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Rise and fall of the Caspian

Marine engineers at Mouchel are investigating some strange happenings in the Kazakhstan port of Aktau. Matthew Jones talked to them at the company's Surrey headquarters.

Mouchel's director of marine environment, Ian Manser, reckons marine engineering can sometimes be 'a bit like being a detective'. But even TV super sleuth Inspector Morse has yet to face a case as strange as the fluctuating levels of the Caspian Sea in central Asia.

The Kazakhstan ministry of transport called Mouchel into the region amid a sense of rising panic in January 1997. The level of the Caspian had risen by more than 600mm in just four years, prompting fears that Kazakhstan's only sizeable port, Aktau on the sea's eastern shore, would be inundated.

Mouchel's mission, funded by a European Bank for Reconstruction and Development loan to the Kazakhstan government, was to ensure that an existing 2km long breakwater would withstand storm conditions for the higher sea level. But no sooner had the Surrey-based company taken on the project than the level of the Caspian mysteriously started to fall again.

'It's an enigma which nobody fully understands,' says Mouchel board director Michael Lohn, who is in overall charge of the project.

The detective work started by researching the historical variations in the level of the Caspian over the past 450 years. By piecing together information from institutes across Russia and Kazakhstan, Mouchel was able to show that the level of the Caspian was up to 4m higher in the early 19th century than at present, but that it fell rapidly from the 1930s onwards.

Lohn and Manser put this down chiefly to the development of heavy industry at that time and the damming of the river Volga - the main source of water flowing into the sea. They believe the collapse of industries following the break-up of the Soviet Union and changing weather patterns subsequently led to the sea's rapid rise to something like its natural level. But how does this explain the fact that the level is now falling?

'One of the arguments is that there is a peak sea level which is limited by the increased evaporation rate from the increased surface area. But no-one can say hand on heart that the sea level will not start to rise again,' says Lohn.

Because of this uncertainty Mouchel was kept on to investigate ways of raising the height of the Aktau breakwater should the need arise. But, as with all good investigations, it uncovered more problems with the structure in the process.

The breakwater was built in the 1960s to what Lohn describes as an 'unconventional' design. It is effectively composed of 40t concrete blocks piled on top of each other but has no central core of fine material to stop all the wave power crashing through into the protected harbour area.

This is all the more critical, says Lohn, because a number of multi- national companies now want to export oil from Kazakhstan's developing fields. Although a major pipeline to Novorossiysk in Russia is planned for the future, the port provides a useful short-term solution and will give Kazakhstan more political bargaining power with its bigger neighbour.

However, oil companies will only invest in the port if they are convinced it is reliable. So Mouchel's new brief is to cut down the number and size of waves which are able to travel through the breakwater and hence reduce the downtime of the port in bad weather.

The company has already carried out extensive numerical modelling of the wave climate inside the harbour, but this new problem requires a more detailed approach.

'To come up with a really cost effective solution we will have to purpose build and test a physical model,' says Manser.

This will be subcontracted out to a hydraulics research institute in the UK or Europe in the next few months.

The model will be built and run to the existing conditions and calibrated using measurements taken in the real harbour. It will then be used to test a number of different options to find the best way of reducing waves inside the harbour.

Potential solutions, ranging from £20M to £60M in cost, include applying more armour units to the outside of the breakwater, filling the breakwater with fine material or applying a barrier to the port side of the structure. But the most practical answer may be to create a sheet piled wall attached to an existing oil loading jetty 10m behind the breakwater, says Lohn.

However, the final decision will depend on the results of the physical modelling, which will be known in about a year's time. For Manser this is what makes it such an exciting way to earn a living.

'Marine engineering is not just something you can look up in the codes, you learn something new from every project. That's what makes it so fascinating,' he says.

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