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Tunnelling near Kilmarnock

24 November 2017

Tunnelling under A77

Tunnelling under A77

View footage of the work here.

Scottish Water has tunnelled under a major road in East Ayrshire to avoid traffic disruption, and beneath a river to reduce the impact on the aquatic environment, as a project to improve services to more than 200,000 people progresses.

Caledonia Water Alliance (CWA), Scottish Water’s alliance partner, used state-of-the-art Tunnel Boring Machines to install a section of a major new water main under the A77 near Kilmarnock and to lay another stretch of the pipe beneath the River Irvine near Hurlford.

A 67 metre-long steel pipe, and a 60 metre-long concrete tunnel with a 1.2m diameter to house it, were installed under the road about three miles south of the Bellfield roundabout.

The tunnelling work, which started in mid-October and took five weeks to complete, was done without requiring any road closure or lane closure and so no disruption to traffic occurred.

If the contractors had excavated and installed the pipe using the open cut method, the work would have required at least a lane closure or closures with temporary traffic lights on the A77 or possibly a full road closure.
CWA also installed a 70 metre-long stretch of tunnel, built out of 1.5 metre diameter concrete rings, about four metres below the river bed of the River Irvine west of Hurlford between the A77 and the B7073.

About 275 tons of material was excavated by the TBM. The tunnelling method meant the work had no impact on the river and the aquatic environment. If CWA had excavated a trench to install the pipe this would have required a diversion of the river.

Sean Lavin, Senior Construction Manager, said: “We are continuing to make good progress with the project and this latest piece of work near Kilmarnock is a very important part of that.

“When planning the work, we did everything we could to minimise any disruption or inconvenience to road users. We recognised how busy the A77 is at this location and that is one of the reasons why we opted to construct a tunnel, which doesn’t require any roadworks.

“In addition, although we previously diverted a stretch of the Craufurdland Water further north to install a stretch of the same water main beneath the river bed, we decided to tunnel beneath the River Irvine at Hurlford.

“This was because trenching and diverting the river would have been much more difficult due to the size of the river and lack of space at the crossing point and because it would have been much more disruptive. At all times during this project, we try to do whatever we can to minimise disruption to road users and the natural environment.”

As part of the same project, Scottish Water and CWA installed 3.8 miles of plastic pipe north of the Fenwick area at Glenouther Moor from Highfield Road to the Corsehouse Water Treatment Works off the B769. This included a stretch under the M77 and A77 near South Drumboy Farm.

The technique used was Horizontal Directional Drilling, a trenchless method of installing underground pipe using a drilling rig on the surface. HDD enables us to minimise disruption and avoids the need for road traffic management.

This tunnelling and drilling work was carried out as Scottish Water progresses with the second phase of a £120m investment in the drinking water network which will benefit more than 200,000 people and businesses in much of Ayrshire and parts of East Renfrewshire.

The second phase comprises the installation of about 13 miles of water main from the Amlaird Water Treatment Works in the Fenwick Waterside area to Highlees Pumping Station near Dundonald in South Ayrshire.

This section of water main will follow a route from the east of Fenwick, skirting the east of Kilmarnock and running west across farmland to Highlees.

Another 13 mile-long stretch of  water main, from near Newton Mearns, East Renfrewshire to the Fenwick Waterside area in East Ayrshire, and a pumping station at Darnley, has already been constructed as part of the overall project.

Scottish Water announced in December 2015 that it will improve the water supply network by installing more than 30 miles of new water mains to connect the system in Ayrshire with the Greater Glasgow area’s network.
The new and expanded network will enable Scottish Water to provide customers with greater security of supply and to respond more effectively to operational issues such as burst water mains and minimise disruption to customers.

Customers across a large part of Ayrshire currently receive their water from a single source, the Bradan Water Treatment Works, south of Straiton in South Ayrshire.
The water is supplied to customers’ taps via a 34-mile-long trunk water main installed about 50 years ago from the Bradan Water Treatment Works to the north of Irvine.

The construction of the new strategic water main, which is expected to be completed in 2020, will connect the Bradan water supply network to the network served by the Milngavie and Balmore water treatment works, north of Glasgow.
When complete, the investment will enable Scottish Water to transfer water from Glasgow to Ayrshire, and vice-versa if required.

This will create a larger, more robust and connected supply zone which will benefit customers in areas such as Ayr, Prestwick, Kilmarnock, Troon, Irvine, Fenwick, Galston, Stewarton, Hurlford, Maybole, Eaglesham and Newton Mearns.