THE COLLIERY GUARDIAN

AND

JOURNAL OF THE COAL AND IRON TRADES.

Vol. CXII.

FRIDAY, SEPTEMBER 1, 1916.

No. 2905.

Coal Mining under the River Waikato and Lake Hakanoa, N.Z.

In the New Zealand Alines Department Annual
Report for 1915 by the Chief Inspector of Mines, Mr.
Frank Reed, appears an interesting account of coal
mining operations under the River Waikato and Lake
Hakanoa at the Taupiri Extended Colliery, where on
July 6, 1915, a serious irruption of sand and water
occurred. This wa.s followed by an important arbitra-
tion case under the safety provisions of the Coal Alines
Act, the contending parties being the inspector of
mines and the mine manager.

During the past year considerable attention has been
given to the cover at this mine. The dowmcast shaft is
164 ft. deep, 81 ft. of which is cylindered mostly through
running ground; and the upcast shaft is 204ft. deep,
of which 106 ft. is likewise cylindered. The strata
penetrated in each shaft was 80 ft. and 90 ft. respec-
tively of permeable pumice sand and mud, underlying
which is jointed claystone (fireclay), which forms the
roof to the coal seam. In the deeper portions of the
mine an upper seam exists in the claystone, but this

more or less saturated with water, which constitutes a
dead weight without any supporting strength whatever.

About 20 years ago, under different management,
mining was extended under Lake Hakanoa until at one
point only 56J ft. of cover existed between the roof of
the workings and the lake bed, above which the water
level is about 10 ft. On two or more occasions during
these mining operations running sand was encountered
at the roof of the coal seam. In one case a dam was
constructed as a precautionary measure.

Several years ago workings were also extended under
the River Waikato to the rise and approaching the coal
barrier between the Extended and the same company’s

— Taupiri Coal TCtne.s Ias

iHHkHH

Th is	#4	A?

the repot t tk#	of bp tfo r^S r^ar-di^

cover and	wafer tyvd	/	•

. • .

•A

— Plaft—
----OF A PORTION OF------ W®
OLD TTFTDER -WATER WOJIKTFGS

---AT --

---EXTEFTJOEJD COLLIERY--

--- SHOWING --- :>i

---THE EOSITIOJY OF PROPOSED RAFTS
------------- AGAINST----------/
--------IRRUPTIONS OF WATER. --- t /

X X.

(£X Tfn w

1W
noumL
□□□□□□

fir. Yi'-S'

OXti'ii r ,

------ --------------------------

Tr<rpose.cL D^rnS _	_	___aJjoivn -th

ZF’cClAGi________	___ _	___ _	.»

-I'ojpG. TiA-tAsL^e. jroajRa _	••	•»

Fig.. 1.—Plan of Part of the Workings.









The following reference to the Taupiri Extended
Colliery from the report of the Chief Inspector will be
of special interest to those concerned in under-water
mining operations, but the risks taken during the
number of years since the workings were made under a
different management and inspectorate may not be
commended.

It is somewhat remarkable that a mine having in
some parts no other cover than a shell of coal left on
the roof, overlaid by sand and water, did not cause
trouble earlier.

has been eroded in the shallow south-eastern section of
the mine. The workings are situated under a plain,
which is intersected by the River Waikato, and depressed
at Lake Hakanoa; geologically, this plain covers a
buried valley. The underlying coal measures, which
rise towards the shafts and the lake, are inclined at
about 1 in 10, and have been eroded by the ancient river
to such an extent that little or no rock cover to the coal
seam remains in the south-east portion of the mine, as
shown by the vertical sections (fig. 2). The overlying
formation now consists chiefly of pumice sand and mud,

Ralph’s Colliery. Above the face of a bord, situated
almost directly under the eastern edge of the river,
only 71 ft. of cover separates the roof of the bord from
the river bed. The cover in this immediate locality is
in all probability nearly all pumice sand and mud,
except for a few feet of coal, which has been left on
the roof of the workings throughout the mine as a pre-
cautionary measure. It is important to note that in
New South AVales all Crown coal leases now contain a
provision that in all workings under the ocean, or under
river, lake, estuary, or tidal waters, no coal shall be