2021-04-20_REVISION - M1983033 (20)

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Walstrum Spur Amendment, Exhibit G— Water Information 8.1.2 North Clear Creek and Clear Creek Bedrock Exposures April 2021 Bedrock is exposed as an outcrop along North Clear Creek on the east and Clear Creek on the south side of the Spur Amendment. Along North Clear Creek the stratigraphy is incised at an angle to the bedding varying between parallel and perpendicular to strike. This means that along the northern portion of North Clear Creek adjacent to the property, bedrock dips to the north or northeast toward the creek. On the southern end of North Clear Creek, the dip is closer to north, and the outcrops are exposed at closer to the profile of the stratigraphic bedding. Along Clear Creek, the orientation of bedding generally dips away from the creek northward. Neither the east-facing slopes leading down to North Clear Creek, nor the south-facing slopes leading down to Clear Creek appear to contain enough moisture at the surface to result in any form of observed surface discharge. Any moisture sources from the bedrock at the surface result in only enough water to support drought-tolerant grasses and small brush on the southern exposures along Clear Creek in most locations, except where tree roots can access the water present in the Clear Creek alluvium. During the investigation of bedrock exposures along Clear Creek, a historic mine adit that is closed with a grating, was observed on the north side of Highway 6, east of the main entrance to the Existing Quarry. The adit (Location 13 in Figure G-5) was excavated into the exposed bedrock at the base of the cliff. No water was visible either within or discharging from the adit opening indicating saturated conditions are not present in the bedrock. Along with the lack of evidence for seepage at any of the bedrock exposures along Clear Creek, this lack of moisture associated with an excavation directly into the crystalline bedrock further suggests that the bedrock is not a significant pathway for groundwater to discharge laterally to the Clear Creek drainage. 8.1.3 Quarry Pit Highwall Seepage The high walls of the Existing Quarry pit typically show very little evidence of groundwater presence. Small damp patches of rock (5-10 feet long) are visible in the morning, typically corresponding with fractures or bedding surfaces, but these do not flow enough to even reach the floor of the highwall. These observations are particularly noteworthy as they indicate that groundwater only flows through the occasional rock weaknesses, and not in observable quantities through the greater rock mass. Additionally, the limited quantities of observed flow even from these bedding planes and fractures are low enough that their discharge is insufficient to do more than wet the immediate surface of the rock around them before evaporating. The implication is that in the few available conduits for flow, very little groundwater flux occurs, or that groundwater may be compartmentalized and perched within fracture networks that are not significantly interconnected, thereby minimizing lateral flow. 8.2 Nearby Water Wells Tetra Tech performed a database search of the DWR online registry for constructed domestic and commercial water wells. The well search "radius" was one mile from the approximate centroid of the Spur Amendment. The search indicated that 38 constructed wells are registered within this distance of the Spur Amendment. The locations of wells in DWR's registry are approximate. The results of the database search are presented in Appendix G-3 (map and table). In general, the wells are for domestic use and are hundreds of feet deep. Wells in the Floyd Hill neighborhood south of Clear Creek will not be impacted by mining in the Spur Amendment because Clear Creek acts as a groundwater flow divide between the Spur Amendment to the north and Floyd Hill neighborhood to the south. Furthermore, the base of the mine floor will be a minimum of approximately 25 feet above Clear Creek. Likewise, wells in Douglas Mountain neighborhood east of North Clear Creek will also not be impacted by mining in the Spur Amendment because North Clear Creek acts as a groundwater flow divide between the Spur Amendment to the west and the Douglas Mountain neighborhood to the east. The eastern portion of the mine floor will be a minimum of approximately 350 feet above North Clear Creek at the confluence with Clear Creek. Given that Clear Creek acts as a groundwater flow divide, the only wells with the potential to be impacted by the Spur Amendment would be wells located north of Clear Creek or west of North Clear Creek. The only wells that meet these criteria are owned by AFS. The first well, permit# 83805-A, is 30 feet deep, completed in the alluvium, and is just west of the quarry entrance. This well supplies water to the Two Bears Tap and Grill restaurant (owned by AFS), is tributary to Clear Creek, and derives its recharge from waters in the creek. The second well, permit# 03803-F, is owned by AFS, is 120 feet deep, completed in the Precambrian bedrock, and is decreed Tributary to oTETRA TECH P a g e 6 � 7