The Sun.
London, England, 1858-12-01 00:00:00

MAIN DRAINAGE OF LONDON.-THE
NORTHERN 111011-LEVEL SEWER.

(From the Builder.)

The drawings and specification of the first portion
of the work of the metropolitan main drainage are
in the hands of surveyors, who are taking out the
quantities, in order that tenders may be received
on the 16th of next month; and, considering the
great importance structurally of the works which
will be in progress in all parts of London during
the next 3-ear, and that the details of their execu-
tion may deserve to be referred to as precedents,
our readers will perhaps be glad to have such par-
ticulars as we have been able to gather. The
work now specified comprises construction of the
Northern. High-level Sewer, from the point of tem-
porary outfall on the River Lea, at Old Ford, to
Southampton-road, near Hampstead; of a shorter
sewer, branching from the main line, northward,
at a point near the outfall, and extending thence,
partly along the course of the present Hackney-
brook sewer, to High-street, Honierton ; and of a
sewer in the Lower Olapton-road, besides the river
wall at the outlet, tumbling-bay and storm
outlets, overflow, and penstock chambers and
buildings, side-entrances, ventilators, and other
matters of detail, as well as the removal of
surplus earth to the ground eastward of the
Lea on the line of the main out fall sewer—of
which the works in chief will be the subject of a
future contract. The Metropolitan Board have
given notice, by advertisement, of their intention
to proceed with these latter works ; and the draw-
ings and specification are expected to be ready in
March next. The whole of the works of the metro-
politan drainage, it will be recollected, were to be
divided into eleven contracts, seven of the number
being for as many sewers within the populous dis-
trict, and the other contracts being for the reser-
voirs and the outfall sewers.

The Northern High-level Sewer Works, the sub-
ject of present attention, were roughly estimated to
cost, with land and compensation, £150,000, and
they will extend over 8 miles 4,295 feet, or there-
abouts, of ground ; the main line being somewhat
more than seven miles, and the shorter line, called
the Wicklane Branch, rather more than one mile.
The outlet will be close to that, at present, of the
Hackney-brook, which discharges itself into the
Lea at a bend of the stream near to Old Ford-road.

The two branches nearly entircle the Victoria-park;
with other ground; and the Wicklane branch, at
its upper end, will touch the North London Rail-
way at a point little over 1,600 feet distant east-
ward from the Hackney station, where the main
line of sewer will cross under that railway.
Nearer to the point of outfall the railway inter-
sects each branch; Sir George Duckett's canal also
intersects ; and a portion of one branch being carried
above the level of the ground in an embankment,
and at the railway so that the sleepers supporting
the rails will be about on a level with the crown
of the arch of the sewer (the brickwork to be
brought up to support the ends of iron girders upon
which the sleepers are to rest, whilst the traffic of
the railway is not to be interrupted), we may well
suppose that some of the anticipated difficulties of
metropolitan drainage will be exemplified. Gene-
rally speaking, the lines are made to coincide with
those of existing streets and roads, and there ap-
pear to be but four or five houses which will require
to be taken down and rebuilt.

On the completion of the outfall to Barking Creek
the sewage will pass the River Lea by means of an
aqueduct. At the point which, in the interim, will
be that of outfall, and where there will be always

provision for the escape of storm waters, or at Old
Ford Ford Coal-wharf, there will be constructed, on and

adjoining the bed of the river, a pa-ved channel, ex-
tending 30 feet outwards, and about 30 ft. wide.
It will be protected by a permanent dam of guide
piles, sheet piles, and walings, whilst beyond and
in front of it, for about 30 feet, the bed of the river
is to be dredged, and filled in again level with con-
crete and stone pitching. Also a retaining wall
and return walls, with counterforts, are to be con-

strutted ; the former to be 56 feet in extreme length,
15 ft. 9 in. in height, and from 3ft. 9in. to lft. Gin. in
thickness, built with picked " stocks " in Roman
cement, on a piled foundation, and also pro-
tected by sheet piling ; and the return walls to be of
similar construction, extending 15 feet from the
bank, or backwards into the land. Concrete in the
foundations and as backing and " puddle" behind
the wall, will be employed. For these works a
coffer-dam will be required.
From the retaining-wall above described a double
" storm outlet" channel is to be formed for present

use and eventual use, as may be ' required- This
outlet channel is to be 180 feet in length, and in

construction of the work the foundations are

to be got in, the walls brought up, and the arches
turned, to form part of the future outfall-sewer over
the river Lca. At the end of this length of outlet-
channel, the two double lines of sewer, upper and
lower, will commence (we shall follow the line
upstream), and they are to be built in conjunction
with each other for a length of 1,070 feet. In each
of the lower sewers, and abont 670 feet from the
outlet-channel, a tumbling bay is to be formed.
The lines of sewers are to be constructed across and

under the North London Railway, as just men-
tioned. Under the railway, and in a field adjoin-
ing, a double overflow chamber is to be built, 138
feet in length, 70 feet of which at the upper end
is to be 40 feet 6 inches wide ; and within that

space walls are to be brought up at the sides
and in the centre to form weirs, over which the
water will flow and relieve the high and middle
level sewers when overcharged. York-stone
landings, in a double course, with rubbed joints,
set with Portland cement, breaking•joint and made
as nearly water-tight as possible, are to be used for
the floor of the chamber and the bottom of the out-
let-channels. At the end of, and in conjunction,
with, this chamber, three penstock chambers are
to be constructed. A false bottom or floor is to be
formed to two of these chambers, with open iron
gratings, on a level with the inverts of the sewers,
and between which and the floor of the outfall-
channel two flights of steps are to be constructed.
In conjunction with the southernmost penstock-
chamber and high-level sewer, a length of 26 feet
of the middle-level sewer is to be constructed—ter-

minated by a head-wall westward, and haling an
opening to communictte with the high-level sewer,
in which a penstock ivto be fixed. Five cast-iron
penstocks are to be fixed in the overflow chamber ;
two of them 9 feet 6 inches in height by 12 feet in
width, are to be fixed at the junction of the high
and middle-level sewers with the overflow cham-
ber ; and one of the same dimensions in the wall
dividing the two sewers ; and the other two, to be
each 6 feet in height by 12 feet in width, are to be
fixed in the lower chamber. These penstocks are

to be worked by chains and counter-balance weights.
The Wick-lane branch sewer, it appears, will join
the storm outlet sewer, or lower down, near the
river—furnished with a flap and small penstock.