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Army increases salt intake

TRENCHLESS TECHNOLOGY CONTRACTS

INSTALLATION of a new sea intake pipe for a desalination plant in Cyprus took only five days using a Tracto Technik (TT) Grundodrill 20S directional drilling rig.

The pipe will supply sea water for conversion into potable water at the Dhekelia Army Garrison. It was installed by TT Cyprus and its contracting arm Underground Technologies for client Cynero and main contractor NE Joint Venture and Atlas Pantou.

The rig, supplied by TT UK, installed the pipe without disrupting road traffic and offshore shipping in Larnaca Bay.

Before the intake pipe was laid, three other bores had to be drilled. These were formed by a Grundodrill 12G. Some 48m of 200mm diameter HDPE pipe was installed between the water pumps and the desalination plant and another 48m long, 110mm diameter pipe was laid for electrical supply cables which will drive the pumps.

The third bore was to install a 315mm pipe through an existing 400mm diameter concrete pipe over 100m. This was carried out using the slip-line technique but instead of using a winch and steel cable, the rig's steel rods were first pushed through the existing pipe and the new pipe pulled back as the rods were retrieved.

Finally, the main 132m bore out to sea was carried out. Ground conditions were sand and sandstone with an average bore depth of 2.6m below the seabed. A percussive hammer was used to keep the pilot bore on line as the alignment ran in both materials. A Digitrak MK III system was used to locate the position and depth of the sonde housing.

After the pilot bore was finished, divers and landing craft handled the heavier equipment such as back reamers and breakout tooling needed to make the rod disconnections/connections on the seabed.

The pilot bore and three pre-reaming bores were carried out in only five days. The pilot bore took seven hours to complete and the first pre-reaming operation, using a 355mm back reamer, took two hours. The second prereaming operation used a 450mm back reamer and installed the 144m long, 315mm pipe and took just one and a half hours.

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