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Engineering dreamland on Scotland’s largest-ever flood prevention job

A “civil engineer’s dream”, Elgin Flood Alleviation Scheme is the biggest flood prevention project in Scotland and is combining a variety of disciplines to protect the town from a one-in-200-year disaster.

Project Elgin Flood Alleviation Scheme

Client Moray Council

Main contractor Morrison Construction

Civil engineering consultant Royal Haskoning

Cost consultant EC Harris

Total cost £86m

Construction cost £50m

Elgin is one of Scotland’s oldest towns, with the settlement on the River Lossie first recorded in the mid-12th century.

It has grown along the river’s banks ever since and now has a population of more than 20,000. The Lossie regularly floods, with particularly severe events in 1997 and 2002. In the most recent of these, more than 200 houses were evacuated and 10 people had to be airlifted to safety.

Elgin is also situated on the A96 trunk road, the major highway connection between Aberdeen and Inverness. When major flooding occurs this road is often blocked, and the railway line between the two cities has also been severely damaged and closed for several weeks.

Clearly, preventing flooding would be of major benefit not just to local residents but to the wider regional economy.

Succession of schemes

Moray Council put together a plan to build five flood alleviation projects in the region, of which Elgin is the largest.

Three other schemes have already been completed in Lhanbryde, Rothes and the Burn of Mosset in Forres, with another at the River Findhorn and Pilmuir in Forres also under way.

“The same team has moved through all the projects. We’ve been able to work very closely together, which has helped on both programme and cost”

Allan Russell, Morrison Construction

The Elgin Flood Alleviation Scheme began in April 2011 and is due to finish in the summer of 2015. Once finished, it will be able to cope with a one-in-200-year flood. The 2002 flood was a one-in-65-year event.

Elgin FAS is the single largest flood alleviation scheme in Scotland to date and the largest-ever civil engineering project in Moray, with an overall scheme cost of £86m and construction costs of £50m.

Morrison Construction is main contractor for the project, and has worked on all four of the other Moray flood alleviation schemes. Allan Russell is a project manager for Morrison and is scheme manager for the Elgin FAS.

“The same team, including myself, has moved through all the projects,” he says. “It means we’ve been able to work very closely together, which has helped the schemes on both programme and cost.”

Range of disciplines

The team is building new set-back flood embankments and flood walls from Glen Moray Distillery in the west to the new confluence of the Tyock/Linkwood diversion channel with the River Lossie in the east.

The diversion channel for the Tyock is being dug to move that confluence 1.5 km downstream, with another relief channel built opposite Elgin Cathedral.

Morrison is also building three new bridges: Lossie Wynd footbridge, to replace Old Bishopmill Bridge; Brewery Footbridge, to span the new relief channel opposite the cathedral and form an extension to the existing listed Brewery Bridge; and a replacement for Pansport Bridge, which will be named Landshut Bridge after the Bavarian city with which Elgin is twinned.

“It has everything: major bridge, earthworks, heavy civil engineering, walls, roadworks and river diversions. It’s a civil engineer’s dream, really”

Allan Russell, Morrison Construction

The latter will match the existing Pansport Bridge’s alignment but will span both the existing river and the new diversion channel.

The 75 m two-span arch bridge will carry road traffic and pedestrians on a suspended deck. More than 600 tonnes of steelwork has gone into the bridge, with 1,460 tonnes of concrete required for the foundations.

“The steel structure is now in place and we are putting in the permanent framework. We hope to have that done by Christmas,” Mr Russell explains.

“Work at Mansion House Hotel and Glen Moray Distillery upstream is now complete and the new channel and flood embankments downstream are also mostly finished.

“We’re progressing with further earthworks now, but we will be at the mercy of the weather over winter on that.”

Work is about to start on large diversions at Lossie Wynd, which will take the rest of this year and all of next to complete.

Morrison is also about to remove an old railway embankment and bridge from the pre-Beeching era.

“Work on that will begin in the next few weeks – there we actually have to take out a water main and divert it away,” Mr Russell says.

Unforeseen events

One of the big challenges on the project has involved dealing with an unforeseen volume of asbestos.

“There was an industrial estate downstream which had to be relocated due to the construction of new walls, embankments and a flood plain,” Mr Russell explains.

“The local community have been very supportive – at the end of the day, it is a scheme designed to protect their homes”

Allan Russell, Morrison Construction

“When we lifted the concrete floor slabs, we discovered large amounts of asbestos that had been buried there 80 years ago. All of that was taken offsite by a specialist contractor.”

In addition to the large pieces, the team discovered areas where small particles and fibres had become mixed with the soil.

“We buried the contaminated soil inside concrete-capped cells underneath the wall and embankments,” Mr Russell says. “It was a more economic way of dealing with it.”

High profile

The project has been a high-profile one in the local area, with public engagement and consultation a crucial part of the scheme.

“We hold regular public meetings and the local community have been very supportive – at the end of the day, it is a scheme designed to protect their homes,” Mr Russell says.

“Working in a town like this, you’re always in the public eye. Pansport Bridge is a major structure being built in the centre of a busy town, so you have to take that into account.”

The project’s scale and diversity is something that appeals to the scheme manager, with a huge variety of disciplines on display.

“It has everything: major bridge, earthworks, heavy civil engineering, walls, roadworks and river diversions,” he says. “It’s a civil engineer’s dream, really.”

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