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Riddle of the sands

ENGINEERING WATER Water transfer

Although beset by drought, Iran is set to export water to Kuwait.

Alan Sparks explains the paradox.

Near Defzul, in western Iran, the recently constructed Karkheh Dam holds back some 5,600M.m3 of water.

Elsewhere in Iran the land is blighted by prolonged drought - but Karkheh can offer no immediate relief.

The riddle is explained by Gulf Utilities director Brian Hendry:

'The topography of the terrain between the drought affected areas and the Karkheh Dam make a pipeline unfeasible at this point. Water provision to these areas will be better met by financing other schemes through the royalties earned from exporting water by an easier route.'

So a £2.4bn, 540km long steel pipeline will carry 50M litres of water south to Kuwait every day 3per second. Hendry explains, 'Although this is a big scheme it will be merely complimentary to desalination. There's no question that Kuwait will ever be dependent on Iran and this pipeline for its water.'

The Karkheh Dam was principally built to provide 400MW of electricity and regularise water flow to the irrigated farmland downstream. Such large scale projects are nothing new to Iran.

'There's a lot of work being done over there with large dams, infrastructure and pipelines of around 100-200km in length, ' says Gulf Utilities director Colin Clark.

Only 0.6% of the Karkheh river's flow into the Gulf will be taken through the Kuwait pipeline which initially collects its regular flow downstream of the dam. A 2.74m diameter steel pipe will travel southward 330km overland, basically following the main road to allow easier access.

Practically every ground condition imaginable will be encountered along the planned route with rock, dunes, clay, sand and an estuary-like area, presenting an added corrosion issue.

A service road will run along the length of the 25mm thick, 600m head pressurised pipe, providing ease of access for maintenance. Although the overland pipeline will be almost entirely buried, four major river crossings will need to be negotiated by pipe bridges.

'Once the diameter of a pipe exceeds about 1.2m, steel really comes into its own, ' says engineer Binnie & Partners (Overseas) director John Grimes. 'It's cheaper, stronger, lighter, easier to repair and when you're dealing with a pressure head of 600m, the welded joints perform far better than any concrete locking system.'

A 170,000m 3reservoir will be built at the initial treatment plant for balancing purposes, allowing greater operational flexibility.

Before being introduced to the pipe, solids need to be removed and the water chlorinated. Circular clarifiers and rapid gravity sand filters will reduce the level of sedimentation and the chemical dosing will disinfect and remove acidity.

Internal layers of epoxy coating will provide protection for the pipe from the treated water and an external layered bitumastic coating will work in addition to the cathodic protection. By incorporating these measures a 60 year design life can be assumed for steel pipes.

A booster pumping station lies 7km downstream of the treatment works and will increase the transfer capacity of the overland pipe.

Conventional water supply horizontal split casing pumps will be used, as they allow varying flow conditions and have standby provisions for repair and maintenance.

Surge control pressure vessels will be sited at the booster station, the coastal station and at an intermediate site 250km down the line. Chemical dosing will take place at these lower stations with any biofilm also being removed.

At the coastal station each of the three 1.42m diameter submarine pipes will have a horizontal multistage high pressure split casing pump, with a further two on standby. A balancing reservoir equal in size to that at the treatment works will also be provided upstream.

In addition to the protective measures used on the overland pipe, the submarine stretch will have a concrete outer lining, primarily used to increase the mass of the pipe to anchor it to the seabed.

Trenches along the seabed will be dredged by a giant Japanese-owned dredger, one of the largest in the world. In shallower waters of around 20m depth the pipes will be buried as a standard protection measure.

When the line reaches Kuwait the final section to be constructed as part of the scheme is a water transfer terminal. This includes chambers for the reception of cleaning devices, isolating valves, measuring equipment and communications systems to the control centre in Iran.

Reservoir storage, additional water treatment and pumping for the water's as yet undetermined end use will be provided by Kuwait's Ministry of Electricity & Water.

Completion is expected in 2005 but timetables are always subject to change when working in the Gulf. 'Already we've faced delays due to government changes and ministerial reorganisations, but that's just something you come to expect after a while operating in the region, ' says Clark.

On the ground Kuwaiti and Iranian private finance will each account for 35% of the total cost of the project with the remainder raised internationally.

Project co-ordinator Gulf Utilities is employing Binnie & Partners (Overseas) as its consultant design engineer for this scheme.

No contractors have yet been appointed.

Binnie is no stranger to this field of work with experience of large scale pipeline projects in places such as Bahrain, Botswana, Saudi Arabia, Jordan and Algeria.

'There's no doubt this is an international project, says Gulf Utilities director John Cox, 'but this time it's British led, because in the Gulf region British engineers are still regarded as the best in the world.'

Theories that the next internal Middle East war will be fought over water supply were rebuffed by Binnie director John Grimes, 'It's far more likely that by adopting such schemes these countries can come much closer together.'

Gulf Utilities' Brian Hendry agrees, citing the positive response and working relationship with the Iranian authorities. 'In recent years Iran seems to be becoming far more open and increasingly keen to work with its neighbours and the international community, ' he says.

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