Kinloss - Outfall

“Both written and verbal communication between staff and

the AMEC team exceeded our expectations,” project manager, AMEC

Planes and helicopters flying from RAF Kinloss provide vital military defence and emergency support to Atlantic shipping. Visser & Smit Habab (V&SH) and VBMS (VBMS was part of V&SH till 2012) helped keep their way clear.

Facts and figures

Year of construction
2007
Specialties
Biggest drilling operation until that point
Project categories

The Challenge

RAF Kinloss on the Moray Firth, in the north east of Scotland, opened as a flight training school on 1 April 1939, just five months before the outbreak of World War II. These days, however, it functions as the base for three squadrons carrying out round-the-clock surveillance and search-and-rescue missions over the Atlantic. Its 2.3km runway has an area of over 100,000 square metres which - during an average year - will collect around 65 million litres of rainwater. A year typically brings five centimetres more rainfall than in London. All of this needs to be collected, carefully cleaned and carried to the deep water channel of the Moray estuary to meet strict EU environmental regulations. A roundabout route onto the beach had to be found to avoid disturbing the dunes, which are threatened by erosion. “And the fact that we were working on an RAF base meant the security side was intense, with our staff kept under strict surveillance at all times,” says V&SH’s David Lee, who handled client liaison.

The Solution

V&SH’s specialist expertise was called on in the summer of 2006 by engineering firm AMEC, which was committed to installing two underground outfalls to handle the waste water: one was to be 484m long and 630mm in diameter and made of polyethylene alone, while the other - with a diameter of 323mm and a length of 775m - had to be clad in a steel outer

The construction was carried out in four stages taking just under three months. The pipes were made up from sections on dry land: holes were drilled; the pipes were towed out to sea and pulled back into the holes; and, finally, special nozzles, known as ‘diffusers’, and protection elements were constructed on the subsea ends. The longer outfall could be drilled to the correct diameter in one single operation, although at the time its 323mm diameter made it the largest hole VSH had ever made by drilling a single pilot. The shorter one however, had to be much larger and so a hole had to be drilled and then a reamer passed through to bring it up to its target diameter. “After we had punched out through the sea bed, we then had to pull a reamer back through the hole twice,” explains project manager Scott Stone. A special kind of ‘drilling mud’ was used to lubricate the reaming process and to transport cuttings of soil and rock back to the surface, where waste material was extracted before the mud could be re-used. Despite the scale of the task, the only factor which managed to slow down construction for a couple of days was a spate of bad weather which meant divers could not safely go out to sea, says Stone. So the Scottish weather had its way, albeit briefly.

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