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M-1977-410 <br />Technical Revision 10 <br />April 26, 2022 <br />13 <br /> <br /> <br />Section 6: Pilot (Current) Treatment System <br />Pilot system and water flow path: <br />As presented in Section 5, the pilot test system was commissioned on site on November 2021. <br />The GIR site groundwater management and pilot treatment System consists of the following: <br />1. Groundwater effluent from the Caribou/Idaho tunnel reports to the permitted lined pond system <br />known as Ponds 3A, 3B and 3C system, were water flow cascades downgradient from Pond 3A <br />through 3B to 3C where a permitted gravity pipeline conveys all flows to Pond #1 <br />2. The gravity pipeline splits into two sections just upgradient of Pond #1 via a two-way valve <br />operated via float, where normal flows discharge into Pond #1 until pond #1 is full. Excess and <br />continued flow is conveyed via permitted pipeline to the Cross-underground workings known as <br />the Joliet Raise. <br />3. As a result of 2 above, Caribou groundwater effluent suspended solids are settled within the Cross <br />Mine underground workings. Caribou and Cross underground waters are thereby comingled. This <br />is effectively the same water comingling that takes place under normal operations of Pond #1 <br />were Caribou effluent from Pond 3C and Cross Mine groundwater from the pumping system <br />described under 4 below, are mixed prior to treatment. <br />4. Cross Mine dewatering is achieved via pumping from the Winze to Pond #1. The pumping system <br />dewater the Cross Mine to the lowest underground workings (400 Level). <br />5. A submersible pump installed in Pond #1 supplies the ENSERO Filtration System (Appendix D) and <br />the MetSorb© HMRG media vessel -closed and continuous feed- (Appendix E). <br />6. The ENSERO Filtration System consists of 4 inline filtration units with 5 µm filtration bags. Pressure <br />drop across the filtration units is monitored to determine if the filtration bags have reached solids <br />saturation <br />7. The post filtration effluent enters the MetSorb© HMRG Treatment Media (the polishing and <br />treatment elements). <br />8. Effluent from the MetSorb© HMRG Treatment Media vessels is conveyed via gravity pipeline to <br />permitted Outfall 001 where it is discharged into Coon Track Creek. <br />9. GIR has implemented several sediment reduction management strategies within the underground <br />workings. Those activities have been approved by DRMS on an on-going basis. <br />The Pilot Treatment System and Features are described in the following paragraphs: <br /> <br />The Pilot Plant treats waters from the Caribou Mine (Idaho Tunnel) portal effluent and the Cross Mine <br />Dewatering. <br />Cross Mine dewatering is achieved via a submersible pump installed in the Winze. Pump is currently <br />placed at the 4th level. The pump automatically controlled via a Level Transducer, Programable Logic <br />Controller and Electronic Flow Meter, which adjust the Pilot Plant inflow rate. <br />Caribou Mine (Idaho Tunnel) portal effluent that is conveyed via collection and pumping system (sump) <br />from the mine into Pond 3a. During December 2021 and January 2022, a cofferdam was constructed <br />inside the Caribou Mine, upgradient of the sump pump. The coffer dam functions as a settling basin. From