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Thirst for innovation

Cyprus is tackling chronic water shortages with a bold new programme of dam construction.Ian Lawrence reports.

Through summer, and on into autumn and winter, tourists flock from northern Europe to Paphos to relax in a spot of Cyprus sun.

But while visitors bask, for local households the warm sunny climate means water shortages.

Decreasing levels of rainfall have hit water flow into existing reservoirs, and most families have to go without water every other day.

Forced to take action or face drought, the Cypriot government's strategic water development plan includes construction of a number of new dams. Serving Paphos will be the Kannaviou Dam on the Ezousa river, to the west of the island.

The $30M scheme is intended to boost potable water supply to the 35,000 homes. 'With the dams, every cubic metre of water is extremely valuable, ' says Andri Havouzari, project manager for Kannaviou.

Work began in November 2001 by a joint venture of Greek contractor AEGEK and Cypriot firms Iacovou Brothers and Cybarco, and is on course to finish towards the end of next year.

The 75m high structure is the first concrete faced rockfill dam (CFRD) in Cyprus, says Havouzari.

AEGEK project manager Dimitris Glavas explains: 'It's an innovation because normally in Cyprus we use a traditional clay core. At Kannaviou there isn't enough clay.'

Instead about 1M. m 3of pillow lava quarried from the hills has been used to construct the spillway and main dam embankment.

Glavas claims the adoption of a concrete face design rather than clay core has offered significant benefits. It is easier to carry out a number of activities simultaneously, allowing faster construction, while the structure requires around only half the rockfill needed for a clay core dam. And the relatively dry internal structure of the concrete faced dam is more stable than the saturated structure of a clay core embankment.

The grouting method employed to create an impermeable curtain under the 650m long dam is still fairly new for Cyprus. 'It supersedes the traditional method whereby you start with a thin grout and thicken it up, ' says designer KBR's resident engineer Frank Cooper. 'With GIN [grouting intensity number] grouting you start with a thick mix and inject at a predetermined pressure, depending on the total amount you want to inject.

'The key is to apply consistent pressure to force open any fissures to get grout in. The advantages are that you can control the amount of grout that goes in and under what pressure you inject it.'

A monitoring system automatically shuts off the grouting if any uplift of the plinth, or base of the dam, is reported.

Havouzari adds: 'When we looked at the areas we have grouted [by drilling boreholes] to check the permeability we could see veins of grout. It's good quality stuff. Really hard.'

In addition to visual inspections and standard physical permeability checks, vacuum boxes have been constructed to test the brazing of copper waterstops used to prevent ingress of water to the dam core.

'The box sits over the waterstop. Then we seal it and apply the vacuum inside, ' explains Cooper. 'It tests the joints.' In initial tests, however, it was that vacuum box that leaked. Havouzari found an enterprising solution.

'We tried everything on the market but nothing worked. What we needed was play dough - the type you cook for small children to play with. Eventually we got the recipe from England, ' she recalls.

She is now overseeing the final stages of the concrete slab construction.

Glavas says: 'Although it isn't a particularly high dam of its kind, the face slab is very big. We have 40,000m 2- you'd usually find this amount only on 170m high dams.

The valley is very wide.'

Working 24 hour shifts, normally six days a week, enabled 18,000m 3of concrete to be placed between the end of August and the end of November, Havouzari says.

Casting was speeded by using a 15m wide slipform which requires less labour.

'The slipform slides on two rails placed on either side of the bay, starting at the bottom, ' she says.

'Concrete is delivered through chutes, made from old oil drums, on to a conveyor belt system, which distributes the concrete. The shutter moves at 3.5m/h.

Sometimes it can reach 4m/h, depending on various factors such as weather or height.'

Keeping the concrete cooler than 30infinityC to prevent thermal cracking and prolong curing time was a problem in the heat of the Cypriot summer. The site's isolated location meant bringing in ice would have been difficult, so instead the concrete was covered with hessian sacking and sprayed with cold water for 28 days.

AEGEK brought considerable experience to the project, having worked on a 150m high concrete faced rockfill dam at Messohora in Thessaly, central Greece, the highest of its type in Europe.

An ICE delegation visited the site earlier in the year, impressing director general Tom Foulkes.

'It's a very good example of the vigorous and imaginative approach that people in Cyprus have been taking towards civil engineering, ' comments Foulkes.

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