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M-1977-410 <br />Technical Revision 10 <br />April 26, 2022 <br />14 <br /> <br />Pond 3A, a 6” diameter HDPE pipe conveys water from Pond 3A through Pond 3b and 3c to Pond #1, <br />where Caribou Effluent commingles with Cross Mine dewatering effluent. Pond #1, via a pumping system <br />feeds the Pilot Treatment Plant. <br />Appendix D provides details of the Pilot Plant Filtration System. Post 5 µm filtration, the water is treated <br />in sealed vessels packed with Graver MetSorb© HMRG media (Appendix E). Effluent from the system <br />meets regulatory permitted discharge standard; therefore, water is discharged into the Coon Track Creek <br />Permitted Outfall 001. <br />The Pilot Plant was installed and commission in November 2021 is located just to the southeast of Pond <br />#1, approximately 15 feet from the pond margin. The pilot system is housed in an insulated Connex trailer <br />with automated freeze protection. <br />The Pilot Plant treats the combined Caribou and Cross mines effluent from Pond #1 via four (4) stainless <br />steel, skid-mounted filter housings fitted with 5µ filtration bags (Ensero). A series of 4” schedule-80 PVC <br />pipe interconnect the filter housings and the Treatment Vessels. Inlet and Outlet Pressures of the <br />filtration system are measured and recorded. Pressure differential inform the operator of filtration bags <br />replacement needs. Filter bags normal operating pressure is 8 psi. <br />Filtration effluent is conveyed in a closed system via a 2”diameter hose into the pressure vessel loaded <br />with the Metsorb© adsorbent. Final polishing takes place in the ESS vessels through the Metsorb© <br />media. <br />In the normal configuration, the treated water is discharged from the vessel through a 2” diameter hose <br />for final environmental release through the monitoring shed which is located approximately 100 yards <br />southeast of the Connex through an 8” schedule-40 PVC to the permitted Outfall 001 to Coon Track Creek. <br /> <br />Monitoring, including a pH and temperature probe, Total Dissolved Solids (TDS) meter and a discharge <br />flow meter are located in the discharge shed (Figure 1). <br />The Pilot Plant current treats up to 150 gpm. The treatment capacity will be increase to handle the <br />maximum monthly average allowable discharge of approximately 300 gpm. <br />Pilot system automation features: <br />The Pilot Plant has been automated to increase predictability, consistency, reliability and control of <br />operations. The primary features of this automation system are a Variable Frequency Drive (VFD), which <br />controls the power and speed of the electrical motor systems (e.g., Pond #1 pump), and a Programable <br />Logic Controller (PLC), which allows a user to interface with and edit the settings of the systems described <br />below remotely. <br />The primary feature of the PLC is a real-time computer site display (Walchem) which reads and displays <br />measurements of the Cross Mine flow meter, Pond 1 pump speed and Pond 1 water level (controlled by <br />a pressure transducer), and measurements collected by the pressure transmitters before and after the <br />filter bag housings. The pressure drop between the influent source water and effluent (post-filtration) <br />water determines the frequency of filter bag changes (i.e., when to remove old, spent filter bags to be <br />replaced with fresh filter bags). While the manufacturer recommends a bag change at a drop of 2 psi, GIR <br />has found that the filter bags will last significantly longer than a 2 psi drop without either break-through <br />or sediment release. Analytics support extending the bag life and GIR will continue to monitor for optimal