Restoration of sewerage systems : proceedings of an international conference

312 Pages·1982·116.353 MB·English

* f
RESTORATION OF SEWERAGE SYSTEMS
Proceedings of an International Conference organized by the Institution of
Civil Engineers, held in London on 22-24 June 1981
THOMAS TELFORD LTD, LONDON, 1982
Published for the Institution of Civil Engineers by Thomas Telford Ltd, PO Box 101, 26-34 Old Street, London EC1 P 1JH
First published 1982
Conference entitled 'Maintenance, repair, renovation and renewal of sewerage systems' sponsored by the Institution of Civil Engineers
Organizing Committee: J. E. V. Holmes, D. F. Rees, J. N. Rushbrooke and W. B. Varley
ISBN: 0 7277 0145 2
© The Institution of Civil Engineers, 1982, unless otherwise stated
All rights, including translation, reserved. Except for fair copying, no part of this publication may be reproduced, stored in a retrieval
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The Institution of Civil Engineers does not accept responsibility for the statements made or for the opinions expressed in the following
pages
Printed and bound in Great Britain by the Burlington Press (Cambridge) Ltd, Foxton, Cambridge
Contents
Opening address. The Rt Hon. TOM KING, MP 1
THE UK SITUATION
1. The assessment of the problem in the UK. E. C. REED 3
2. The sewer dereliction problem-evidence from collapse studies. N. CULLEN 9
Discussion 17
THE WORLDWIDE SITUATION
3. The international scene. R. S. DARLING and J. DRAKE 21
4. Investigations of sewer failure in Denmark. E. B. ANDERSEN 29
5. A method of sewer rehabilitation-the Toronto experience. R. M. BREMNER 37
6. Status of sanitary and combined sewer systems in the USA R. H. SULLIVAN and
W. F. FOSTER 45
7. Replacement of existing sewers in Calcutta streets. A K. CHATTERJEE 53
8. Sewerage in Sweden. J. ADAMSSON, O. NISTE, P. BALMER and H. BACKMAN 59
Discussion 69
THE IMPACT OF SEWER FAILURE ON THE PUBLIC, INCLUDING OVERALL
COSTS
9. Petersham Road, Richmond, sewer failure. L A PROBERT, J. E. V. HOLMES and 77
K. J. FLEMONS
10. Ground movements caused by deep trench construction, I. F. SYMONS, B. CHARD
and D. R. CARDER 87
11. Ground movement and pipe strain associated with trench excavation.
P. B. RUMSEY, I. COOPER and K. KYROU 105
Discussion 117
THE SEWER INSPECTION-CONDITION SURVEYS, CLASSIFICATION
12. Corrosion problems in sewerage structures. P. H. PERKINS 133
13. Monitoring for management M. H. WHEATON 141
14. Surveying Severn-Trenf s sewers. R. BALMER and K. G. MEERS 149
Discussion 157
SEWER RECORDS AND MONITORING FLOWS
15. Experience in the use of a computer program to simulate sewer networks under
surcharge. P. J. COLYER and R. K. PRICE 163
16. Sewers and water mains-a standard record system. P. W. STYLES and H. M. H EDDERLY 169
17. Infiltration: investigation, analysis and cost/benefit of remedial action. C. MARTIN,
D. KING, N.J. QUICK and N. A NIOTT 175
18. Practical aspects of computerised sewer records. D. J. BRACE 187
19. The role of flow surveys in the hydraulic analysis of sewerage systems. M. GREEN 193
Discussion 201
PLANNED MAINTENANCE, ASSESSMENT OF PRIORITIES, PREDICTION OF
SEWER LIFE AND DETERMINATION OF THE OPTIMUM LEVELS WITH SEWER
REPLACEMENT OR RENEWALS
20. The assessment of the structural strength of brick sewers. J. L DAKERS, P. H. BOND,
N. D. ECKFORD and A. G. SINKINSON 205
21. Renewal of sewerage pipelines in the Lake Mj0sa area, Norway. S. SAEGROV 213
22. Longitudinally cracked pipes and their structural capacity. J. J. TROTT, P. NATH and
M. P. O'REILLY 221
23. The development of a sewer policy for sewer rehabilitation. D. C PETERS 235
Discussion 241
HEALTH AND SAFETY-TRAINING EQUIPMENT AND SAFE SYSTEMS OF WORK-
TRADE EFFLUENT CONTROL
24. Health and safety-safe systems of work: an appreciation of potential hazards to
Staff. A D. CALTHORPE 245
25. Some aspects of health and safety matters in sewerage systems in the UK.
I. H. BURNETT 251
Discussion 257
TECHNIQUES AND METHODS FOR RENOVATION AND RECONSTRUCTION
26. A city's experience of thin-shell sewer lining. I. MUNRO and M. J. HOLMES 259
27. Sewer dereliction and renovation—an industrial city's view. G. F. READ 267
28. Making use of the hole—new techniques for sewer renovation. G. C. COX 283
Discussion 289
Closing address. P. F. STOTT 303
Index 306
Opening address
The Rt Hon. Tom King, MP, Minister for Local Government and Environment Services
1. During the past decade or so, experience both 4. We must then tackle the problems exposed by
in the UK and abroad has shown that we can no the survey. Have we the materials and methods
longer take our sewers for granted. In the to ensure that the most cost-effective, long-
north-west of England we have had visible proof lasting solutions can be adopted? Should we
of perhaps the worst effects of age and struc­ revise our specification for new construction
tural decay. The problems of Manchester's cent­ work? We must concentrate on systems which
ral area have been well publicized - I have will have low maintenance and energy require­
seen some of the more serious collapse incidents ments in the future.
there for myself. There is certainly a great
5. The most important aspect of the problem is
deal of work to be done in that area.
its cost and how it can be financed. At present
2. In other parts of the country the indicators the UK spends about £100 million annually on
are less clear. We have in the South the replacing and repairing sewers. Is this enough
example of the Petersham Road collapse which to cope with the rate of deterioration? What
proved so expensive to repair, and more recent can we afford? It is clear that in present
research is beginning to show that conditions circumstances we are not going to have enough
approaching those in Manchester may be exposed money to enable everyone to carry out all the
in one or two other regions such as Yorkshire work they feel is necessary in their own areas.
and central Scotland, but how much do we really How are we to meet this problem? As a first
know about the extent and scale of the problem? step the Government has introduced current cost
It has been estimated that the replacement accounting to the water authorities' budgets.
value of all this country's sewers is £40 000 This will help to focus people's minds on the
million. This is a staggering sum. How much real cost of maintenance of the service. There
of the system is already in need of replacement, are other methods; in Toronto, Canada, for
over what period should we be planning a renewal example, a connection charge is made for all new
programme, and of what size? buildings to help fund the capital programme.
3. There are serious difficulties in finding the 6. There are three urgent needs: to gather the
answers to these questions. A lot of our sewer necessary information about the scale and
records are incomplete or do not exist at all. priority of the problems; to improve and perfect
Many sewers were constructed 100-150 years ago cost-effective construction and renovation
and may be in poor structural condition as well techniques, and to plan a rational long-term
as of unknown size and situation. This is the programme of investment within the UK's avail­
first of the challenges to be met. We must able resources which will meet its priority
establish the extent and condition of our sewer needs. This Conference offers an opportunity
system, by survey and development of inspection to start off this logical process in the right
techniques which will identify defects. Some way.
of the equipment needed is already available
and new devices are being developed.

The assessment of the problem in the UK
E. C. REED, OBE, DFC, FICE, FIMunE, FIWES, FBIM, MIWPC, Thames Water Authority
The author reviews the growth of sewers from the early nineteenth century and makes an assessment
of what is now in use in the United Kingdom. He goes on to describe the problem now facing the
water industry and what has been achieved in finding a solution. He stresses that it is essential
to exploit our greatest asset - the hole in the ground.
"As one who long in populous city pent, where houses thick and sewers annoy the air. " MILTON (1608-74)
HISTORICAL BACKGROUND
1. The United Kingdom, with a figure of 9h% proved Snow's theories.
connected, enjoys the benefit of the highest
proportion of households on mains drainage in 6. The following notice which appeared in The
the world. The beginnings of this drainage Times newspaper in I8U9 perhaps paints the
system was the direct result of the Industrial backcloth to this history of sewerage for it is
Revolution which caused a large proportion of the incredible poverty and suffering of the
the population to shift from the countryside working classes that demanded recognition and
into the towns and cities. swifter change.
2. In the early part of the eighteenth century "A SANITARY REMONSTRANCE
town drainage consisted of open ditches which
flowed into the existing streams or rivers. We print the following remonstrance just as it
The enormous increase in the number of houses has reached us, and trust its publication will
that were built and in the amount of paved assist the unfortunate remonstrants:-
area that was laid created a vast increase in
the runoff of surface water. This in turn THE EDITUR OF THE TIMES PAPER
caused the already full drainage ditches to
overflow exacerbating a health hazard that was Sur, - May we beg and beseach your protekshion
to become the curse of the Industrial Revolution. and power, We are Sur, as it may be, livin in
a Willderniss, so far as the rest of London
3. The water supply, although preceding sewer­ knows anything of us, or as the rich and great
age, was rudimentary in its distribution and people care about. We live in muck and filthe.
stretched available resources to the limit to We aint got no priviz, no dust bins, no drains,
the extent that pumped water was only available no water-splies, and no drain or suor in the
two or three times a week. hole place. The Suer Company, in Greek St,
Soho Square, all great, rich and power fool men,
k. The habits of the population, the use of take not notice watsomedever, of our cumplaints.
midden heaps and privys adjacent to water The Stenche of a Gulley-hole is disgustin. We
supplies, was largely responsible for the spread all of us suffur, and numbers are ill, and if
of water borne diseases such as cholera although the Colera comes Lord help us.
this fact was of course not known at the time.
Dr. John Snow, whose name is now immortalised by Some gentlemans corned yesterday, and we thought
a London public house in Broad Street, first they was comishoners from the Suer Company, but
applied what is now known as epidemiology and they was complaining of the noosance and stenche
correlated the cases of a violent cholera out­ our lanes and corts was to them in New Oxforde
break with the use of a particular water pump. Street. They was much surprised to see the
In ten days in 185^ 500 people died in an area seller in No 12, Carrier St, in our lane, where
bounded by three streets and these people all a child was dyin from fever, and would not
drew their water from one well. beleave that sixty persons sleep in it every
night. This here seller you couldent swing a
5. As a result of Snowfs deductions the pump cat in, and the rent is five shilling a week;
was closed and eventually it was discovered that but there are greate many sich deare sellers.
sewage was seeping into the well that supplied Sur, we hope you will let us have our cumplaints
the pump. It was not until 30 years later that put into your hinfluenshall paper, and make
Robert Cork isolated the cholera virus and these landlords of our houses and these comish-
oners (the friends we spore of the landlords) 10. We are indeed fortunate that the Victorians
make our houses decent for Christians to live in, did everything on a grand scale for we are still
living off the fat that the early enthusiastic
Preaye Sir oome and 'see us^ for we are living drainage engineers provided. It is, however,
like piggs* and it aint faire we should be so unfortunate that we have not treated these buried
ill treated. assets with the respect that they deserve for
there is little doubt that some of our sewers
We are your respeakfull servents in Church Lane, are in a serious structural condition. But
Carrier Sty and the other corts. how many and how serious? - that is the question.
Teusday, Juley Z 1849" ASSESSING THE PROBLEM
3
1. In 1975 the recently formed National Water
7. At this time sewers were already in exis­ Council jointly with .the DoE set up eight
tence but had been built to relieve flooding standing technical committees to cover all
and up to the year 1815 it "was illegal to drain aspects of the water cycle. One of these,
sewage into them. However, sanitation problems Sewers and Water Mains, gave an opportunity for
became so great that the Authorities accepted known engineering experience to be applied to a
the practice but it was I8U7 before the law was national problem.
changed and it then became compulsory to drain
houses into the sewer. 2. Four major difficulties became immediately
obvious,
8. We probably owe the birth of our sewerage
system in the UK to a major cholera epidemic in - lack of knowledge
1831 which caused a Royal Commission to be set - lack of records
up the following year. Edwin Chadwick was one - known ageing
of the District Commissioners appointed and it - no use of failure records.
was he who produced the famous report on the
sanitary condition of the labouring population 3. The first step was to publicise the problem
in I8U2. The data collected over five years and the National Assessment was published. This
makes sobering reading but it is the recommend­ has since proved to be the forerunner of a whole
ations that are of interest to us today and host of articles and papers, many of which have
they included the establishment of drainage relied on that original document for their data.
systems and the concept of soundly designed That data was not easy to obtain and it was with
sewers with self cleansing velocities. some difficulty that it was established that the
total length of public sewers in the UK was in
9. Development followed rapidly and some men the order' of 23*+,000 kms. made up from the
were inspired to innovate. Such a man was regional water authorities sub-totals as shown
Joseph Bazalgette for it was he who was faced in Table 1.
with solving the problem of TThe Great Stink1
in 1858. Sewers, which had been laid to convey h. If sewers are considered to fall into two
storm water ran directly to the river so that size categories, man-entry and non man-entry,
the waste of the Metropolis converted the Thames only 5% of the system in the UK are of man-entry
into an open sewer. Bazalgette constructed size. The remaining 95% consist of 25% which
interceptor sewers on both sides of the river are between 300mm and 1 m. and 70% 300mm dia­
picking up all of the main outfalls and conveyed meter or less. This assumes that 1 m. diameter
the flows downstream to Barking and Crossness. is of man-entry size, an assumption which is
In a 15 year period from 1859 some 100 miles of debatable.
large trunk sewers still is use today, were
constructed. 5. We know that some of our sewers are well
Population Sewer Pipe density Population per
Population (P) Area served (A) density (P/A) lengths (L) (L/A) sewer length (P/L)
Authority 000's km2 persons/km2 km km/km2 persons/km Remarks
North West 7 000 14 489 483 30 578 2.110 228
Northumbrian 2 680 9 753 274 10 850 1.112 247
Severn Trent 8110 21 630 374 38 463 1.778 210
Yorkshire 4 672 13 648 342 16 093 1.179 290
Anglian 5 400 27 000 200 23 013 0.852 234 (i), (ii)
Thames 11 588 12 926 901 50 694 3.922 230
Southern 3 766 10 932 344 13 840 1.266 272
Wessex 2 200 9 867 222 8 800 0.892 250
South West 1 350 11 217 120 5 230 0.466 258
Welsh 2 986 19 800 146 11 372 0.574 255
Total England and Wales 49 852 151 262 329 208 733 1.380 238
Scotland 5 226 78 774 66 19 573 0.248 267
Northern Ireland 1 547 14 120 110 5 972 0.423 259
Total United Kingdom 56 625 244 156 231 234 278 0.960 241
UUUKKK fffiiiggguuurrreeesss CCCeeennntttrrraaalll
(i) 5600 km2 on main drainage
SSStttaaatttiiissstttiiicccaaalll OOOffffffiiiccceee 555555 999666888 222444444 000111333 222222999
(ii) 3,700,000 population served by main drainage
Table 1. Sewer distribution by length, United Kingdom totals
over 100 years old but we know little of the age filtration, tree root intrusion, rat infestation,
distribution or the growth rate for the system. and open joints.
A number of theories have been propounded based,
for example, on population shift and house 3. It is not possible in the space and time
building and both of these give some guidance. available, or indeed with our present knowledge,
An example of the problem is shown in Figure 1 to try to fully associate these faults either
which gives details of some typical sewers still with each other or the factors that contribute
in service in Manchester. to them. Nevertheless, some explanation is
essential because it provides some of the back­
6. The value of our underground sewerage as.sets ground for the papers which follow.
updated from Ql 1975 to Ql 198l prices has been
estimated as Zk2 000 million and although the Fabric Corrosion and Erosion
accuracy of this figure may be suspect, it is, h. A large percentage of sewers are constructed
as was stated in the foreword of the National from clay based products. Whilst these pipes
Assessment, the best estimate that can be are highly resistant to erosion and chemical
derived from the present available data. attack, the cementitious jointing materials,
which have been commonly employed in sewer con­
7. The exactness of the figure is not important, struction, suffer badly in these respects.
but the following message from the foreword of Deterioration of cement and lime mortar in brick
the National Assessment is still very valid sewers not only causes direct structural weaken­
today. ing, but also permits infiltration of groundwater
which may cause further deterioration. Similar
"The reader will see that two messages problems exist with pipe sewers causing pipe
come out of the report loud and clear; settlement and joint displacement. The only
the first is that the quality of in­ erosion problem commonly encountered, is at the
formation available about these buried invert of soft brick sewers subject to high
assets varies tremendously across the velocity flows. Aggressive industrial chemicals,
country, the second is that whichever both acidic or alkaline, may corrode the
way it is looked at, current expendi­ materials used in sewerage systems and there can
ture on sewer and mains maintenance be weakening of fabric attributed to molecular
does not appear to be keeping pace with changes as opposed to removal of fabric via
the inevitable deterioration taking corrosion or erosion. The formation of hydrogen
place." sulphide can result from slack gradients or in
sewage pumping mains and is particularly aggress­
8. There is no doubt that the problems that we ive to cementitious materials. Of the relatively
are currently faced with stem from lack of proper small quantity of sewers constructed of materials
maintenance over several decades. It appears other than clay, it is the concrete and cast iron
that too little money has been reinvested in a pipes that appear most vulnerable to corrosion.
valuable asset although it must be appreciated
that if a reasonably accurate depreciation rate Age Weakening of Fabric
is not established it is impossible to calculate 5. Clayware sewers do not age weaken appreciably
what this annual expenditure should be. unless subjected to shattering by thermal stresses
or severe acid attack. This also applies to
9. Apart from the lack of basic record data concrete and cast-iron sewers if corrosion and
already mentioned we do not know the structural erosion are not involved. The only pipes which
life or the rate of deterioration, parameters are believed to suffer true age-weakening are
which are absolutely crucial for the establish­ those composed of plastics, pitch fibre and
ment of a strategy to overcome a backlog of glass-reinforced cement.
neglect. This strategy unfortunately must be
developed in a climate of economic decline when Backfill/Bedding Disturbance
our available resources are being stretched 16. Backfill/bedding may be disturbed by the
almost to the limit. There is therefore little infiltration of groundwater into the sewers or
room for manoeuvre and we must make every penny by adjacent workings. In general a brick sewer
count. will suffer more severely from the disturbance
of backfill/bedding, for in its absence it will
WHAT CONSTITUTES THE PROBLEMS tend to collapse under its own weight.
1. Our sewerage system spans some 150 years but
age is not necessarily the only criterion by Increased Loading
which to judge condition. There are numerous 17. Sewer deterioration may accelerate as a
factors which are contributory to the present result of alteration of depth of cover or
poor state of the reticulation. These include changes in surface use (e.g. highway improve­
depth, geology, height of the water table, pipe ments, increased traffic usage).
specification, influent, quality of workmanship,
adjacent services and traffic loading. Cleansing Practice
18. There is substantial evidence to prove that
2. These factors sometimes individually, although the use of inappropriate cleansing techniques
more often in combination, manifest themselves in has accelerated sewer deterioration.
a range of faults which include cracks, fractures,
collapses, blockages, deformation, displaced Tree Roots
joints, erosion, corrosion, infiltration, exfil- 19. The smallest crack or open joint is sufficient