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

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Evans Mining Resource Groundwater Monitoring Plan October 2024 Page 5 4.2 GROUNDWATER QUALITY 4.2.1 Groundwater Sampling Schedule ASCI will continue to conduct quarterly groundwater sampling events at the Site for a minimum of four (4) consecutive quarters after mining operations have commenced. For each sampling event, groundwater samples will be collected from Site monitoring wells and submitted for laboratory analysis. A duplicate quality assurance/quality control (QA/QC) sample will be collected from one of the monitoring wells per event. Additional QA/QC samples (e.g., method blanks, laboratory control samples, matrix spikes, etc.) will be analyzed by the laboratory during batch analyses with results provided in the final laboratory reports.Any change to the groundwater quality monitoring schedule (i.e., reduction in sampling frequency) will be submitted to DRMS via TR for approval prior to implementation. 4.2.2 Groundwater Sample Collection Procedures Prior to sampling each well, depth to groundwater and total well depth measurements will be collected using a water level indicator to the nearest 0.01 foot. Groundwater will then be purged from the well utilizing a submersible pump with dedicated tubing or hand-bailed with a dedicated bailer. All non-dedicated equipment used to collect groundwater samples will be decontaminated with a detergent (e.g., Alconox® Detergent Powder) and distilled water solution prior to use at each monitoring well.Purged water will be collected in five(5)gallon buckets where water quality parameter readings for temperature, pH, specific conductivity, and total dissolved solids (TDS) will be collected. The total purge volume from the well will be recorded. Once groundwater stabilization is achieved (i.e., three consecutive readings within ten percent for each stabilization parameter) and/or a minimum of three (3) well volumes are removed, groundwater will be collected directly into laboratory-supplied containers with the preservative appropriate for the analysis requested, as applicable. Samples will be labeled, placed in a cooler with ice (cooled to 4°C),and stored until delivery to the laboratory accompanied by chain-of-custody documentation. 4.2.3 Laboratory Analysis of Groundwater Samples Groundwater samples submitted to the laboratory will be analyzed for applicable WQCC Regulation 41 INS Tables 1 — 4 analytes. The following analytical methods (or comparable methods)will be utilized by the laboratory to report water quality results. • Metals (Dissolved)by EPA Method 200.7 and 200.8 • Inorganic Anions by EPA Method 300.0+Calculation • Chromium by Standard Method(SM) 3500-Cr B + Calculation • pH by SM 4500-H-B • TDS by SM 2540-C Any change to the current analyte list for laboratory analysis (e.g., reduction of analytes) will be submitted to DRMS via TR for approval prior to implementation.