Proposed Prairie Creek Mine Operation:
The Mine 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.
Proposed Underground Development to Extract Measure and Indicated Resources
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
Lead sulphide, zinc sulphide and lead oxide concentrates 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. LUPs for the winter road re-alignment and two transfer faciltiies have been issued.
Haulage Route for Mineral Concentrate to Fort Nelson Railhead
Canadian Zinc has been working with a number of experts in the transportation business to identify optimum transportation routes and methods, along with the associated costs. The transportation plan utilized in the 2012 PFS envisaged the use of the access road from the mine site to the Liard Highway only in the winter months of each year, both for the outbound transportation of concentrates and for the inbound transportation of equipment and supplies, including diesel fuel. This winter road plan would necessitate a large investment in working capital to finance consumables and supplies and also a large build up in concentrate inventory awaiting transportation and sale, and would also involve a major mobilization and logistical exercise.
Accordingly, in pursuit of possible improved economics, consideration is now being given to the construction and use of an all season road which would enable the transportation of both supplies and concentrates in smaller volumes spread throughout the year.
An all season road would also have the potential to reduce energy costs and would enable the consideration of more environmentally-friendly alternative energy sources, as local gas fields in the area may be producing LNG in the near future, which could reduce the Mine’s reliance on diesel fuel. An all season road would also have environmental benefits in that there would be much less traffic in winter, and therefore a lower risk of any accidents or spills, and would also provide the potential to promote tourism in the area and thus create long term benefits for the region.
Incorporation of an all season road for future operations would have significant financial implications, both in additional capital cost but also in potential savings and lower finance costs. Because of the environmental and economic benefits indicated from the operation of a year round road, early in 2014 the Company applied to the regulatory authority for a Land Use Permit for an all season road into the Prairie Creek mine. The all season road application is presently in Environmental Assessment and Company is submitting it’s required Developer’s Assessment Report shortly. In tandem with this the Company is currently finalizing the design and cost estimates of a potential all season road for inclusion into the capital cost schedule of the Prairie Creek Project, along with incorporating the consequent reduction in operating costs.
Five new 1.5 MW diesel powered generator units will provide power and heat for the Mine Site. These self-contained, pre-commissioned power generator units will be located adjacent to the mill. Maximum power load for the Mine 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.
Water Quality and Management
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.
Proposed Water Storage Pond Showing Cells
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 Mine 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. Mine Site buildings and infrastructure, if deemed not to have any future use, will be dismantled and the Mine Site will be returned to its natural setting.