2024-11-04_PERMIT FILE - M2024056 (6)

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Evans Mining Resource Groundwater Monitoring Plan October 2024 Page 2 groundwater quality).The final data sets used to document the pre-operational baseline conditions will be submitted in the Baseline Data Summary Report to DRMS. 2.1 MONITORING WELL NETWORK Seven(7)monitoring wells(MW-1 through MW-7)have been installed in accordance with DWR standards within the unconsolidated alluvium at the Site to characterize baseline groundwater conditions.Three(3)of the monitoring wells(MW-1,MW-2,and MW-3)are located hydraulically up-gradient along the western and southern boundaries of the Site. Three (3) monitoring wells (MW-4, MW-5, and MW-6) are located hydraulically down-gradient along the northern and eastern boundaries of the Site. The seventh monitoring well (MW-7), located along the eastern boundary, was installed as an observation well to monitor groundwater levels. The location of the monitoring wells is shown in Figure 2. Borings were installed utilizing 4-1/4" ID hollow stem auger(HSA)drilling method from ground surface to the top of underlying bedrock.Monitoring wells are constructed of two(2)-inch diameter Schedule 40 PVC with factory slotted 0.010" slot size for the screened portions. The filter packs consist of 10/20 silica sand and extend approximately two(2)-feet above the top of the well screen. A bentonite seal (chips) was installed from the top of the filter pack to ground surface. At the surface, a two (2)-foot x two (2)-foot concrete pad was installed around each well along with a four (4)-inch square steel well cover with hinged locking cap to protect the above ground riser. Copies of the monitoring well construction logs are provided in Appendix A. 2.2 BASELINE GROUNDWATER QUANTITY Groundwater elevations collected from monitoring wells at the Site are presented in Table 1. The general direction of groundwater flow across the Site is to the northeast towards the South Platte River as shown in the potentiometric map presented in Figure 3. A graph depicting the fluctuation in groundwater elevations during the baseline monitoring period to-date is presented in Figure 4. 2.3 BASELINE GROUNDWATER QUALITY 2.3.1 Groundwater Quality Benchmarks The objective of the baseline groundwater monitoring is to document the pre-operational groundwater quality levels for applicable Water Quality Control Commission(WQCC)Regulation 41 Interim Narrative Standards(INS)Tables 1 —4(5 CCR 1002-41)parameters(Table 2)prior to mining. This data will be used to establish the site-specific groundwater quality benchmarks for the Site once mining operations begin. Per Rule 3.1.7(2)(c)(ii),the lowest WQCC Regulation 41 INS Tables 1 — 4 standard for analytes are utilized as the default numeric protection value benchmarks, except for analytes where baseline groundwater concentrations exceed these values. For exceeding analytes, the highest concentration reported during the baseline groundwater characterization period will be used as a site-specific groundwater quality benchmark. The site- specific groundwater quality benchmarks will be used for comparison against future groundwater sampling event results to demonstrate protection of existing and reasonably potential future uses