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Egypt has already spent more than Pounds sterling 500 million to keep
sewage off the streets of Cairo. But that is not enough to do the job properly.
As the United Nations water decade draws to a close, Egypt is struggling
to find the extra cash it needs to keep its capital safe and clean.

ONCE AGAIN Egypt is the site of a major water engineering project. As
far back as the 19th century BC, the pharaoh Senusert III cut the first
canal linking the Mediterranean Sea to the Red Sea via branches of the Nile
delta; 37 centuries later, de Lesseps built the Suez canal. This time the
project is in, under and around the capital itself: construction firms are
revamping and expanding the network of sewers, pumping stations and treatment
works that make up the ‘Greater Cairo Wastewater Project’. With contracts
worth Pounds sterling 500 million already under way, and another Pounds
sterling 200 million necessary to complete the first phase of the work,
engineers believe the project is the biggest and most challenging waste
water scheme being built.

Istanbul is also the site of a major cleanup, but this work is not on
the same scale as that going on in Egypt. Cairo is twice the size of Istanbul,
and its system is more heavily overloaded. The first phase of the Cairo
project will increase the capacity of the system to cope with waste water
expected from the beginning of the 1990s; the second phase is planned to
make the network ready for the next century. The Cairo project is costing
more to complete, not least because of the more expensive engineering methods
necessary to tunnel sewers deep underground. Whereas Turkish engineering
contractors can drill and blast their way through rock, their counterparts
in Egypt are having to chew through waterlogged silt.

An overhaul of Cairo’s existing system is complete, and new sewers,
tunnels, and pumping stations should be ready to use, after some delays,
by 1991; but contractors have not started work yet on new treatment works
to make the sewage safe. And if contracts to expand the system further are
not let soon, Cairo’s growing population will overload the new network as
soon as it opens. The problem is that the Egyptian government has been having
trouble borrowing the extra money it needs to realise its ambitions.

The project is not only meant to dispose of the city’s sewage more efficiently
but, by taking the effluent off the streets, to improve the health of the
citizens. This is in line with the United Nations’ plea in 1980 for investment
in water supply and sanitation throughout the developing world. The UN’s
water decade draws to a close this year but Egypt’s problems will last well
into the next decade at least, as the city continues to grow.

Egypt is crowded and hungry. Less than 4 per cent of the land is cultivated,
just 4000 square kilometres, which must support more than 50 million people.
And so is Cairo, which now ranks as the largest city in the Middle East
and Africa. A high birth rate, a steady flow of villagers from the countryside
to the capital, and most recently, refugees from Sinai and Gaza fleeing
war with Israel means Cairo is bursting with more than 12 million citizens.
This crowding puts a heavy strain on the city’s infrastructure. Cairo’s
system dates from a time when the population was only a third of what it
is now. Investment in the system has fallen way behind the growth in population
and in the demand for water. The wars helped to swallow up cash that was
badly needed for maintaining, and expanding, the crumbling infrastructure.

By the 1970s untreated sewage was regularly flooding many areas of the
city with its flat, low-lying streets. Even today, after 10 years of reconstruction,
the city treats less than half of the 2 million cubic metres of sewage that
enter its system every day. Waste that can be adequately treated irrigates
agricultural land: the rest, along with the untreated sewage, flows into
open drains that empty into the Nile or into a lake on Egypt’s Mediterranean
coast.

This is not all the sewage that Cairo produces, however, for the system
does not serve around three million citizens. They live in the squalid suburbs
where housing is unplanned, or in the old mudbrick villages that the growing
city has engulfed. Their sewage accumulates in cesspits or is thrown into
canals that other people use as a supply of water for washing, cleaning,
cooking and drinking. Also, leaks from weak or fractured sewers threaten
to contaminate the mains water supply from the Nile.

In Cairo the big killers are not tropical diseases such as leprosy or
sleeping sickness, but ailments such as gastroenteritis that poor sanitation
encourages. In 1986, UNICEF estimated that 131 children in 1000 born in
Egypt died before the age of five: the main cause is diarrhoea. This is
10 times the rate in developed countries. The city has all the ingredients
for an epidemic of cholera or typhoid, and the risks can only increase.

In 1977, with funds from its rich Arab friends, the Egyptian government
began to devise a strategy for revamping Cairo’s waste water system. In
12 months it drew up a grand plan for the city with the help of John Taylor
and Sons and Binnie and Partners, two engineering firms from Britain, and
prepared to do detailed design. Then President Sadat launched his peace
initiatives towards Israel, and the Arab world swiftly withdrew its support.
Egypt turned to the West. The US and Britain came up with some cash – not
as much as was needed but enough to get started – and Taylor and Binnie
joined two American firms, Black and Veatch and Camp Dresser and McKee,
in a consortium known as the American British Consultants, or Ambric. The
consortium’s task was to design a scheme that would bring modern waste water
technology to all of Cairo.

The first job was to overhaul the existing system. For instance, Ambric
found that a type of arteriosclerosis restricted sewage flow through the
network and reduced the capacity of the system substantially. Many of the
sewers were clogged with grit from the dusty, unpaved streets. For although
it rains little in Cairo, the rain falls in heavy showers that turn the
streets into trails of viscous gritty mud. This flows into the system. During
the first year of the renovation programme, which began in 1980, teams of
labourers cleared drains of around 43 000 cubic metres of grit, rags, low-grade
fuel oil and untreated industrial waste. They used semi-automatic buckets
and, in obstinate cases, high-pressure water jets to shift muck from 57
kilometres of sewers. Renovation lasted six years before Ambric could make
a start on increasing the capacity of Cairo’s waste water system.

On the east bank of the river European and Eygptian contractors are
doing the work, while on the other bank American firms dominate activities.
Egypt is footing most of the bill; Britain has donated more than Pounds
sterling 50 million and it has underwritten commercial loans of Pounds sterling
185 million, while the US has given about $400 million. The British and
American governments have provided this money on condition that Egypt spends
it on British and American expertise and equipment. The Egyptian government
has committed about Pounds sterling 150 million to the project.

The older, and more heavily populated, east bank of the city sprawls
out below Saladin’s 11th-century citadel. Here Ambric decided to improve
the system with a deep tunnel, or main collector, stretching the length
of the city, which would enable sewage to flush through the existing network
more quickly. The idea was sound; the problem was how to dig the new tunnel.
When contractors start to build a new town or development, they lay sewers
simply by digging down into the ground from the surface: this is tricky
when a city is already in place. Cairo, in particular, full of narrow streets
and very densely populated, leaves little room for contractors to dig up
the streets. Also, plans of buildings are out of date and the tangle of
pipes and cables below the surface is poorly mapped.

There is another problem. Cairo is built on saturated alluvial mud with
the water table about 3 metres below the surface. Digging through this old
river deposit is like trying to make a hole in sand at the seaside: when
you get to water the hole starts to cave in.

The only way engineers could install new sewers in Cairo was to do the
job entirely underground, sometimes working in tunnels full of compressed
air, to stop the soft walls collapsing, and at other times, in firm rock,
blasting their way through with explosives. From the limestone under Cairo’s
southern suburbs through the soft mud below the city centre, contractors
dug the 17-kilometre tunnel to a new pumping station at Ameria on the northern
edge of the city. Tunnelling is now complete and construction teams are
busy lining the bore with protective bricks to resist chemical attack.

At Ameria, engineers are building the large pumping station to push
the sewage of about four million people, which can top 25 cubic metres a
second, into culverts just below ground level. The waste will then flow
15 kilometres to a spot beyond the edge of the city where the government
is planning to build a new treatment plant; subsidiary stations along the
way, with Archimedean screw pumps, will help it to flow down the shallow
gradient of the delta. Until the new plant is ready – and at the end of
last month the government had still not secured finance for the project
– the culverts will simply discharge their untreated sewage into agricultural
drains.

On the other side of the Nile, in the fertile plain at the foot of the
5000-year-old pyramids of Giza, American contractors face similar construction
problems. But unlike their counterparts on the east bank, they must build
a new system from scratch as well as improve what exists already. The new
system is for the large, crowded slums that have appeared not far from the
spacious, tree-lined avenues of the wealthy Cairenes who were attracted
across the river in the 1930s.

Removing sewage from the city centre is only half the story, however;
subsequent treatment is essential to make it harmless. There are three main
stages in converting toxic sewage to harmless sludge and water: during preliminary
treatment, screens remove grit and rags; during primary treatment in sedimentation
tanks, heavier solids settle out; and during secondary treatment, pumps
force air through the remaining sewage to encourage bacteria to decompose
its organic content. Further sedimentation and chemical treatment may follow.
If this is not done before the effluent reaches a river, for instance, continuing
bacterial action in the decomposing organic matter starves other forms of
life of oxygen, and the water becomes putrid. This is what is happening
in the two agricultural drains that carry effluent away from Cairo. Waste
from the west bank empties into the Muheit drain, which joins the Nile about
25 kilometres downstream of Cairo. Sewage from the east bank discharges
into the Bilbeis drain, which flows into the semi-salty, or brackish, Lake
Manzala near Egypt’s Mediterranean coast. Cairo has five treatment plants
but together they remove less than one third of the pollutants in the city’s
sewage. American engineering contractors are rehabilitating the plant at
Zenein on the west bank: the other four are due to be scrapped.

It will be some years before Cairo’s sewage is disposed of safely. Untreated
and partially treated sewage will continue to drain into the River Nile
and Lake Manzala until new plants at Gabal el Asfar on the east bank and
at Abu Rawash on the west bank are ready to use. These two plants, plus
new branch tunnels, are expected to cost around Pounds sterling 200 million.
But construction on neither one has started yet and when it does it will
last at least three years. The Egyptian government is still looking for
the Pounds sterling 100 million or so that it needs to build the first stage
of the plant at Gabal el Asfar. As a last resort it has asked the companies
keen to do the work to find the money.

The shortage of funds, and the delays it is causing, have become critical
issues. For instance, culverts carrying effluent to the proposed treatment
plant at Gabal el Asfar are designed to cope with flows up to the year 1990,
and yet they will not be complete until well into that year. Even then they
will not carry any sewage until engineers build, at the very least, basic
works at Gabal el Asfar. Meanwhile work on phase two of the project, which
is designed to expand the system to cope with estimated flows in the year
2010, has got no further than the drawing board. It is not the only ambition
that lack of finance has frustrated. The original grand plan for Cairo,
completed in 1977, estimated that water from treated effluent could be irrigating
400 square kilometres of reclaimed desert by the year 2000. Treated sludge
is also valuable as a fertiliser and soil conditioner. In a land as crowded
and hungry as Egypt, being unable to use that water, and the fertile sludge
it carries, is like pouring money down the drain.

* * *

Cairo’s antiquity squeezes engineers of ingenuity

CAIRO sits in the Nile valley at the foot of limestone cliffs from which
the ancient Egyptians excavated stones for the great pyramids of Giza. Limestone
is a good construction material but it underlies only the southern suburbs
of Cairo. Most of the city sits on a layer of silt or clay several metres
thick, above beds of medium to coarse sands.

Increasing the capacity of the waste water system called for a tunnel
about 5 metres in diameter to be excavated under the city. Tunnellers used
drilling rigs and explosives to drive through some limestone rock in the
south, while circular shields with clusters of rotating teeth, or cutting
heads, chewed their way through the softer material below the city.

In this saturated silt engineers had to find ways of stopping water
and sand flooding the tunnel. Along one stretch they pumped in compressed
air at a pressure of up to 2 atmospheres to seal the tunnel; elsewhere they
sealed only the ‘face’ of the tunnel they were driving. This they did by
pumping a slurry into the gap between the shield and the face: excavated
material fell into the slurry, which was pumped to the surface through a
network of pipes, cleaned and recirculated. As the circular cutting shields
crept forward, construction teams fitted segments of precast concrete around
the inside surface of the bore to support and to line the tunnel.

Tunnelling is now complete, and engineers are busy protecting it against
future chemical attack. In the stiflingly hot summer months when temperatures
regularly top 40 Degree C, bacteria work swiftly on the sewage. When oxygen
is present, they generate sulphuric acid, which eats away at tunnel linings.

As far back as 1918, engineers noticed severe corrosion in the main
sewers of the original system. The only reason the sewers did not suffer
more damage was because they were overloaded and full most of the time;
with little oxygen in the sewers the bacteria gave off more hydrogen sulphide
than sulphuric acid, and corrosion slowed down.

To protect the new tunnel, engineers are lining the top three-quarters
of the collectors with blue bricks made from Aswan clay, whose partial vitrification
makes them resistant to acid attack.

At Ameria at the northern end of the tunnel, which is about 22 metres
underground after dropping gradually so that sewage will flow under gravity,
engineers are building a pumping station. This giant underground cylinder
of concrete, 31 metres deep and 44.5 metres in diameter, will house eight
pumps. Each pump will be capable of lifting 3600 litres of sewage through
24 metres every second. The station, which is costing Pounds sterling 30
million to build, will service around four million people.

Building the Ameria pumping station has required considerable ingenuity.
The problem, as with the tunnel, was how to dig a large, deep hole in waterlogged
silt. Artificially lowering the water table was out of the question since
the dense housing nearby could have subsided, along with the pumping station
still operating on the site, and it could have caused fractures of old sewers.
Engineers considered freezing the ground and cutting out the soil as a block
of ice, but in the end they decided that this would have been too expensive
and taken too long. They also thought about excavating the hole in compressed
air to stop the walls collapsing, as they had done for sections of the tunnel.
But the hole was so big that the large reserves of air necessary to cope
with leaks or failures in pressure made the idea unrealistic.

In the event engineers chose a technique that has been popular in Cairo
for more than 20 years, the ‘wet caisson’ method, though it has never been
used before on such a large scale. The plan was to build the future underground
walls of the cylindrical station above ground and then let them sink into
place under their own weight. As construction teams built up the concrete
walls on the back of a circular steel cutting edge, 44.5 metres in diameter,
the tube began to sink into the soft silt: dredging pumps sucking sludge
from the centre of the caisson helped the cylinder to descend. Engineers
expected the 30 000-tonne caisson to glide through the silt in six months.
Halfway down, however, the heavy concrete tube started to tilt: the caisson
seemed to be locked into the mud on one side. Extra loading on top of the
caisson did not help and the project stalled. Engineers only managed to
smooth the caisson’s passage into place by creating an artificial slip plane
in the form of a 600-millimetre trench around the outer edge of the cylinder.
Into the trench they pumped bentonite, a naturally occurring clay that engineers
often use as a lubricant, or as support for equipment they are using, in
difficult ground. The job still took five times as long as expected to finish:
the caisson finally reached its destination late last year.

When the new system is complete, the eight pumps will lift sewage from
the main collector to large culverts at ground level, which will guide it
under gravity to the edge of the desert.

* * *

The legacy of hand-to-mouth survival

UNTIL the beginning of this century the waste water system of Cairo
was only a few kilometres of open drains lined with masonry. In 1907, J.
Carkeet James, a British engineer, designed the first sewerage system to
cope with the city’s needs until 1932, when the population was expected
to reach 960 000. He built a system on the east bank to dispose of 48 000
cubic metres of waste water a day, about 2 per cent of the current rate.
Sewage flowed to one of 63 ‘ejector’ stations, which pumped the waste out
of the city. Pressurised air, fed around the city through a network of pipes
radiating from a central compressor, powered these stations. Between 1910
and 1915, James installed a main collector, more than 250 kilometres of
street sewers and 9500 house connections, as well as a treatment plant.
Sludge from the plant fertilised farmland developed with the scheme. But
in 1927 a census showed that the population had already topped one million,
and another main collector was built. A third was added to the system in
1950.

By then the spacious west bank had become a fashionable area to live.
In the mid-1930s, the area received its first sewerage system, along with
Cairo’s first secondary treatment plant at Abu Rawash on the edge of the
desert. But new construction lagged far behind population growth. The system
became overloaded and sewage frequently flooded onto the streets. In 1962
the situation was so serious that the government responded with an unprecedented
flurry of activity. Over three months it built drains, pumping stations
and two plants for the primary treatment of sewage. The hectic salvage operation
became known as the ‘100 day’ scheme. But by then the system on the east
bank had become so overloaded that the government authorised the construction
of a tunnel under the Nile to line the two networks. The tunnel housed two
inverted siphons, both 1.2 metres in diameter, which sucked sewage from
the east bank to the west bank for treatment. This increased the flow in
the new system, which was already heavily overloaded.

In 1970, the government built a fifth plant to treat waste water at
Zenein on the west bank. It too, however, was overloaded almost from the
day it opened, and like much of the system suffered from a lack of funds
for replacement parts, expansion and maintenance.

One incident, however, has helped to maintain the momentum of the present
programme of rehabilitation. In December 1982, a steel main laid during
the 100-day scheme burst in Giza on the west bank, flooding housing and
making residents furious. Only 17 days of concerted efforts quelled the
chaos. By then, local and foreign press as well as President Mubarak had
visited the scene. Unpleasant as it was the incident brought publicity to
the new project and underlined its importance.

James Bedding is a freelance journalist who writes about the Middle
East. He recently returned from Cairo where he contracted hepatitis A.