Project manager for Grantham bypass explains 18-month delay and engineering challenges faced

A project manager of the Grantham relief road has explained its 18-month delay and the engineering challenges that his team has faced.

Back in December 2021, the team working on the Grantham southern relief road identified a section of soft, unstable ground where the new bridge over the East Coast Main Line and River Witham is being built.

With phase two of the project opening in December 2022, the bridge connecting the B1174 roundabout and Somerby roundabout represents much of the final phase of work before the relief road is completed.

Six piers were put into place to support the bridge in November 2022, but the structure will now need to span a further distance to by-pass the original embankment where the soft ground was discovered.

A spokesperson for Lincolnshire County Council (LCC) confirmed that the extra cost of the work will be around £15 million on top of the existing costs of £133 million.

It is estimated that the project should be completed by the end of 2025, around two and a half years later than initially planned.

Matt Morrell, external project manager on the bypass, said: “After the last set of piers, there should have been the end of the bridge.

“The issue that we had was that when we built that embankment just before Christmas a couple of years ago, we noticed that the embankment was starting to move.

“That’s pretty common, because you’re putting an enormous weight on the ground that it’s never had before, so movement is pretty typical.

“But we were getting really big cracks, not just in the abutment, but away from the abutment as well, so a lot was moving, not just the embankment.”

Matt, who is a chartered civil engineer with over 20 years’ experience, explained that there was a potential risk if the embankment failed that could have impacted on the rail movements below.

“We very rapidly removed that bit of the embankment and investigated what was going on,” continued Matt.

“We found that underneath, there was a sheet of rock that started to slip, so everything we built the embankment on was slowly starting to move down the hill. We had to come up with a solution to that.

“So what we’ve done, and it’s easy to say but much more difficult to do, is to extend the bridge. That means that we’ve got another 70 metres to span over that bit of rock.

“This is the most efficient solution and it is the best way to continue. It’s taken a lot of effort and input from many in the team to carry out – you can imagine how many hundreds of hours of thought have gone into it.”

When the crack was discovered months ago, Matt and many other senior engineers had gone on leave for Christmas.

He said: “From an engineering point of view, cracks in the new embankment wouldn’t have been as concerning but the fact that we hadn’t touched this, meant that something bigger was going on.

“There was a busy removal of this end of the embankment as quickly as we possibly could during that Christmas period.

“If I remember rightly, there were people out on Christmas Day checking it and working on it.

“There’s definitely a joy in resolving a big issue.

“[The bridge] is an incredibly beautiful structure. It will be an addition to the town.”

Councillor Richard Davies, executive member for highways at LCC, explained that the co-ordination of the ground investigation information and the subsequent design of the bridge was, and is, the responsibility of the bridge designer, WSP.

He added: “It’s unfortunate that the delays had an impact on the project’s original completion date, which now stretches beyond our original timeframe of late this year.

“And with the increases in costs across the board, in particular with the price of construction materials shooting up so much, it will cost more to get the road built – but that remains a cost that we still believe is far outweighed by the undeniable benefits it will bring to Grantham, and Lincolnshire as a whole.”

There have been some unsung successes relating to the project, which Matt says have caused “huge” savings of money and environmental impact.

A temporary bridge that runs through the viaduct over the River Witham allowed materials and equipment to freely cross from one side of the site to the other, without needing to drive through Grantham from the B1174 roundabout to Somerby roundabout.

Matt said: “Initially, the plan was that we would use road wagons to go into Grantham past McDonald’s and come back. Thousands of movements.

“Then [contractor] Galliford Try said, ‘let’s just build a temporary bridge over the river and thread it through the arch [of the railway viaduct]’, which Network Rail were completely happy with.”

Coun Davies added: “Imagine the thousands of hours of delays that this has stopped. Imagine what the centre of Grantham would have been like.”

Another positive of the project has been the reusing of materials, facilitated by an on-site processing yard, which can shape the lumps of limestone into the right sizes to be used to form the embankments for the bridge.

Matt said: “What we always try and do with these big projects is, we have what we call cut-fill balance.

“So you cut out and fill the same amount – it never quite works out perfectly but it depends on the ground that you’re dealing with.

“It’s a huge saving on money, truck movements. You’re not driving thousands and thousands of wagons through the middle of Grantham.”

The composition of the bridge piers will also save on costs.

Matt said: “We always used to paint bridges in the old days to make sure they didn’t rust. The problem with paint is that you have to repaint it every 25 years. What we have now is weathering steel.

“You make the steel slightly thicker than it needs to be and then it rusts, but the rust forms a protective layer around the outside, so the surface rusts, but the middle doesn’t, so theoretically, it’s zero maintenance during the lifetime of the bridge. It’s a very beautiful colour.”

Matt went on to explain the logistics behind creating phase two of the project, in which the team moved a section of the A1 10 metres to one side, while keeping it running.

“We had to keep the A1 open,” he said. “Whilst we built a new bridge through an embankment that the A1 is sitting on.

“We left one carriageway in place, and built a new one next to it and what was the northbound, became the southbound.”

Coun Davies added: “When you consider that the A1 is certainly in the top three roads in the region and possibly the country, how little noise we had. There were glitches and problems, but it was incredible.

“This is the positive side of local highways work, even with all the problems and delays, building something that you know is going to be there for generations to come and will fundamentally change things is brilliant.

“Anecdotally, people are saying to me that [phase two] has made life a little easier, because it gives them a much better access from the south of the town on to the A1 and off it.

“The impact will come when we can say, ‘right, we’re stopping HGVs trundling through the middle of Grantham’ because there’s no reason for it.”