The Sun.
London, England, 1856-04-04 00:00:00

METROPOLITAN BOARD OF WORKS.

(This Day.)

The weekly meeting of this board was held this after-
noon at the Council Chambers, Guildhall; Mr. Thwaites,
in the chair.

DRAINAGE OF THE DISTRICTS SOUTH OF THE THAMES.

The principal subject brought before the board was
the report of the engineer, Mr. Bazelgette, relating to
the drainage of the districts south of the Thames, which
was read and afterwards ordered to be printed for the
information of the board, and its consideration was ac-
cordingly adjourned.

- -
The following is the elaborate report of the engineer
on Via important subject :
" Greek-street, Soho, 3d April, 1356.
" Mr. Chairman and Gentlemen—ln carrying out the
foregoing instructions, my attention has been directed first
to that portion of the metropolis which lies upon the south
side of the river, where improved drainage is most ur
gently required. The Board will probably remember that
in 12•53, pursuant to directions by the then Metropolitan
Commissioners of Sewers, designs for intercepting sewer,
on the south side of the river were prepared by me. The
plan now submitted for your cousileration will be found to
resemble, in its main fe Acres, the former scheme ; it
ttieref9re becomes necessary to recapitulate several of the
lea liug considerations referred to in my report of 1853, and
in the joint report by Mr. Haywood and myself upon th.
northern drainage in 1851, whilst I have at the same time
endeavoured to take advantage of all the information
gained in the subsequent preparation of the northern
drainage scheme, and to profit by the experience of the
last three years. The modifications now introduced will,
I trust, be regarded by you as improvements.
" In 1849 tha Commissioners of Sewers publicly invited
plans and suggestions for the main drainage of the metro-
polis, and their invitation was warmly responded to by
many who were interested in the subject. 116 plans were
sent in ; all of which I, in conjunction with Mr. Cresy,
examined and classified, and they were reported on by a
committee of the Commissioners of Sewers, consisting of
Sir J. F. Burgoyne, Captain Vetch, Jas. M. Hendel, Esq.,
Captain H. 1). Harness, and Robert Stephenson, Fsq.,
whose report was printed and laid before Parliament.
other plan sand suggestions subsequently received'
were considered and printed by the Commissioners of
Sewers.
" The late Commission expressed their unwillingness to
receive further plans and suggestions, and about 27 were
sent in and are now before this Board.o They have been
arranged and classified, and a summary of thorn is ap-
pended to this report (see Appendix A), whilst it is diffi-
cult to select any one of them as deserving your exclusive at-
tention, wavy of them bear marks of great thought and
labour, and 1 acknowledge with pleasure that most of them
contain some useful information or hint.

" Almost every suggestion which can be made upon the
subject has been now so often repeated in some shape or
other, that it would be difficult to determine who were the
first authors of the various schemes and theories pro-
pounded. Having had the advantage of access to all, 1
cannot pretend to much originality, my endeavour has
be-n practically to apply suggestions, originating in a large
measure with others, to the peculiar wants and features of
the different districts, with which my position has made
fumii tr. _

" Before entering into the details of the plan of drainage
now proposed, it may be well briefly to consider what are
the natural features awl requirements of the district to be
dealt with, and what the objects sought to be gained.
" Half of the southern area extends along the south bank
of the Thames, and the surface of the ground is generally
below high water in the river, varying from its level, to
six feet below it.
" This tract is by nature a marsh, which has been re-
claimed from the river by artificial embankments, and is
now closely built over, and thickly inhabited, forming a
large and important portion of the metropolis. Many of
the houses have basements and cellars below the surface,
and the sewers which are beneath them are necessarily so
low that they can only discharge their contents into the
river for about four hours each tide. The sewers being
close.' at their outlets for the remaining eight hours, be-
come reservoirs of stagnant sewage for 16 hours in every
day, and unavoidably accumulate deposit. To maintain a
continual and unintermitting flow in the sewers of this
low district and to drain the cellars and subsoil effectually
so as to make thorn dry and healthy, demands the aid of
pumping. The effe'se, of which has been described by Sir
Cubitt and Mr. Stephenson in their report of the
17th Oct., 1833, as being tantamount to raising the level
of the district 0 feet, producing in its sewers a continu-
e Ils and P.m discharge, and entirely overcoming the natu-
ral disadvantages of its situation.
" The remaining portion of the South Metropolitan area
is at present thinly covered with buildings, which are,
however, rapidly-increasing as the suburbs of the Metre-
polls extend. The surface of the ground rises gradu-
ally from the level of the low district to an extreme ele-
vation of about3so feet, and the rain %vett rs which full upon
the high district descend with groat rapidity into the
sewers of the low district, which being tide-locked, as
already described, and of insufficient capacity to store a
large and sudden influx of storm waters, during high
water in the river, become overcharged, and in such cases
the sewage floods and destroys much valuable property.
The suddenness and destructiveness of these inundations
increases in proportion to the progress of building and
drainage iu the upper district. To remedy the evil arising
from this cause, it is proposed to intercept the waters of
the upper district, so as to prevent their descending into
the low district, by forming a hi ghlevel or, catchwater sewer,
with a free outlet and a constant discharge by gravitae
Lion. The risk and expense attending the process of pump-
ing a large body of water pouring down suddenly at
iriegular intervals, where any interruptions in the process
would be productive of great inconvenience and loss, ren-
ders it, in my opinion, expedient to get rid of all the up-
land waters in the manner proposed, by a high level or
cistchwater sewer, instead of allowing them to add to the
difficulties, sufficiently formidable in themselves, arising
from the waters falling upon the low district
"In the plan now proposed, the objects sought to be
attained- are twofold and distinct,-Ist, to provide
proved outfalls for the drainage of the entire area, and 2d,
by a system of interception to relieve the Thames from the
po lotion to which it is now subjected. Some of the sewers
proposed are designed to serve the double purpose of drain-
ing and interception, whilst others are simply "Intercept-
ing Sewers," anti do not, of themselves, drain the district
through which they pass, but merely supply artificial
eh:mares by which the sewage is diverted from the drain-
age sewers, and carried away to a new and less objection-
able point of discharge into the river.
" With regard to the point of discharge; I cannot do
better than quote from the report of Mr. Stephenson and
Sir William Cubitt, dated the 11th December, 185 r,
wherein they give the following brief summary of a eerie,
of experiments made by the late Mr. Frank Forster upou
the subject.
" Oa the 15th of July, 1831, a float was put into the
centre of the river, opposite learkiug Creek, two h airs
after high water. This time was chosen because it wee
found that sewage discharged into the liver two hours
before high water, arrived at shout the same point above
Barking Creek that sewage discharged two hours after
high water did by the next flood tide. At low water it
reached Ili miles below that point, and returned with
the next flood tide to one mile above it, having gone 121
miles that flood, it being then the period of spring tiles.
" As the neaps came on the float continued to wink
lower down each succeeding high water, and by the 21th
of July it was 13 miles below Barking Creek at high
water, having gone down the river 14 miles during tie
falling off of spring tides to neap tides: As the flood again
became stronger, it worked up the river each succeeding
tide until the 29th of July, when it again became within
five miles below Barking Creek at high water, having
worked up the river 9 miles from high water neap tidos to
high water spring tides, the excess of the ebbs over the
floods being only 5 miles in 14 days.
" Another experiment was tried at the same place on
the Gth of August, 1851, it being then lowest neaps, and
the float being put down two bouts after high water. It
worked up each succeeding high water till top springs on
the 12th of August, when it reached 6e miles above Bark-
ing Creek at high water. Thu float then again worked
down the river till the 20th of August, being neaps when
at high water, it reached 91 wiles below Barking Creek,
being a distance of 16 miles, during the feliiug off or spring
tides to neap tidos. The excess of the ebbs overthe floods
would, in this case, have been about 7 wiles in 14 days.
The wind and other causes would vary the result ; but it
may be roughly assumed that a substance in suspension
works up the river about one mile a day each high water
as the springs strengthen, and down the river two miles
a day as they fall off.
" ' The main object was, of course, to determine how
near to London the sewage could be discharged into the
river at or near high water, without finding its way beck
again to the inhabited parts of the town. The experiments
proved that it was essential to go as far as Barking Creek,
and also as regards the level of discharge, they demon-
strated that it should take place at or near high water as
practicable.'
" Now, although it is desirable to fix the place of dis-
charge as far below the metropolis as possible, it will be
found that a practical limit to it is imposed by the neces-
sity of maintaining sufficient fall iu the sewers to keep
theta clean, and at the seine time of preserving as a safety
valve a discharge into the river at low water by gravitation,
in case of accident to the pumps, as well as during exces-
sive floods. It must be borne in mind 'that the delivery
of the sewage at high water into the river at any point, is
equivalent to its discharge at low water at a point 12 miles
lower down the liver • therefore the construction of 12
miles of sewer is saved by discharging the sewage at high
instead of at low water.'
"The position selected is Plumstead-marshes, and the
period of dischrrging the sewage into the river would be
from two to four hours nearest to high water.
" The amount of sewage proposed to be intercepted from
the more closely inhabited districts has been estimated
upon data, which makes provision fur the increase of future
generations.
" Thus, where the population, as at present existing.
exceeds 30,000 to the square mile, the actual numbers are
estimated for ; and where it is less allowance has been
made for that number, in order to provide for future in-
crease. The supply of water per head has been reckoned
at five cubic feet per diem, being on a more liberal scale
than now actually obtained; and of this qu. ntity it is
contemplated that one-half will pass away during six home
of the day.
" For reasons more fully set forth in former report, it
is proposed, in the urban districts, to intercept a quarter
of an inch of rain in 24 hours, which is at the rate of
about 100th part of an inch per hour ; any excess beyond
that amount, falling oa occasions of heavy storms, being
discharged into the river by the drainage sewers.
" With a view to economy by the reduction of the sizes
of the sewers, as far as practicable, it is now propreted to
continue the drainage of all those portions of the subtitles
which are net likely to be belt upon for many years to
come, into their natural valley outfalls; and where build-
ing has already commenced, and is likely to be extended,
to provide for an increase of population varying from
10,000 to 20,000 to the square wile instead of 30,00 )• Tt
is further proposed, from the more thinly-peopled suburbs,
to carry off by the intercepting sewers only one-half of
the quantity of rain water f)c which provision is made in
the more crowded districts.
" The 'different areas drained, and the quantities pro-
posed to be intercepted, are stated in detail in a table ap-
pended to this report. (See appendix B.)
"The sizes of sowers, their inclinations, and their dis-
charging powers, under various conditions, are important
considerations in forming a drainage scheme. In the pre-
sent instance it is a matter of moment to economise the
fall so as to reduce the amount of pumping, and, as
far as practicable, t preserve safety outlets
into the river, and in order thereto to adopt
the minimum velocity sufficient to keep 'the sewer a free
from deposit ; the velocity depending upon the fall in. the
sewers of a &ail size.' .Upon this eioiritiMre Wicketead in
his report upon the drainage of Leicester (p. 19), states,
From experiments made by me with great oare, I Said

that with a bottom velocity of 16 inches per second only
(or 0.0 miles per hour), heavy pieces of brick, stone, &c.,
will be removed, and that with a velocity of 21i inches
(or 1.24 miles per hour), even iron borings and heavy slag
will be removed. The above minimum velocity will there-
tore be sufficient.' Mr. Beardmore, in his work on Hy-
draulics, states (r. 8) that A. velocity of 153 feet per
minute (or 14 miles per hour), will generally prevent de-
posit in pipes and sewers.' Mr. John Phillips states (see
irst report of Sanitary Commission, 1817, p. 177),
From observation and experiment, I find that it requires
a constant velocity of current to be running through the
~ewers, equal to about feet per second, or 14 miles per
h mr, to prevent the soil from depositing within them.'
"Professor Robinson, in his ' Theory of Rivers,' states,
•it page 465, that " we learn from observation that a ve-
lecity of three inches per second at the bottom will just
begin to work upon fine clay for pottery, and, however
irne and compact it may be, it will turn it up. . . .
A. velocity of six inches will lift fine sand ; eight inches
mill lift sand as coarse as linseed ; 12 inches will sweep,
Tong fine gravel ; 24 inches will roll along rounded pebbles
oi inch in diameter, and it requires three feet per second
.t the bottom to sweep along shivery angular stones of the
size of an egg.'
"Mr. Stephenson and Mr. Hawkesley consider a velocity
of two miles per hour ample where there is a continual
stream, and these opinions are further confirmed by the
,xperience of Mr. Haywood and myself.
With reference to the fall requisite to produce this
velocity, the calculations universally adopted by hydrau-
!ic experimenters and engineers, and upon which my esti-
tastes are based, show that in a sewer Oft. Gin, in dia-
meter with a fall of 2 feet per mile, the mean velocity
vould he about 2 miles per hour when running three
quarters full, or 1.88 miles per hour when running half
roll, and about 1 2.31 miles per hour when running one-
third full.
" But the velocity of a stream is governed by the di-
mensions of its channel, as well as by its rate of fall. Thee,
in a sewer 10 feet in diameter with a fall of 2 feet 'eer
mile, there will be the same mean velocity of stream when
running half full, as in a sewer 2 feet in diameter with a
fall of 10 feet per mile.
" Where ecoeolny of fall is required, it is desireable, so
far as other considerations will permit, to graduate the
leclivity of the sewers so as to produce an uniform rate
of flow in them, and thus to avoid a waste of fall in one
portion of the design, and an insufficient velocity in an-
other.
" When the proper velocity and the practicable limits
which can be assigeed to the fall are ascertained, it is easy
to determine the size of the sewer requisite to carry off a
constant and defined quantity of sewage in a given time.
"On the other hand, when in dealing with drainage
outfalls, we have to provide for rains variable in amount
and duration, and where absorption, evaporation,
►nd the time occupied by the waters in flowing
from the points on which they fall, over various
surfaces and levels to the point of discharge have
to be taken into account, the question is more com-
plicated, and it is under such conditions that we are in-
d:kited to Mr. Hawkesley's formulae, with respect to which
Nfr. Stephenson and Sir William Cubitt in their report of
the 11th December, 1854, stated that, 'No part of engi-
neering science has been more industriously investigated
than the laws that govern the flow of water in pipes and
open channels; and it is probably not too much to say,
that the formulae which represent these laws rank amongst
the most truthful that the professional man possesses.
They have been the subject of laborious experimental in-
vestigation of the most elaborate character, and their re-
sults have been tested by the practical under every variety
of conditions, without their truth being impugned in
the slightest degree. The principles upon which they
are founded have been sanctioned and adopted by Prong,
Eytelivein, Du Beat, and others; and it is to them that
we are indebted, in a great measure, for the simple practi-
cal form which they present. Our own engineers have
modified them to suit particular circumstances, and given
them more extensive usefulness. Mr. Hawkesley, amongst
others, has especially contributed to render the principles
which they embrace applicable to almost every variety of
condition which the complete drainage of largo towns in-
volves, and we shall have occasion, almost immediately,
to adduce some instances within the meta opolis, where the
facts confirm theoretical deductions in a very remarkable
manner, and lead irresistibly to the conclusion that they
may be implicitly depended on.'
"The sizes of the sewers required at the various points
of interception are given in the tables and sections ap-
pended to this report. A circular form has been adopted
in this preliminary design, i❑ order to facilitate the pre-
paration of the estimates, and calculations of discharging
power ; but it is proposed to execute them of a slightly
eliptical form, which is preferable in point of strength,
and the alteration will have no appreciable effect upon the
estimates or design.
" Having thus briefly touched upon several of the more
leading general principles which govern the design, we
now proceed to the consideration of the works proposed.

" THE HIGH LEVEL SEWER.
"The high level sewer is designed to act in the double
capacity of a drainage and an intercepting sewer; it will
ultimately divert the sewage and a portion of the rainfall
due to 14 square miles 518 acres of the upper district from
the low district, conveying them away by gravitation to
the level of low water in Plumstead Marshes ; the storm
waters alone beiag suffered to descend into Deptford Creek.
Its route varies but little from that of the high level sewer
designed in 1853. It commences at Clapham-common, at
such a level, and with such a capacity as will enable it at
some future time to be extended to Tooting and to Batter-
sea-rise. Passing along the High-street, and through
Stockwell-green, it intercepts the Effra Sewer at the junc-
tion of the Brixton and Loughborough-roads, and con-
tinues through fields and garden ground, and along Cold
aarbour lane to Pligh-street, C tmberwell, where
it intercepts the Earl Sewer. Thence its course is
along Love-walk and fields to the Victoria-road, Peckham.
At this point it receives the Effra branch, and thence con-
tinues eastward, through private ground between the New
Cross-read and Nunhead Cemetery, intercepting the Peck-
ham, and Peckham-rye branches •f the Earl sewer in its
route ; and passing underneath the Brighton and North
Kent Railways at New Cross stations. Thence it proceeds
under the Ravensbourne and along the Greenwich-road
into the Woolwich extension line near to Deptford Pump-
ing station.
It discharges its storm waters, during heavy rains, by
an overflow into Deptford Creek ; the effect of which will
be on mach occasions to flush away the mud and refuse
now collected in the creek, and to deepen and improve its
channel.
" Eton) Deptford Creek the united streams of the high
an i low level sewers flow through the extension sewer,
by gravitation along the Trafalgar-road, and the Green-
wich and Woolwich lower road to Woolwich. Thence
under Albion-road, Gearge-street, Church-street, the
churchyard and private property to Powis-street, across
Beresford square, and along the Plumstead-road ; round
the south-oast corner of the Arsenal, and in a direct
line across Plunastead-wirshes to a point opposite to
Barking Creek, its level there being th it of low water at
spring tides. The total length of this lino of newer from
Clapham to its outfall will be about 11 miles 4,170 feet.

" HIGH LEVEL BitANCH.

f` This branch commences by a junction with the Effra
Ipen sewer at Croxted-lane, near Dulwich, and joins the
main level in the Lyndhurst-road, Peckham, being about
two miles 565 feet in length. It affords a deep outfall for
Dulwich, which is now lly drained and subjected to
floods, and it saves the covering of a considerable portion
of the Effra sewer, which takes a more circuitous and less
advantageous route.
" THE LOW LEVEL SEWER.

" By the low level sewer provision is made for the inter-
,!option of the sewage from a district which may eveetually
be extended over 22 square miles. This sewer commences
at the High-street, Putney, passes along Wandsworth-
lane, through, Wandsworth, and under the Wendt°, into
the York-road, through Battersea-fields, along Priory-
road, Lansdowne-road, the Clapham-road, and Holland-
street to the Brixton-road, intercepting in its course
all the main sewers near the river Thames, and being
provided with penstocks and storm overflows, by moans of
which the currents in these sewers will be placed under,
command.
At the junction of the Brixton and Vassall reads the
Effra will bo again intercepted, and its present defective
condition in this locality remedied. The lower portion of
the Effra will then he reconstructed of a much snial;er size
than at present, with a fall from the river to the low level
•
sewer, to which it will act as a storm overflow.
"At the junction of the Camberwell and Albany roads
the Earl sewer will be intercepted. From thence the main
lino proceeds along the north side of, and under the Grand
Surrey Canal, to the Old Kent-road, where the Peckham
branch of the Earl sewer is intercepted. Thence the low
level sewer proceeds in a direct line across the fields and
market gardens, under the Brighton and North K, nt Rail-,
ways, to the junction of Giffen-street with High-street,
Deptford. Here it receives the north branch, and is pro-
vided with an overflow into the river at, low water. It
then proceeds between the gas and vitriol works, near the
Greenwich Railway, under Deptford Creek, to the pump-
ing station on the banks of the Creek. The total length
of this line, from Putney to Deptford, is about 9 miles
2,550 feet.

" LOW TOWEL OR BERMONDSEY BRANCH.
"This branch commences at St. James's Church, Rother-
hithe, at which point it forms a coniection with, and sup-
plies an outfall to, the Battle-bridge, the Earl, the Great
Saint John, and the Duffield Sewers, and thus completes
the interception of the sewage from the low district. It
passes through private ground into and along the Dept-
ford Lower Road, under the Grand Surrey Canal, along
Evelyn street and High-street, Deptford, where it dis-
charges into the main sewer.
" DEPTEORD PUMPING STATION.
"The position selected for the pumping station is a
piece of waste land on the east bank of Deptford Creek,
south of the Greenwich Railway, and neat the Gas and
Vitriol Works, at which point the sewage from the low
level sewer is raised to the high level.
• "The invert of the low level sewer will here be about
204 feet below that of the high level and the extension
sea ere, and about 30 ' feet below Trinity high water mark..
Pumps and engines equal to 520 nominal horse power will
be required, and it is proposed to provide duplicate engines
in cases of accident an i repairs. There will be no reser-
voirs, and the engines and pumps will be covered so that
the sewage will not be exposed, and no inconveniences will
arise therefrom.
" RESERVJIR AND ENGINES AT PLUMSTEAD MARSHES.
"In order, finally, to discharge the sewage into the centre
and bottom of the river within from two to four hours
nearest to high water only, it is proposed to °oust ruot upon
the banks of the river a covered reservoir capble of con-
taing 4,000,000 cubic feet of sewage, to be raised into it
from the main outfall sewer. The land required for the
reservoir. engine-houses, pumps, &c., would be about 15
acres. The lift being about 21 feet, 657 nominal horse-
p pro-
ower will be reuired to raise the sewag and it is
posed here to prqovide duplicate engines e,
as at Deptford
Creek.

ENGINE POWER.
" The total amount of engine power to be provided will
be about 2,354 nominal horse-power, and the annual cost
of pumping will probably amount to 12,000/ on the
cost aver-
age, or about one-third more than the present of
cleansing the tide locked district sewers.
" The effect produced by the Deptford Pumping Station
upon these sewers, would be so beneficial as largely to re.
dues the present annual cost of cleansing them, and thus
to diminish this increased.annual expenditure.
"The estimated cost of tho works herein recommended
will be as follows:

" ESTIMATE•

High level level sewer, from Clapham to Deptford, and
510
Branch. ..................... . 2115959,
'
Extension from Deptford to Plumstead
Low Level Sewer from Putney to Deptford, and
Branch ........ . ................... .. ............. . 209,000
Reservoir and Land for Purowng Stations
Engine-houses, Engines, PUMPS,/Sze 161,780

Total
1,696
..
" Having given the design now submitted to you my
best consideration, I present this report under a deep sense
of the gigantio magnitude and importance of the eubjeot,