For to-day's discussion our time is limited, so only

the dust control at the Primary Crushing Plant will be described.

The minesite crushing plant consists of one large jaw
crusher, two Tyrock screens, and a small 4' cone crusher, all
housed inside an essentially unheated building on the slope of
the moutain adjacent to the open “afte Ore throughput has gone
as high as 6,200 TPD, but normally is between 4,000 and 5,000 TPD
presently. The fragmented ore from the pit is discharged from the
pit trucks to a pan feeder, over a grizzly, and into a jaw
crusher with a 48 " jawset at 4" opening. The -4" discharge is
then transported by deep-trough idler conveyors onto the Tyrock
screens, the oversize discharging into the cone crusher. Cone
crusher discharge then recombines with Tyrock undersize result ing

in a crushed ore product of less than 3" nominal size.

Severe dust problems have existed in the past at the
crushing plant, particularly during the mid winter months when
the ore becomes very dry. The dust problems are not so pronouced
during spring, summer and fall when the ore is often moist and
wet due to melting of ice and snow in the pit; at such times
problems of a different nature (e.g-: sticking to chutes,

plugging screens) predominate.

In recent times considerable work has been initiated to
reduce dust levels in working areas at the Cassiar operations,
particularly now that asbestos has been shown to cause some very

serious health hazards.

The first dust control installed in the crushing plant

many years ago, consisted of relatively small ( less than 5,000

CFM) exhaust fans discharging to atmosphere and directly conn-