Scottish Water uses pipe jacking in Paisley
Scottish Water is using pipe jacking to complete the construction of a 1.6 km sewer tunnel in the town of Paisley in Renfrewshire, Scotland.
The £17 million (US$21.9 million) project reached a major milestone in April 2017, when the first of three microtunnel boring machines (MTBMs) arrived on site, ready to commence excavation.
The Paisley sewer project involves the installation of a large diameter interceptor sewer which will start at a carpark within the town’s limits, and pass under a nearby hotel, a local park, a railway line and even a train station. The project client, Scottish Water, selected a local contractor, Amey, to complete the work.
In addition to the sewer installation, the contract covers the installation of combined sewer overflows (CSOs) in the town centre. The CSOs will substantially reduce the frequency of spills from the sewer network in storm conditions.
Once completed, the new infrastructure will fundamentally alter the performance of the drainage catchment in Paisley and retain a lot more of the storm flows in the sewer network, meaning storm spills to the local waterways will also be substantially reduced.
The sewer line will be installed by the pipe jacking method, with individual sections of concrete pipe installed sequentially and jacked into position to the rear of the MTBM once the machine has removed the soil. The soil along the sewer route, which reaches depths of between 4 m and 20 m, is predominantly mudstone and siltstone.
The route of the sewer tunnel, and the method of installation, were chosen to minimise any disruption to local residents, road users and businesses.
In April 2017, the Paisley sewer project reached a major milestone when the first of three state-of-the-art MTBMs arrived to the project worksite in several pieces, ready to be assembled and lowered into the launch shaft ahead of excavation. This 7 m long MTBM – weighing approximately 12 t – will be used to tunnel the first third of the sewer line, which will be 1,200 mm in diameter.
Powered by an external hydraulic power pack, the machine will excavate approximately 45-50 t of earth per day, progressing at an estimated speed of 8 m/day. Dubbed ‘Abbey’, the MTBM will be operated remotely from a control centre above the launch shaft.
“We are delighted to have reached this milestone on the project, after a lot of preparatory work, and to have lowered the tunnel boring machine into position at the launch chamber,” said Project Manager Brian Boland.
“Once it was assembled belowground, the machine was presented to the rock face and has now started its work on boring through the earth and installing the pipe. After four years of planning this project, in liaison with the Scottish Environment Protection Agency (SEPA) and Renfrewshire Council, it is great that the tunnelling proper is now underway.”
The machine will install the first stretch of the tunnel, and two other machines will install the second and third stretches of the tunnel, which will be 1,500 mm and 1,000 mm in diameter, respectively. A total of 15 shafts will be excavated along the sewer route, with the MTBMs tunnelling between them.
The Paisley sewer project, which is the biggest of its kind that Scottish Water has ever made in Renfrewshire, is part of the authority’s £250 million (US$321.8 million) five-year program of works to improve river water quality and the natural environment and tackle flooding across the Greater Glasgow area. The overall investment, which includes the Shieldhall Tunnel in southwest Glasgow, is the biggest in the Greater Glasgow area’s wastewater infrastructure in more than a century.
Project works for the new Paisley sewer started in October 2016 are expected to take two years to complete.
This article was featured in the Summer edition of Trenchless International. To view the magazine on your PC, Mac, tablet, or mobile device, click here.
For more information visit the Scottish Water website.
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