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Mining and Reclamation Permit Amend.-M-1988-112 <br /> Groundwater Management Plan Battle Mountain Resources,Inc. <br /> quality sampling and analyses. It is recommended that the current monitoring programs <br /> continue but with the following additions or modifications: <br /> 1) Replacement of monitoring wells in the event any are damaged or destroyed <br /> during installation of the slurry wall. Any replacement wells will be included in <br /> the respective water level measurement round and water quality sampling events <br /> that are currently conducted in the original well. For instance, if well M-20 is <br /> replaced, the replacement well (M-20R) would be measured weekly for water <br /> levels because that is the current prescribed measurement frequency for M-20. If <br /> well M-28 is replaced, the replacement well (M-28R) will be included in the <br /> quarterly water level measurement event. <br /> If well M-19 is damaged and replaced, the replacement well M-19R would be <br /> included in the quarterly water level measurement event and also in the quarterly <br /> water quality sampling event. <br /> 2) Addition of alluvial monitoring wells WP-3, and WP-5, and Santa Fe <br /> monitoring well WP-6 to the quarterly water level measurement round to provide <br /> additional information on the hydraulic response in the vicinity of the alluvial <br /> window, (located near the east portion of the slurry wall). Those wells should be <br /> included in the monitoring program for a period of 2 years following installation <br /> of the slurry wall. <br /> 3) Addition of Pit monitoring wells BF-1 and BF-2 to the quarterly water level <br /> measurement round. Those wells should be included in the monitoring program <br /> for a period of 2 years following installation of the slurry wall. <br /> 4) Placement of pressure transducers into monitoring wells BF-1, BF-4, M-16, M- <br /> 17, M-19, M-20, M-21, M-28, M-29, and WP-3 prior to installation of the slurry <br /> wall. The transducers should be programmed to measure water levels at 6-hour <br /> intervals beginning two weeks before construction of the slurry wall commences <br /> and continuing for four months following completion of the slurry wall. After that <br /> period, reduce the rate of measurements to once daily for a period of at least one <br /> year. <br /> 5) Convert all ongoing vertical water level measurements to the more current <br /> State Plane, Colorado South, North American Vertical Datum 1988 (NAVD88 <br /> projection). Historic measurements of water level elevations in the vicinity of the <br /> West Pit are based on State Plane, Colorado South, National Geodetic Vertical <br /> Datum 1929 (NGVD29) projection. The NGVD29 elevations are less accurate <br /> than the NAVD88 projection. Site monitoring wells were resurveyed in 2022. <br /> Therefore, BMRI is proposing to switch to NAVD88 for elevations and reporting. <br /> This will require adjustment of the prescribed elevations in the DP CO-45675 for <br /> wells BF-4 and BF5R inside of the Pit and alluvial extraction wells M-32 and <br /> M33. A comparison of the difference between the NAVD88 and NGVD29 <br /> projections for each of the site wells is shown on Table G-3. The average <br /> April 2025 13 Engineering Analytics,Inc. <br />