Page 56 - 00 Volume 5 The Mine
P. 56
TIME LOST
Considerable time has been lost because the
timber blocked the dredge pumps, which had smaller
impellor passages than intakes.
A floating sluicing plant was built to loosen the
stumps and logs and the timber was gathered up on a
barge. This method proved satisfactory, he continued.
Larger stumps were dragged towards the stopbanks by
means of a tractor winch. Prolific growth of rushes on
the lake bed mud also contributed to stoppages and
hormone spray was used with some success. New
pumps with larger impellor passages had been
ordered, Mr Nanson said.
Another setback was the collapse of the stopbank
between the present dredging pond and the lake
proper.
The breaches had been repaired quickly with the aid
of all possible land equipment pouring soft clay,
fireclay, into the gaps to form extra banks and
there had been a negligible movement of water.
The lake was ept at a fairly constant level throughout
the project, Mr Nanson said.
SCHEME CHECKED
The Ministry of Works had been called in to
examine and check the whole scheme after the
stopbank failures to ensure the safety of the project in
view of the huge resources at stake. Although the
Department of Mines had not received the final
recommendations from the Ministry of Works, Mr
Nanson said he understood the present scheme was
Coal from the pit was transported to the railhead by favoured, although perhaps with some changes.
a rubber conveyor belt. He said it would probably be desirable to build
valuable coal seam at the Lake Kimihia opencast another stopbank outside the existing one.
coal mining project, has been moved by the "It would cost about £70,000 but it would definitely
£150,000 suction dredge which went into operation be worth it to make sure of winning the coal", he said.
last year. Dredging the overburden had been chosen because
This was stated by Mr G. L. Nanson, project it was cheaper than dry stripping. The latter would also
involve the working of high, and consequently
manager of Downer and Company, contractor to the
Government for the supply of coal from the mine, in
an address to the South Auckland branch of the New
Zealand Institute of Engineers in Hamilton last night.
The dredge works in a pond, stop-banked from the
lake proper, sucking out the useless overburden and
casting it into the lake.
It is estimated that there are 2,000,000 tons of coal
to be won from the lakebed.
Even with the depth from lake level to the coal
seam of up to 200 feet Kimihia was one of the most
economic mines in New Zealand and was capable of
producing good cheap coal, Mr Nanson said.
One of the main difficulties encountered with the
dredging so far was the amount of timber and
stumps on the lake bottom - no doubt the remains of
a drowned forest.
There are logs of kauri and other timbers strewn all One of the several pumping stations spread along the
over the place, said Mr Nanson.
inner wall of the coffer dam.
