The Sun.
London, England, 1864-07-26 00:00:00

• TILE MAIN DRAINAGE WORKS,

4.

Yesterday what may be termed the annual visit of in-
spection to mark the yearly progress in the execution of
this stupendous undertaking was made by the chairman
and members of the Board of Works, a number of members
of the House of Commons, the Sheriffs, many of the Alder-
men and chief officials of the City, with some of our leading
engineers interested in noting the gradual completion of one
of the greatest, and certainly one of the most important,
engineering works of modern times. Mr Bazalgette, the
engineer to the Board, the gentleman to whose scientific
skill all the plans both for our new main drainage and our
Thames Embankment are due, was, to the regret of all, un-
fortunately prevented by official duties before a Lords' com-
mittee from being present on this occasion. Tho party
numbered between 500 and 600 strong, and wore conveyed
by two steamboats, which started from Hungerford early
in the morning, calling at the various piers down to Wool-
wich for those whose time or business made it more conve-
nient to embark later and lower down the river. The visit
was entirely confined to the northern and southern main
outfall sewers, with their reservoirs, for we are glad to say
the main drainage intercepting sewers are now nearly com-
pleted, and as they extend over the whole of the metrepoli-
tain area, and are 82 miles in length, any other way of in-
specting the works was out of the question.

The whole system of the new intercepting plan of main
drainage may be explained in a very few words. Before
the Board of Works arose our efforts in the way of drainage
were confined to the extremely simple expedient of running
all drains into the Thames; in fact, of making the river
our great main Fewer, and how admirably our efforts suc-
ceeded the smell of the Thames in hot weather soon
showed. Bad, however, as this system of drainage was,
there was one thing even worse, which was the method
of effecting it. The first drains and sewers mado were
in the old districts of the metropolis—that is,
those districts which lay more or less close to the
river on each side, and therefore the lowest in point of ele-
vation of any in the city. It was hard to drain these parts
at all, and it had to be done by taking the sewers so very
much lower that it was only at dead low water they could
empty themselves. As London grew, every year added
enormously to the extent and danger of the evil till
scarcely any sewers could empty but at dead low tide, when
the water in the river was at its minimum, and when the
returning flood swept all the naueous " flotsam and jet-
sam" back into the heart of the metropolis and kept it
churning backwards and forwards for another six hours in
the open air. What effect this at last produced we all
know, though what no knows is why it did not bring a pes-
tilence long ago. It is enough, however, to say that the
evil was so severely felt, and the danger so pressing, that
the " intercepting" scheme of main drainage was at last
adopted, is now, we are glad to say, nearly half executed,
and will before this time twelvemonth be entirely corn •
pleted, with the exception of the small length to be laid in
the Thames Embankment. The intercepting plan, as its
name implies, consisting in cutting three great main drains
on both sides of the river, and which, instead of running
due north and south I;ke the present system, run from west
to east. These great main lines intercept and cut off all the
existing lines of drains from the river, carrying their con-
tents away down to below Barking-creek and Erith
Marshes, where they are poured into gigantic reservoirs
and afterwards, when deodorised, turned into the river at
high tide, and swept away by the ebb almost to sea. Thus,
the sewage is not only turned out free of smell, but turned
out into a body of water nearly 30 times as great as that
into which it used to be poured, and, instead of sickening
the air at our very doors, becomes lost in the volume of
water which rolls down between tha marshes on each side
of the river to far below Gravesend.

On the north side of the Thames, the intercepting
sewers are divided, as we have said, into three distinct
lines, two of which, called respectively the high and
middle level sewers, unite at and pass over the river
Lea ; and the third, the low level, after passing through
the Thames Embankment, will eventually join them at the
proposed pumping station at Abbey Mills. Three parallel
sewers, called the northern outfallrsewer, each 9 feet by 9
feet, are constructed as one work in a concrete embankment,
and are carried by aque.ucts over rivers, roads, and rail-
ways, to the Barking reservoir.
On the south side of the Thames there are three lines of
intercepting sewers, which are also known as the high level,
the middle level, and the low level, and these converge to
one point at Deptford pumping station, where the sewage
from the low level is lifted into the upper level sewers, and
their united stream flows thence deep under Greenwich and
Woolwich, through one outfall sewer, ll►i feet in diameter,
to the Crossness reservoir and pumping station in Erith
Marshes. Three-fourths of London north of the Thames
are, however, elevated so far above the river that the sewage
can be conveyed by its own gravitation to the level of high
water at Barking, and this is why the sewers are carried in
an embankment at such a height above the level of the
marshes, and no pumping station is needed at the outfall.
But on the south side the levels are so low that this cannot
be done, and therefore the outfall sewer is under ground,
and a pumping station is placed at its outlet to raise the
sewage into the reservoir.
The high, middle level, and outfall sewers on both sides
of the Thames are now, with the exception of a few very
minor connections and works, completed. The low level
sewer on the south side will be finished this year, but the
short piece of the northern low level sewer cannot be com-
pleted until the Thames embankment is finished. About
one-third of the metropolitan sewage is nowintercepted and
discharged at the outfalls, and there can be little doubt that
but for this the river would have been much more offensive
this dry season than it has yet been.
The areas drained by the three levels on the north side
are as follows :

Sp.° Miles.
The Northern High Level takes the drainage of
Hackney, Homorton, Stoke Newington, Stam-
ford-hill, Ramsey, Holloway, Kentish-town,
Hampstead, Highgate, and other localities, the
total area of which is
The Middle Level takes the drainage of Bow,
Mile-end, Bethnal-green, Shoredi'ch, Kings-
land, Islington, part of the City, Clerkenwdl,
Holborn, Oxford-street, and from Bayswater to
Kensal-green, and other localities, the total area
of which is
The Low Level takes the drainage of Poplar, Lime-
house, Shadwell, Radcliffe, part of the city of
London, Westminster, Pimlico, Chelsea, Bromp-
ton, Fulham, Hammersmith, and adjoining lo-
calities, the Wal area being

Total 5Ol
The northern outfall reservoir is situated at the point
where Barking-creek fells into the Thames, a little east of
Woolwich, and 11i miles below London-bridge. This im-
mense work was entirely constructed icy Mr Geo. Furness,
under the superintendence of Mr Edmund Cooper, the resi-
dent engineer. The contract price for this great under-
ground hall of waters was £164,050. It covers an area of
about 10 acres, and is capable of containing 6,243,000 cubic
feet, or 39,000,000 gallons. Its depth is about 17 feet, and it
is divided into four compartments. Three of these compart-
ments have already been pled with sewage, but the fourth
was yesterday lighted up for inspection. This was the point
which the visitors inspected first; for none were inclined to
linger on the broad plateau of earth which covers the three
other reservoirs now in use, and from the ventilating
shafts leading into which the most nauseous stench came
pouring out in euch abundance as to make the Tisi-
tors almost fancy they were back on the metro-
politan part of the Thames in summer. They were,
therefore, glad enough to descend into the reservoir which
had not been used, and which was open for inspection and
lighted up. It really presented a wonderful sight. In height
and in the general position of its brick columns and the
spring of its arches it was not unlike the crypt beneath
Guildhall, but the daylight was excluded, and its vast
area was only indicated by little rows of coloured lamps,
which marked the outline of the columns and curve of the
arches, and which, twinkling away in the long, dark,
silent distance till they became minute points of fire and
nothing more, gave to the whole dim interior an aspect
which was at once novel and solemn in the highest degree.
Here and there were little blue points, where the shafts
which communicated with the upper air let in a ghastly
mockery of daylight, but beyond these, which seemed few
and far between, amid the gloom there was nothing but the
coloured lamps and endless vistas of arches, from amid
which voices and echoes of feet' come in a rorlorn murmur.
The Hall of Eblis seemed for once realised in this prosaic
age, or, as the footsteps of the visitors strayed far and wide
into the silence, called up before the imagination the pic-
ture of such a trans-Lethean Vauxhall as Pluto might reign
over. A long time was spent in inspecting this wonderful
interior, the gloomy beauty of which it is difficult to doe
scribe. In a few weeks it will be used as a reservoir, and
can never again be seen with comfort and never again be
entered at all. When the visitors had at last found their
way to the little nebula of fire which the stars and devices
in lamps at the end of the reservoir proved to be, Mr Cooper
got on a platform and answered questions as to the nature
and difficulty of the work, how the foundations often had
to be carried as low as 28ft, how the penstocks or sluicegates
would let the sewage in at one end and out into the river
at the other. Ho explained how culverts had been made
leading far out from the reservoir, almost into the bed of the
river, which could be opened at any time when the deposit
from the sewage became more than six or eight inches deep,
the .reservoir filled and then emptied so as to flush the de-
posited :filth away down the river. The opinions of the
most eminent chemists set little or no value on the much
diluted sewers which finds its way into these reservoirs as
manure. But we should be inclined to think there could bo
no second opinion as to the value of the soft black deposit
which set lea from the sewage, and for which arrangements
have been made to flush it into the Thames. From the
beautifully paved floor of this reservoir it could be collected
with ease by horse sweeping machines, and its value for
agricultural purposes might, one would think, at least be
worth a trial. Before the deep excavations for this reservoir
were made the marches were protected from inundation by
the formation in the river of a coffer-dam, a portion of
which still remains to protect the river bank. There are
16 openings in the side of the outfall sewers through which
the sewage flows into the reservoirs, as regulated by the
penstocks; and underneath them are 16 openings, also re-
gulated by penstocks for the outflow of the sewage into tho
rive: at the time prescribed. The discharge culverts into
the river are visible only at the time of low water—they
are nine in number, and in front of thv-ra is a stone-paved