Project Briefing

Perco breaks another auger boring record

RWE N Power

Locaton: Newark on Trent

Technique: Guided auger boring

Main Contractor: Alstom

Sub-Contractor: Laing O'Rourke

The end of March saw the completion of a record contract for Laing O’Rourke at Staythorpe Power Station, currently under construction in Nottinghamshire. The total of 17 under-track rail crossings (UTX) installed is thought to be the largest single auger boring project ever undertaken in the UK.

The UTX installations were required to enable power cables to pass under the double-track Nottingham to Newark railway line, connecting the new power station to the national grid. Using two Bohrtec BM 400 auger rigs, our teams worked out of two separate, concrete launch pits constructed by the main contractor. The pits were 30m long by 7m deep, allowing a depth of 5m from rail track level to the plane of the guided auger bore shots.

Spaced 3m apart, nine shots were made from the first pit, with eight being made from the second. Each shot installed 28m of 450mm OD Naylor Denlok clay pipe, ready to accept the client’s MDPE ducting to carry the power cables. Our engineers then grouted the annulus between the clay and MDPE pipes.

Ground conditions varied across the 17 auger boring operations, from heavy clay soils to sand and ballast. The team worked round the clock on 7-day weeks and carried out all lifting operations. Although delays were encountered the work was completed in just five weeks, well within the programme.

As work progressed, trains ran normally without speed restrictions. With no track possession required, rails were constantly monitored for heave or settlement but no significant movement was detected.

Staythorpe is being built by RWE npower and Alstom on the site of a former coal-fired power plant. When complete, the new gas-fired station will provide up to 1650MW of electricity.