2024-05-23_REVISION - M2022009 (2)

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analysis of the baseline data within sixty (60)days of completion of the baseline sampling period. The baseline sampling period will end in the second quarter of 2025 with the fifth quarter of data for PZ-01. If during baseline sampling, any analytes exceed the reference values listed in Regulation 41 Tables 1-4, then MMMA will request a variance for that specific analyte and propose a numerical reference value for the Site with the Technical Revision. After completion of the baseline sampling period, sampling will be conducted on a twice per year basis. The twice per year sampling will be conducted during March and September of each year and the results will be reported to the Division with the Site's groundwater elevation data according to the following schedule: • March sampling report due by May 1St of every year. • September sampling report due by November 1St of every year. If there is evidence of groundwater discharges exceeding applicable groundwater standards or permit conditions imposed to protect groundwater quality, the Miner will submit a written report to the Division within five (5)working days of receiving the data. 6.0 GROUNDWATER ELEVATION MONITORING AND MITIGATION This section supplements the Groundwater Model Report which recommends an underdrain mitigation structure south of Cell 3 and is described in the Groundwater Model Report. For more detail on the proposed underdrain, see the recommendations section of the Groundwater Model Report. The Site monitoring wells will be measured monthly to identify potential changes in alluvial groundwater elevation associated with mining and reclamation activities. Baseline data collected from the monitoring program will provide a range and measure of variability of relative water levels associated with pre-mining groundwater conditions. Experience at other mines in similar geologic settings has found that groundwater levels tend to fluctuate being highest in the summer irrigation season and lowest in the winter and early spring. If, during mining or reclamation, the relative seasonal groundwater elevation at the upgradient monitoring wells (PZ-20, PZ-25, and PZ-27) differs from maximum conditions by more than three (3) feet, and the condition was not observed during baseline monitoring, or if the miner receives a complaint from a well or property owner, then the Miner will evaluate the cause and take action within seven (7)days and notify the DRMS. After the DRMS has been notified, the Miner will review the data and available information and submit a report to the DRMS within 30 days. The evaluation will include discussions with the well owner who has contacted the miner regarding a concern and review of baseline data from the well and vicinity to evaluate whether changes may be due to seasonal variations, climate, mining, slurry wall lining or other factors. The report will identify the extent of potential or actual impacts associated with the changes. If the extent of groundwater changes due to mining or reclamation activities is determined to be a significant contributing factor that has or may create adverse impacts, the mining associated impacts will be addressed. The Miner will begin implementing one or more mitigation measures if mining and reclamation activity is determined to be a significant factor to groundwater changes requiring mitigation. Mitigation measures may include, but are not limited to: ➢ Placing water in a recharge pond to raise groundwater levels around the well. ➢ Constructing a local clay liner at the edge of the mine Cell (i.e. between the dewatering point and the well) in order to raise water levels on the well side of the liner and mitigate dewatering effects. Monitoring and Analysis Plan—Monarch DENM Gravel Mine -5- March 2024