The work of connecting Liverpool with Birkenhead by means of a railway
tunnel is now an almost certain success. It is probable that the entire
cost of the tunnel works will amount to about half a million sterling.
The first step was taken about three years ago, when shafts were sunk
simultaneously on both sides of the Mersey. The engineers intrusted
with the plans were Messrs. Brunlees & Fox, and they have now as their
resident representative Mr. A.H. Irvine, C.E. The contractor for the
entire work is Mr. John Waddell, and his lieutenant in charge at both
sides of the river is Mr. James Prentice. The post of mechanical
engineer at the works is filled by Mr. George Ginty. Under these chiefs,
a small army of nearly 700 workmen are now employed night and day at
both sides of the river in carrying out the tunnel to completion. On
the Birkenhead side, the landward excavations have reached a point
immediately under Hamilton Square, where Mr. John Laird's statue is
placed, and here there will be an underground station, the last before
crossing the river, the length of which will be about 400 feet, with up
and down platforms. Riverward on the Cheshire side, the excavators have
tunneled to a point considerably beyond the line of the Woodside Stage;
while the Lancashire portion of the subterranean work now extends to
St. George's Church, at the top of Lord street, on the one side, and
Merseyward to upward of 90 feet beyond the quay wall, and nearly to the
deepest part of the river.
When completed, the total length of the tunnel will be three miles one
furlong, the distance from wall to wall at each side of the Mersey being
about three-quarters of a mile. The underground terminus will be about
Church street and Waterloo place, in the immediate neighborhood of the
Central Station, and the tunnel will proceed from thence, in an almost
direct line, under Lord street and James street; while on the south side
of the river it will be constructed from a junction at Union street
between the London and Northwestern and Great Western Railways, under
Chamberlain street, Green lane, the Gas Works, Borough road, across the
Haymarket and Hamilton street, and Hamilton square.
Drainage headings, not of the same size of bore as the part of the
railway tunnel which will be in actual use, but indispensable as a means
of enabling the railway to be worked, will act as reservoirs into which
the water from the main tunnel will be drained and run off to both sides
of the Mersey, where gigantic pumps of great power and draught will
bring the accumulating water to the surface of the earth, from whence
it will be run off into the river. The excavations of these drainage
headings at the present time extend about one hundred yards beyond the
main tunnel works at each side of the river. The drainage shafts are
sunk to a depth of 180 feet, and are below the lowest point of the
tunnel, which is drained into them. Each drainage shaft is supplied
with two pumping sets, consisting of four pumps, viz., two of 20 in.
diameter, and two of 30 in. diameter. These pumps are capable of
discharging from the Liverpool shafts 6,100 gallons per minute, and from
the Birkenhead 5,040 gallons per minute; and as these pumps will be
required for the permanent draining of the tunnel, they are constructed
in the most solid and substantial manner. They are worked by compound
engines made by Hathorn, Davey & Co., of Leeds, and are supplied
with six steel boilers by Daniel Adamson & Co., of Dukinfield, near
Manchester.
In addition to the above, there is in course of construction still
more powerful pumps of 40 in. diameter, which will provide against
contingencies, and prevent delay in case of a breakdown such as occurred
lately on the Liverpool side of the works. The nature of the rock is
the new red sandstone, of a solid and compact character, favorable for
tunneling, and yielding only a moderate quantity of water. The engineers
have been enabled to arrange the levels to give a minimum thickness of
25 ft. and an average thickness of 30 ft. above the crown of the tunnel.
Barges are now employed in the river for the purpose of ascertaining the
depth of the water, and the nature of the bottom of the river. It is
satisfactory to find that the rock on the Liverpool side, as the heading
is advanced under the river, contains less and less water, and this the
engineers are inclined to attribute to the thick bed of stiff bowlder
clay which overlies the rock on this side, which acts as a kind of
"overcoat" to the "under garments." The depth of the water in one part
of the river is found to be about 72 ft.; in the middle about 90 ft.;
and as there is an intermediate depth of rock of about 27 ft., the
distance is upward of 100 ft. from the surface of low water to the top
of the tunnel.
It is expected that the work will shortly be pushed forward at a much
greater speed than has hitherto been the case, for in place of the
miner's pick and shovel, which advanced at the rate of about ten yards
per week, a machine known as the Beaumont boring machine will be brought
into requisition in the course of a day or two, and it is expected to
carry on the work at the rate of fifty yards per week, so that this year
it may be possible to walk through the drainage heading from Liverpool
to Birkenhead. The main tunnel works now in progress will probably be
completed and trains running in the course of 18 months or two years.
The workmen are taken down the shaft by which the debris is hoisted, ten
feet in diameter, and when the visitor arrives at the bottom he finds
himself in quite a bright light, thanks to the Hammond electric light,
worked by the Brush machine, which is now in use in the tunnel on both
sides of the river. The depth of the pumping shaft is 170 feet, and the
shaft communicates directly with the drainage heading. This circular
heading now has been advanced about 737 yards. The heading is 7 feet in
diameter, and the amount of it under the river is upward of 200 yards on
each side. The main tunnel, which is 26 feet wide and 21 feet high, has
also made considerable progress at both the Liverpool and Birkenhead
ends. From the Liverpool side the tunnel now extends over 430 yards, and
from the opposite shore about 590 yards. This includes the underground
stations, each of which is 400 feet long, 51 feet wide, and 32 feet
high. Although the main tunnel has not made quite the same progress
between the shafts as the drainage heading, it is only about 100 yards
behind it. When completed, the tunnel will be about a mile in length
from shaft to shaft. In the course of the excavations which have been so
far carried out, about 70 cubic yards of rock have been turned out for
every yard forward.
Ten horses are employed on the Birkenhead side for drawing wagons loaded
with debris to the shaft, which, on being hoisted, is tipped into the
carts and taken for deposit to various places, some of which are about
three miles distant. The tunnel is lined throughout with very solid
brickwork, some of which is, 18 inches thick (composed of two layers
of blue and two of red brick), and toward the river this brickwork is
increased to a thickness of six rings of bricks--three blue and three
red. A layer of Portland cement of considerable thickness also gives
increased stability to the brick lining and other portions of the
tunnel, and the whole of the flooring will be bricked. There are about
22 yards of brickwork in every yard forward. The work of excavation up
to the present time has been done by blasting (tonite being employed for
this purpose), and by the use of the pick and shovel. At every 45 ft.
on alternate sides niches of 18 in. depth are placed for the safety of
platelayers. The form of the tunnel is semicircular, the arch having a
13 ft. radius, the side walls a 25 ft. radius, and the base a 40 ft.
radius.
Fortunately not a single life has up to the present time been lost in
carrying out the exceedingly elaborate and gigantic work, and this
immunity from accident is largely owing to the care and skill which are
manifested by the heads of the various departments. The Mersey Tunnel
scheme may now be looked upon as an accomplished work, and there is
little doubt its value as a commercial medium will be speedily and fully
appreciated upon completion.
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