A pilot project is proving viable for countering the decades of neglect that have left Lahores sewers blocked and flooding. But solving the problem city-wide is likely to need both private sector involvement, and better rubbish collection, according to the findings of a scheme being carried out with support from the UKs Department for International Development.
Lahores trunk sewer network, which serves the citys population of between five and seven million, discharges directly to the river. It has had little maintenance in the 60 years since it
was installed. Sewers are heavily silted up, with 48 diameter runs often blocked to half their depth. Blockages are traditionally solved by the simple expedient of pumping the flows into surface drains, or nullahs, really intended for monsoon flows. The sewers then get left alone. Mobile pumps become semi-permanent pumping stations, says DFID engineering adviser Peregrine Swann.
There is extreme flooding during the monsoon because of these blocked sewers, adds DFID engineering field manager Philip Barlow, and there is a lot of political pressure to alleviate it.
An added problem is that sewers in Lahore are used for rubbish disposal, explains David Whiles, a director of Carl Bro International which is DFIDs consultant on the scheme. Unless the solid waste problem is addressed, they may need cleaning again in five to 10 years, he warns. DFID is trying to encourage co-ordination between the local authorities to improve rubbish collection, and has also set up a local self-help scheme.
The Department has committed some 19M to the Lahore water and sewerage project since 1988, with 2M spent on the sewer cleaning consultancies, equipment and a pilot project.
The cleaning project came out of a twinning consultancy started in the late 1980s between the citys Water & Sanitation Agency and the UKs North West Water International and Binnie & Partners. This involved a review of the whole of WASAs operations, while other major components included the design and construction of sewage pumping stations by Balfour Maunsell, and utilities mapping by Carl Bro. One of the problems being highlighted by the mapping project was that the sewers were extensively blocked, says Swann. Adds Whiles: We could identify where the tops of the manholes were, but we couldnt then link the pipes together.
Sewer cleaning equipment had been supplied but trunk sewers werent being cleaned, says Swann. Hence the need for a pilot scheme.
Carl Bro International was commissioned in 1986 to set up a project implementation unit within WASA. This unit is now a sewer cleaning directorate, comprising WASA and consultants. Carl Bro project manager Peter Rowley leads the firms team there and the unit includes local firm Progressive Consultants.
There are three main thrusts behind Carl Bros work, explains Whiles: demonstrating that cleaning can be done by the private sector, training locals to work safely in sewers, and developing a rolling programme to clean up the citys network over the next five to 10 years.
The pilot scheme involves cleaning 4.5km of trunk sewer in the densely populated medieval walled area of the city below the fort. This sewer only accounts for about 5% of the network but serves 20% of the population.
Silt is loosened by high pressure water jets while a suction device lifts the resultant sludge to the surface. Operations can be carried out from the surface or by people in the sewers.
Large vacuum units from UK firm Brain Associates can suck solids through 10m or so, pulling out cobbles and even bricks. This is the first time this type of project has been carried out anywhere, says Whiles. It could prove a model for other cities in the region. The equipment was adapted specially from other uses such as mining.
While the equipment was being manufactured, some manual cleaning contracts were let and WASA is not at all convinced that mechanical means are better than manual, says Swann. There is no shortage of manpower, though only one group of the community, the Christians, will carry out this work. However, the smaller 600mm sewers could not be cleaned manually.
Sewers that have been cleaned are suffering considerably less blockages, and there are calls for the work to be extended, with support both politically and from WASAs managing director Mian Mohammed Amin.
While DFID pays for consultancies and equipment on the project, the World Banks Punjab urban development project has paid for the contractors. World Bank financial support is drawing to a close and the likely way for WASA to continue is through private sector concessions. We are looking to fund a consultancy to take the project forward to awarding a concession, adds Swann.