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Note: The following information, addressing the caustic soda treatment system, has been superseded, but is
<br />retained as historic information -Mine water is pumped from underground sump areas, and discharges to the
<br />delivery line where the flow is metered. As the mine water is discharged from the delivery line, it is injected with
<br />reagents, subsequently mixed, and is then routed through the treatment pond system to allow iron and sediments to
<br />• precipitate and settle-out. Immediately prior [o final discharge from the facility, a pH reducing reagent may be injected
<br />into the treated water, if required. After treatment, water flows from the treatment ponds through a dischazge ditch to
<br />Fish Creek. A portable structure, approximately 20 x 8 x 8 feet, placed on the north light-duty road for the easternmost
<br />cell of the treatment facility, houses storage containers of NaOH and equipment for metering and injecting the reagent.
<br />An additional stmcture, approximately 32 x 8 x 8 feet, will be placed adjacent to this existing stmcture to house a larger
<br />storage container for NaOH. A smaller portable structure, approximately 8 x 8 x 6 feet, placed on the west light-duty
<br />road for the westernmost pond, houses storage containers of HZSO, and equipment for metering and injecting.
<br />Overhead power is provided to all of these structures, via pole-mounted lines from the substation. Three to five
<br />additional poles will be set to provide power to the remote monitoring equipment.
<br />In the Spring of 2006, an electro-coagulation system replaced the existing sodium hydroxide (caustic) system for
<br />treatment of water pumped from the Western Mining District at the Fish Creek Borehole. Safety, maintenance, and
<br />cost benefits were the primary reasons for replacing the existing caustic treatment system. The electro-coagulation
<br />system applies a constant electrical charge to the incoming mine water, ionizing particulates in the water feed
<br />stream, and causing the charged particles to agglomerate (coagulate), and drop-out. The existing treatment ponds
<br />will still be used to capture the precipitates from the treatment process.
<br />The system is essentially a modular system, housed in two metal shipping containers; the equipment is housed in a
<br />40 x 8 x 10 foot high container mounted on poured concrete piers; the other 25 x 25 x 24 foot container, containing
<br />the process tank, valves, and flow metering equipment sets on a 6-inch thick monolithic concrete pad. An 8 x 19
<br />foot, 5,000 gallon water tank is installed in one comer of the second container. A treated product line discharges
<br />from the tank container tank to the first settling pond. The containers housing the system aze located immediately
<br />east of the existing caustic soda and electrical control buildings. In order to handle both norntal discharge and any
<br />potential overflow from the treatment settling ponds, a 200-foot 12-inch bell and spigot PVC pipe is attached to the
<br />• discharge culvert from the third and final treatment pond, which formerly drrected treated water through Site 115 to
<br />Fish Creek. This 12-inch PVC discharge pipe ties back into the southernmost Fish Creek borehole pump shaft,
<br />which is no longer in use, to carry the water back underground.
<br />In order to be able to run the borehole pumps at rated capacity, while regulating discharge from the treatment ponds at a
<br />lower rate, a recvculation line has been installed in the system. The recirculation line is a 4 inch HDPE pipe, buried
<br />underneath the road on the east side of the east cell that terminates at the Fish Creek Ventilation Borehole, where mine
<br />water can be dischazged back into the mine. The recirculation line ties into the mine water dischazge line in a manhole
<br />placed in the north berm of the eastern cell. Also within the manhole are valves to direct flow to the recirculation line,
<br />and flow meters for monitoring the mine water discharge line and the recirculation line. When the line and manhole are
<br />no longer needed, they will be removed from the site as part of the fmal reclamation process.
<br />Installation of remote monitoring equipment at sites upstream and downstream of the Borehole dischazge point, and at
<br />the effluent of the treatment pond, as shown on Map 13a, provide a more efficient means for monitoring the water
<br />quality in Fish Creek. Automated sample results, along with system operating parameters aze relayed to TCC's
<br />Administration Building where they can be reviewed. Current information is, therefore, available for regulating the
<br />treatment process at the borehole facility. TCC may install additional monitoring equipment in the ponds to further
<br />enhance the treatment process.
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<br />MR07-216 2.05-50.1 05/28/07
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