THE PROPOSED PRAIRIE CREEK MINE OPERATION:
The Site presently contains a near complete mill, three levels of underground workings, a fuel tank farm, office facilities, accommodation facilities and workshops. Existing buildings and structures will be upgraded and modernized. New facilities will include fuel-efficient low-emission power generation units, a kitchen/accommodation block, concentrate shed and an incinerator.
All mining will be performed from underground. Underground development and workings (about 5,000 metres) already exist on three levels, including the new 600 metre decline driven in 2006/07. Proposed production rates will reach 1,350 tonnes/day. Mining will initially be focused on the existing three levels (970, 930 and 870 m levels) of underground workings while a ramp is driven to access lower levels. Future underground development workings will include four new deeper levels accessed by a new haulage ramp. Mining methods will be mostly cut-and-fill on the narrow high grade vein structure with some room and pillar on the stratabound resource.
The mill, which was almost completely constructed but never operated in the early 1980's, will have a 1,500 tpd crushing capacity, with an installed jaw crusher, short head cone crusher, double-decked screen and a 2,000t ore bin.
A new dense media separation (“DMS”) circuit, designed by DRA Americas, at 85 tph capacity, will be installed into the crushing circuit to process -1/2” sized material. Indications from metallurgical testing are that the DMS plant will reject an average of 27% of the waste at minimal metal losses, hence mining input at maximum production rates will be 1,350 tpd and, after passing through DMS plant, will produce approximately 1,000 tpd of material to be processed in the grinding/flotation circuit of the mill.
Concentrates and Road Haul
A lead sulphide, zinc sulphide and lead oxide concentrate will be produced at the Prairie Creek Mine. The lead sulphide and oxide concentrates will be mixed prior to shipping to smelters. All concentrates will be bagged, stored under cover and trucked off-site in enclosed dump trucks over the winter road. CZN has applied for new Land Use Permits (LUP) for a re-aligned winter road from the Prairie Creek Mine connecting to the Liard Highway near Nahanni Butte. CZN has also applied for LUP’s for two new transfer facilities, one midway along the winter road, the other at the junction of the Nahanni road with the Liard Highway. The transfer facilities will provide temporary concentrate storage and will allow haulage to the Fort Nelson railhead during throughout the year.
Five new 1.5 MW diesel powered generator units will provide power and heat for the Site. These self-contained, pre-commissioned power generator units will be located adjacent to the mill. Maximum power load for the Site is estimated at 4,674 kW and diesel fuel will be the primary energy source required to operate the generators. These generators will be outfitted with heat recovery systems in order to maximize energy efficiency. The waste heat from the generators will be used to heat the surface facilities and supplement heat to the mine as well.
The Water Storage Pond is an existing large pond, originally intended in 1980 for tailings disposal, will be reconfigured, relined, expanded and recertified to form a two-celled Water Storage Pond. Mine drainage, treated sewage water and waste rock pile runoff will report to the first cell. Used water from the Mill will report to the second cell. The first cell will feed water to the Mill for mineral processing. Excess water from both cells will be sent to a water treatment plant. The treated water will discharge to the existing Catchment Pond before final discharge to the environment via an exfiltration system.
100% of the tailings from the mill will be placed underground in a form of paste backfill mix generated from the new paste backfill plant. The paste backfill plant is being designed by Kovit Engineering Ltd., of Sudbury, Ontario. The remainder of the DMS reject and mine development waste will report to a waste rock pile facility located near the mine.
At the end of the Mine’s life, the Site will be reclaimed. The underground development will be fully backfilled so as to help limit the movement of groundwater. The objective is to create a seal to minimize the movement of groundwater in the mine workings and limit the release of any contaminants. The waste rock pile will be covered with a clay-rich soil to limit infiltration and seepage. Site buildings and infrastructure, if deemed not to have any future use, will be dismantled and the Site will be returned to its natural setting.