Construction on the wastewater system began in Cairo Governorate in 1915. At that stage, it was designed to serve 1m inhabitants. In 1936, work started on the system in Giza Governorate to cater for just one quarter of a million people. The limited expansions of these systems, however, has not provided sufficient capacity to deal with the continuously expanding volume of wastewater as the population grows.
The problem reached a peak in the 1960s, when wastewater overflows and flooding affected most of the Cairo areas. The Egyptian government was forced to launch an urgent rescue scheme – the One Hundred Day Project. However, this did not offer a lasting solution to the problem, which continued to worsen with the rapid rise in the population.
In the early 1980s, most parts of the network and pump stations of Greater Cairo, Cairo and Giza Governorates were in a dangerous condition. The government decided to implement a radical solution to the problem in order to maintain public health and to protect the tourist industry, freight utilities and transportation, and to avoid dangers to building foundations and utilities such as telephone, electricity, fresh water and road networks.
A master plan had been prepared and approved in 1978. The major objectives were to:
- Rehabilitate the existing collection system to minimise wastewater flooding
- Build a new collection and transport system to convey sewage away from the city
- Treat wastewater to contemporary standards Maintain proper working levels of all facilities
- Reuse the treated wastewater beneficially
- Use the processed sludge as a soil conditioner
- Generate funding to ensure that the system be self sustaining
The project covers two areas, one on the East Bank of the Nile and the other on the West Bank. This article examines the East Bank project as it forms the major element of the Greater Cairo Wastewater Project. It comprises:
- A network of tunnelled collector sewers from the city centre and adjacent areas to Ameria pumping station
- A major pumping complex at Ameria
- A cross-country conveyance culvert from Ameria to Gabal El-Asfar, including intermediate pumping stations at Kossous and Khalag, and a wastewater treatment plant at Gabal El-Asfar.
The Greater Cairo Project for the East Bank area is based on a large (17 km long) main spine tunnel and 33km of branch tunnels. The design option has been influenced by the density of population, the narrowness of the roads, the location of utilities and the traffic. The main spine tunnel runs from Maadi in the south to Ameria in the north. The main tunnel is 4-5m in diameter and is located 12-25m under the main streets of Cairo. Most of the tunnel route is in soft ground – a mixture of clays, silts, sands and gravel, with a high water table.
The main tunnel ends at Ameria, one of the largest caisson sunk centrifugal pumping stations, extending 32m below ground level. The Ameria Pumping Station culverts, assisted by screw pumping stations, will lift wastewater that arrives this far by gravity into twin box culverts and carry the flows to the Gabal El-Asfar Treatment Plant outside Cairo.
The Ameria Pumping Station is one of the key components of the East Bank scheme and is probably the largest installation of its kind in the world. It houses eight huge centrifugal pumps. The pumping station itself is a vast concrete cylinder 50m high whose base rests 32m below ground level. At this area, the flows from the main spine tunnel and other tunnels converge and will be transported up almost to ground level to take the flow away from Cairo through box culverts 2 and 3, each with openings of 3m x 3m.
Completion of the tunnel connections to the pumping station presented a considerable technical challenge. Ground freezing was chosen to stabilise the varying ground conditions outside the pumping station so that the final sections of tunnel could be excavated safely.
Various branch tunnels join the main tunnel carrying sewage from Central Cairo and its environs. Work on these branch tunnels includes diverting utilities and transport tracks and associated installations; altering the arrangement of public streets; and other miscellaneous work to establish working sites. The main works include construction of various lengths of 2500mm diameter tunnel, 1800mm and 1200mm nominal diameters bolted segmental, precast concrete lined sewer tunnel, as well as transition and connection tunnels.
A number of access shafts and drop shafts of 6000mm, 5400mm and 4850mm nominal diameter will be constructed using in situ-concrete or bolted segmental precast concrete linings. The tunnels and shafts will be finished in blue brick.
The East Bank project has been divided up into 19 contracts (17 of them construction contracts).
Project status
Contracts 1-9, 12, 12/A, 15 and 17 are now in service, and Contract 16 priority works and streams A + B of the wastewater plant are finished. For Contract 14, comprising the Boulac Branch Tunnels, five tunnel shafts have been completed and 560m of microtunnel have been driven. Four hundred metres of tunnel lining have also been carried out. The expected completion date is March 2000.
Works for Contract 15 are now substantially completed.
At Gabal El Asfar, the flow reception chamber, culvert, inlet pumping station and by-pass channel have been operating for 21 months. The flow has again been averaging 1 million cm/d. Stream A and B, Wastewater Plant is operating, with a flow of 500 000 cmd being treated. Initial steps in commissioning streams C&D screens and grit removal system have been successfully completed. Tank remedial is essentially complete, but some pipe cleaning and testing is still outstanding. In the STF area, pipework is sufficiently finished for road works and landscaping to resume in C and D areas. Work is progressing towards introducing sludge in late summer 1999.
Related Files
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