27 May 2016

Flooding should be a thing of the past for a group of Kent householders after the Eight2^O consortium, of which Costain is part, installed a new drainage system.

Residents in Court Road, Orpington, have endured such flooding repeatedly over the past 20 years. Eight2^O was given the task of solving the problem as part of its AMP6 wastewater infrastructure programme for Thames Water.

Before getting down to work, the team sent out a questionnaire to local homes, as well as carrying out surveys on properties, the surrounding area and the local sewer system. The resulting data was used to design a solution.

The team discovered that some residents had been unfortunate enough to have suffered from such backflows of contaminated water three or four times in the past five years.

To remove the problem, the team proposed laying around 200 metres of new underground pipes to take away storm flows.

“The solution was to install new pipework through Priory Park and across Court Road, the main A-road in the area,” said Project Manager Paul Clough.

The initial plan was to undertake a standard open-cut procedure across Court Road, digging down three to four metres to bury the new pipe. However, this would have caused considerable traffic disruption.

“So in collaboration with Bromley Council, utility service providers and our design team, we altered the original installation methodology, opting instead for an innovative trenchless technique that used auger bore tunnelling and pipe jacking.”

This meant tunnelling under the road, using the excavations for new manholes in the road verges as temporary launch and reception pits. “The auger acts like a large corkscrew 500mm in diameter, rotating within a steel casing. It transports the earth beneath the road back into the launch pit, from where it can be removed,” explained Paul. “Once the auger reaches the reception pit it is retracted in sections, allowing the sewer pipes to be progressively installed using hydraulic jacking equipment. This pushes the steel casings into the reception pit for removal and re-use.

“We were able to install the new section of pipe under the road with zero impact on traffic, much to the delight of Bromley Council and the local residents.

“Responding to concerns expressed at an initial public consultation meeting, we ensured that residents who were directly affected always had access to their driveways, or alternative parking, in order to minimise inconvenience as much as possible. Our construction team also liaised with Bromley Council to give local jobseekers the opportunity to re-seed along the excavation line within the park.”

The work began in early January and finished a week ahead of time just before Easter – just in time to cope with the Bank Holiday weekend deluge, which passed off without any problems for the relieved residents.

 

Ends

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