5.   MINING

5.4.1  

Hillendale Mine

A feasibility study for Hillendale Mine evaluated five different mining methods. On a net present cost basis it was found that a hydraulic monitoring method was the least expensive, with the next cheapest being an excavator – pumping system combination. The hydraulic mining method, which has been successfully used at the Hillendale Mine for the last four years, is also proposed to be used for the Fairbreeze Project C and Fairbreeze Project C Extension deposits.

Description of Hydraulic Mining Method: The Hillendale Mine hydraulic mining method consists of a series of water monitors which are used to direct a continuous high pressure (up to 40 bar at the Hillendale mine) water jet onto the face to undermine it, thus causing it to collapse. When sand from the face falls in blocks, the water is used to break up the material into a slurry which then gravitates into a satellite pump station situated at an elevation well below the lowest planned mining elevation.

Transport of the slurry from the mining area by means of a trench system is utilised. A satellite pump transfers the slurry into a plastic-lined, V-shaped surface trench down which it gravitates to a central sump area, located next to the PWP. This transport method has proved to be very successful at the Hillendale operation. A caisson structure protects the pumps in the sump area, from where the RoM is pumped into surge bins with a capacity of 1,000m³ to guarantee a constant supply and also to control the density of the feed to between 35% and 45% solids.

The mining contractor installed the required mining equipment at the start of the Hillendale mining operations during 2001. The contract with the mining contractor at the Hillendale Mine was wound up in November 2005 and Ticor SA now perform owner operator mining at Hillendale Mine.

The maximum Hillendale production rate is planned to be 1,200tph – four monitors can be operated simultaneously, with each monitor producing 300tph and two additional monitors on standby. The mining production schedule is driven by smelter demand requirements, which define the ilmenite requirements.

Mine production is between 8,000ktpa and 9,000ktpa.

Mining at the Hillendale operation takes place very close (up to 10m distance from fence lines in plan view) to inhabited properties. Special care is required when mining in these areas adjacent to these properties to ensure that no instability of the highwall occurs that is abutting onto these properties. At Hillendale a service road is positioned next to the inhabited property fence line and service pipelines for high pressure water and other services are positioned on the property fence side of the service road.

5.4.2

Tiwest JV

The Tiwest JV mining operation has a current capacity of approximately 21Mtpa of ore. Dredging operations account for approximately 16Mtpa and the remainder (5Mtpa) is sourced via scraper operations in a dry mining operation. Combined production of the HMC of up to 800kt is transported by road to the dry separation plant at Chandala.

The mining operations at Cooljarloo are divided into two separate entities, the South Mine and the North Mine, each employing a different mining method.

South Mine: The mining operations in the South Mine consist predominantly of a dredging operation. The vegetation is first stripped within the mining limits. This stripping/clearing is undertaken in preparation for the overburden stripping by a mining contractor using track dozers. Vegetation clearing is normally 50 – 100m in advance of the overburden stripping operations. Once the vegetation is removed the mining contractor utilises scrapers to remove the topsoil to a nominal depth of 0.3m, normally in two cuts one of 0.05m and the second of 0.25m. Where possible this topsoil is placed directly onto ‘land formed’ areas to take advantage of the active seed load.

Overburden removal is also undertaken by a mining contractor, using an excavator and haul trucks. The overburden is removed in flitches of up to 4m in depth and in minimum working widths of 50m. Mining of the overburden cycles between flitches is aimed to maintain ore exposure of at least 6 – 8 weeks in front of the dredges. This system also maintains a blend of overburden on the dump to maintain the dump integrity.

Overburden is hauled to the rear of the dredge pond and dumped on the “beach” to complete the ‘land form’. After the removal of the overburden, the ore mining is undertaken by Tiwest JV using two dredges working in a purpose built pond to pump ore directly to a floating concentrator. The smaller dredge mines to a maximum depth of 9m ahead of the larger dredge which mines to a depth of 25m. Installed dredge capacity currently exceeds the concentrator capacity. Oversize rocks and debris are removed by trommel prior to the concentrator and sand tailings are returned to the mining area for use in rehabilitation. Heavy minerals are extracted from the sands and clays and pumped from the concentrator to stockpiles.

North Mine: The North Mine is currently located approximately 5km to the north of the dredging operations in the South Mine. The mining operations are based upon a dry mining operation using track dozers to firstly remove and stockpile the vegetation. Topsoil is then removed similar the South mine operations, whilst the thin layers of overburden are removed and placed by a fleet of elevating scrapers. Ore is then removed with the same scraper fleet which deposits the ore into a hopper for feed to a trommel to remove the clay and debris. Sand is then transported to a land-based wet concentrator for separation of the heavy minerals.

As the mining progresses through the orebody, sand and clay are returned to the void and the surface reformed prior to the spreading of topsoil and eventual rehabilitation. The mining methods currently employed at each of the current operational areas are appropriate for the orebodies being exploited.

The mining contracts for overburden removal in the South Mine and for mining operations in the North Mine are currently under review and re-tender. Whilst this will not alter the current methodology in both areas it is expected that pricing will increase in line with current increases in labour and fuel costs. Productivity in these areas will however, likely increase with the change of contractor. Current equipment on the most part is aged and availability is low with the incumbent contractor reluctant to upgrade at this time of retender given the uncertainty of tenure.