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Change of direction

A project to run a large irrigation pipe under a drainage channel in Egypt's Western desert was originally intended to be carried out using microtunnelling and was scheduled to take six months. Water from the Nobaria Canal, one of the country's major irrigation canals, was needed to supply a new farming area.

In the event Egyptian irrigation specialist Bonian completed the job in a month and at half the projected cost, using horizontal directional drilling.

Although the length of steel pipe was only 80m, with 175m of drilling required, its 600mm diameter added a challenge.

Further difficulties were the 8m depth and the ground conditions, a mixture of clay and sand best described as quicksand.

Absolute accuracy in the angle of the pipe was the first challenge. The water had to run from a small feeder pipe on the irrigation canal to a manhole from where it dropped nearly 4m into the pipe which carried it under the canal.

Using its Vermeer D50x100A rig, Bonian was able to adjust the slope so that the pipe emerged exactly level with the distribution channel, avoiding the need for further pumping.

Experimentation was needed to get the correct bentonite mix for the difficult ground conditions, but once this was achieved the job progressed smoothly.

With the pilot bore in place, Bonian reamed in stages, first to 300mm diameter, progressing to 400mm and finally 800mm. The pipe was then pulled through.

The success of this job has led to others. Bonian was asked to install a gas pipe under a railway line and since then has carried out other crossings for the gas company.

To handle the increased workload Bonian has invested in a second Vermeer D50 x 100A rig and the company is also branching out into pipe bursting.

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