slumping and cracking of the dumps dictate the need
for good maintenance practices. Haul lengths vary
depending on location, with averages of 2500 ft
(762 m) one way, uphill hauls comprising about 50%
of the production time.

Tire wear is a major concern during spring and
summer, as the combination of water and extremely
sharp-edged rock fragments cause serious tire damage
unless the roads are well graded and drainage ditches
installed. A revised tire maintenance program begun
one year ago with the assistance of a major tire supply
company is already paying dividends. It is proposed
to extend this tire maintenance program whereby a
contract will be entered into with a tire company and
tires will be supplied on a unit-cost-per-hour basis.

Chains are used on graders and some support ve-
hicles, such as the mobile lubrication truck which serv-
ices the equipment in the field. Major repairs to trucks
are carried out in the mine garage, located in the pit.
The facility consists of five truck bays, a welding bay
and a steam bay.

Ore Mining

Mining of ore is carried out 260 days per year, three
shifts per day, with two days of scheduled mainte-
nance each week on the crushing plant and tramline.
The daily production rate is 5000 tons, with an aver-
age recoverable mine grade (R.M.G.) of 9%.

Drilling of the ore and serpentine host rock is per-
formed with a diesel-powered Robbins R108, mounted
on an International TD25 tractor, utilizing a 9-in.-dia-
meter hole and capable of drilling 60 ft (18.2 m) if
required. Prior to drilling, the area is levelled and
prepared for the surveyors to mark out the required
drill pattern. Patterns vary from 22 ft (6.7 m) by 22 ft
in the summer to 18 ft (5.5 m) by 18 ft in the winter
months on a 30-ft. (9.1-m) deep bench. The top 3 to 4
feet of the ore bench are saturated with water during
the summer, therefore, once freezing conditions pre-
vail, this portion freezes and is very difficult to frag-
ment during blasting. On occasion, holes 8 ft (2.4 m)
deep are drilled between each row of production blast
holes, charged with 25 lb of explosives and blasted with
the main blast to try to alleviate the problem of large
blocks of ore being produced after blasting. This
blocky ore is extremely difficult to fragment in the
jaw crusher. To help reduce orebody saturation caused
by water, ditches and culverts are installed in the sum-
mer to control and direct water to the dewatering
sump.

FIGURE 6 — Double-side shovel loading after a typical blast.

The ore mining sequence is dictated by the sales
commitments, and a three-month mining plan is drawn
up each month and revised as required. Blending of
ore in the pit is practised under the supervision of the
mine geologist, with all information required being
recorded in the mine foreman’s office.

Contamination of ore by foreign objects cannot be
tolerated and great care is taken to ensure cleanliness,
both on the ore bench and during the ore crushing
cycle.

No subgrade drilling is practised, as the ore is
relatively easy to blast at a normal charging ratio of
0.4 lb per ton. Whenever possible, ANFO is used, with
excellent results. Drill holes are not normally pumped
in the asbestos ore, as no polyethylene liners can be
used. A special explosive, “Cilgel”, has a package
covering that conflagrates during the blast. All blast
initiations are carried out using a capped fuse attached
to primacord in preference to electric blasting, thus
preventing ore contamination by lead wires. After the
blast, the bench is levelled to ensure that during winter
any heavy snowfall can be cleaned off the ore prior to
sending it to the crushing plant. Fragmentation of the
asbestos ore is controlled to ensure maximum rejection
at the mill concentrator, thus ensuring that no un-
necessary rock is dried or milled. A 30% rock rejec-
tion is the scheduled target at the concentrator.

Loading of the ore is carried out with a Caterpillar
992 front-end loader, equipped with a 10-cu.-yd bucket
and beadless tires (linked tracks similar to tractor
pads), which have proved effective in reducing tire
spin, thus reducing rubber contamination in the ore.
Whenever possible, serpentine waste rock is made
available to enable the loader to load ore and waste.
As the loader is radio equipped, the crusher operator
can direct the ore trucks to waste and inform the
loader operator when the next requires ore.

The ore haulage fleet consists of five 50-ton Wabco
trucks, equipped with VTA 1710 12V 635-hp Cummins
engines and Allison 6061 transmissions. Normally, two
trucks are running during the ore cycle. If waste is
available close by, an additional truck is added to the
fleet. Truck counts are taken of the ore hauled to the
crusher; a survey check is made and the ore is weighed
at the mill. This has established that the 50-ton Wabco
trucks average 44 tons per load. Haul roads are kept
at an 8-10% gradient whenever possible. Salt and
sand are used during winter months and crushed
gravel is spread on the main footwall haul road to
ensure good drainage.

Dewatering

Pumping is required to ensure that the ore is kept
as dry as possible (so that less fuel will be required
for ore-drying) and to ensure good access to the ore
during the spring melting and the summer rain
periods. Snow is normally cleaned from the catchments
and the pit area in April to minimize the inflow of
water from the snow melt. A truck equipped with a
4000-gallon tank is used to haul water out of the pit
until such time as the electric submersible pumps and
the 8-in.-diameter pipeline can be installed (in May)
without freezing problems. A 2250B Flygt pump, rated
at 700 gallons per minute, with a combined static and
friction head of 215 ft (65.5 m), is installed in the
sump at the pit bottom (5570-ft elevation on Phase 7).
The pump is installed on a base made from 6-in. ‘Tl
beams to ensure that the suction inlet is clear of the
sump bottom, as the long asbestos fibre tends to block

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