The Sun.
London, England, 1857-10-15 00:00:00

.31STROPOLITAN BOARD OF WORKS.

MAIN DRAINAGE OF THE METROPOLIS.

A meeting of the Board was held yesterday in
he Council chamber, Guildhall, to further consider
he communication received from the First Corn-
eissioner of her Majesty's Works, &c., in relation
o the main drainage of the metropolis ; Mr.
Chwaites in the chair.
After some explanations on certain engineering
points had 'been given by Mr. Bazalgette, the en-
gineer of the Board,—
Mr. CARPMAEL rose to move that the reports of
he board submitted to the Commissioner of her
Majesty's works and public buildings, also the re-
)ort of Messrs. Galton, Simpson, and Blackwell,
us referred to two eminent engineers, and the en-
gineer of the board to report thereon at their ear-
liest convenience. The chief commissioner had re-
amed the plan B* submitted to him by the board
tcoompanied with a report which. had been pre-
pared under his direction by three eminent engi-
leers, and he had invited the board to well con-
sider that report. It would appear from that re-
port that those eminent gentl?raen by whom it was
prepared were of opinion that the board had not
arrived at a wise and proper conclusion on the sub-
;ed. But in order to ascertain the value of the
propositions of those civil engineers it was desirable
see first wherein those gentlemen differed from
the board. They started with stating that they
themselves had based their plans upon the same
principle as that adopted by the engineer of the
• board ; and theyfurther stated that no other prin-
ciple could with propriety be used in carrying out
this great work. The board therefore was justified
so far as the principle of their plan was con-
cerned. Subject to certain suggestions and modi-
fications, they likewi-e approved other portions of
the plan propounded by the board ; especially
that of having a high-1e vel sewer on the north
and south sides of the Thairnes. They agree as to
the expediency of a low'-level sewer on the
southern, but they differ as to the propriety of
having a low-level sewer on the north side of the
Thames. They also agree to the want of two middle-
ievel sewers, but they propose to have these con-
structed so as to get the benefit of a larger area,
end to carry the sewage into tht) Thames by the
simple act of gravitation. They propose to carry
the sewage across the Thames at Battersea, there to
be raised by artificial means into a southern high-
level sewer, so as to arrive at the Thames by gravi-
tation. In these several respects the Board and the
referees were largely agreed. It must not there-
fore be supposed that because Sir B. Hall had sent
back the plan B* he disagreed with it in toto, be-
cause his own engineers did not do that. He
believed that the plan of the Board had come back
from the First Oommissioner stamped with a deg-ee
of credit that no engineering plan of like dimen-
sions had ever before received. It had not only met
with the approval to a great extent of those three
eminent referees themselves, but it had also the
support of Mr. Foster, Sir W. Cubitt, and Mr.
Stephenson, who were formerly Commissioners of
Sewers, as far as regarded the principle upon which
that plan was based. Was the board then prepared
at once to accept the engineering propositions of
Messrs. Galion, Simpson, and Blackwell ? He did
not believe that any man would do so. But, if not,
was the Beard prepared, on the other hand, to take
the responsibility upon them of rejecting those pro-
pmitions without making any engineering inquiry ?
He thought not. The First Commissioner had re-
quested the Board to take the report of the Go-
vernment referees into consideration, not because
he himself approved their suggestions—for in regard
to them he had expressed no opinion—but because
it was, as he believed, the wish of that right hon.
gentleman to have se great a national work exe-
cuted in the best possible manner. All the proposi-
tions of the referees depended upon the possibility
of their having one outfall sewer, 18 miles long,
with a fall of six inches a mile. If they could not
carry out that portion of their plan, then all those
parts of it which had reference to a larger area, for
the purpose of conveying the sewage by gravita-
tion and to a larger rainfall, must fall to the
ground. It was, therefore, to that point—
namely, the practicability of such an outfall sewer
—that he invited the attention of the Board.
Tho proposition was this the formation on
either side of the Thames of an open cutting which
they called the main outfall channels. Etch of Vies°
channels was to be 16 feet deep and 38 feet wide,
with a general fall of 6 inches in a mile. This would
be able to carry away an enormous amount of sew-
age and rainfall. The report of the referee., though
exceedingly voluminous on matters of information
which anybody might have collected, was very mea-
gre when it came to practical facts. It was not
known whether those three eminent engineers pro-.
posed to have gates at the end of their outfall chan-
nels or not. They stated that the cuttings would
commence near Barking on the north side, and near
Woolwich on the south side. The top of the chan-
nel on the Woolwich side would be level with
Trinity high-water mark, and the top of the north
side cutting would be 6 inches above Trinity high-
water mark. It was said that these cuttings would
extend to Sea Reach with a fall of 6 inches a mile ;
but, strange to say, when they came within four
miles of Sea Reach, the fall was at the rate only of
1 foot 6 inches per mile. The consequence of this
would be that from 10 to 13 feet of water would be
col s tan tly lying at the bottom of the sewer, and be
washed up and down with the tide for a distance of
12 miles. These channels would, moreover, be
tide-locked, for there were inverts 284 feet on one
side of the river and 29i on the other side below
Trinity high-water. As shown by their own diagrams
and sections, the low-water mark was from 10 to 13
feet above the inverts. The consequence would
be that the sewers would never empty themselves.
But then these gentlemen proposed, in order to in-
crease the current, to take water in from the river
at high water and from the reservoirs to be
constructed at the upper end into their outfall
channels. First, then, it was proposed by them
to take water into the reservoirs and then to let the
water in the reservoirs run intothe channels. But
the report was silent altogether as to the depth of
these reservoirs. The engineer of the Board had

here detected a great fallacy on which these gentle-
men had founded their scheme. The whole ques-
tion rested upon this,—what were to be the size and
depth of the reservoirs 2 At present the top of the
outfall channel on one side was on a level with
Trinity highwater mark, and on the other side six
inches above that mark. Now, the spring tides at
Woolwich were coincident with Trinity high-water
mark. It was quite clear, therefore, that they
could not take in any water at high-water mark
—that was to say, at spring tides. The neap
tides were sometimes lower than Trinity high-
water mark, and sometimes as much as five feet
higher. When lower than high water mark the
depth of the outfall sewer must be considerably
reduced. But the whole fallacy of the plan was
fancying that it was possible for them to get an al-
titude at Woolwich with a constant higher head of
water than they had in the river here, from which
they had to derive it. It was quite clear, in an
engineering point of view, that if they had an al-
titude affording a high head of water they would
always drive out every particle of sewage from the
open channels. But, as they were dependent upon
the Thames for obtaining that altitude, they could
only only get it as the Thames could bring it to
thorn and the Thames could not bting them a
constant head of high water under any circum-
stances whatever. Supposing the reservoirs were
deep enough! to keep up an altitude of heed
water at spring tidee, and supposing that
they had no gates at the outfalls, the tide
would rise to the same height in the
ontfall sewers as it did in the Thames ; and the
sewage would flow just as freely in the Thames as
in the outfall channels ; there would be no head
water in favour of those cuttings. But, although
he was himself convinced by these reasonings, yet
he did not expect the board to adopt his conclu-
sions without inquiry. Ho could not ask them to
come to a resolution that the scheme propounded
by the Government referees was based on a fallacy.
He could only ask them to call in furthe: profes-
sional aid, who would investigate the scheme and
• report whether the engineers who hid propounded
it were right or whether what he had been stet ng
wee correct. The plans of the board had been re-
ccmamended to them by their own engineer, for
whose skill and
1
judgment he euterta:ned the highest
respect, and he (51.
• C arpmael) having himself in-
vestigated those plans, he hid arrive d at the con-
viction that Mr. BazalgetatenAicKseasvd more practi-
cal knowledge in details,
to
tter acquaint- d
with principles having„ referenwcas
this particular
qr. estion, than any other man 11:wor (Cheers.)
He was delighted to hear that a copy plan
h of
the engineer of this board had been-
seclinttihtberyett
eenr:l-
- of the Government to all the
Deers for their opinion as to its eilleacy in rt,f,renlcie-
to their particular districts, and that out of the 40
gentlemen, all men of talent, who constituted that
body, not one had objected to the broad principle
of the plan. (Hear.) Seven of the number hi 1 of
gi /ell any answer to the circular ; six had suggested
certain alterations in details for the convenience of
their particular districts ; and 26 of those gentle-
m to had entirely accepted the plan, saying that, in
their opinion, it was amply sufficient to carry out
the great work of the board. He would ask them
whether it was not the fact that their plan had
come back to them with a degree of credit and of
stability with which no plan of any former engi-
neer had ever bees honoured. Under these circum-
stances he submitted that the only proper course for
the board to take was, since their plan had been re-
turned, together with s. report,from the 3 engineers
to whom its consideration had been referred by Sira