Amendment, Exhibit G— Water Information April 2021 Clear Creek for 15 gpm. The mining in the Spur Amendment will not impact flows in Clear Creek; consequently, these wells will not be impacted by mining. 8.3 Existing Information At many sites, the presence of groundwater in steep terrain is commonly observed in the form of seeps on slopes or in incised drainages. Therefore, as part of the hydrogeologic reconnaissance, evidence for near-surface and bedrock groundwater was investigated at bedrock outcrops, along topographic lows associated with drainages and on the faces of the Existing Quarry pit highwall. The slope of the land surface is shown in Figure G-4. Slopes around the quarry property are typically greater than 10 percent grade. Since steeper slopes generally lead to more rapid surface water response to precipitation, there is less time for water to infiltrate before exiting as surface-water runoff for a given area. The observed distribution of slopes, therefore, generally reinforces the expectation for a low proportion of precipitation contribution to groundwater. As verified by core drilling and field mapping for this application, joints and fractures observed at the site commonly exhibit two joint-set orientations. The dominant set, observable throughout the mine property, is expressed in a near-vertical northwest-southeast orientation (330/80 NE), while a secondary set is typically oriented 315/80 NE. An additionally mapped tertiary set trends east-northeast to southwest. Voids associated with fractures and joint sets are anticipated to represent the only significant form of porosity. The primary orientation of the fracture network suggests that water flow within it would most likely be expected to discharge along the east or south-facing aspects of the Clear Creek Canyon. The width of fractures typically become smaller with greater depth in bedrock due to the increased pressures associated with the overlying rock mass. This likely leads to a reduction in the extent of interconnected fractures with depth. The fracture network may, therefore, act as compartmentalized, low-volume reservoirs in the bedrock below a certain depth, although no seeps or springs were observed in the Spur Amendment or Clear Creek Canyon. This hypothesis indicates that the deeper localized fractures would likely only drain if intercepted during mining and are not capable of sustained flow. Field reconnaissance for this permit application did not indicate springs or seeps associated with these faults and an absence of springs and seeps on the canyon walls of Clear Creek. The lack of spring and/or seeps in the canyon walls is consistent with observations of only a few damp spots or seeps in the highwall of the Existing Quarry. Consequently, it is concluded that the rock mass is generally very low in permeability. 9.0 CITATIONS/REFERENCES Schwochow, S.D., 1989. "Review of Geology and Critical Geologic Factors in Operation of the Walstrum Quarry — Clear Creek, CO" USGS; Sheridan, Douglas M, and Marsh, Sherman, P. 1976. "Geologic Map of the Squaw Pass Quadrangle, Clear Creek, Jefferson and Gilpin Counties, Colorado" U.S. Geological Survey. USGS; Taylor, Richard B. 1975. "Geologic Map of the Black Hawk Quadrangle, Gilpin, Jefferson, and Clear Creek Counties, Colorado" U.S. Geological Survey. OTETRA TECH P a 9 e 7 ��