FOR weeks it has been the cause of rush-hour tailbacks coming in and out of Southampton.

Now a month after work started on Millbrook Roundabout the project is about to enter its second phase.

But before that starts, the Daily Echo was given a behind-the-scenes look at the £8.3 million scheme.

So far it has involved 15,000 tonnes of excavated material, 2,000 tonnes of asphalt and 400 tonnes of concrete.

Those are some of the results of the “humongous amounts” digging involved in an £8.3m road improvement project.

From Sunday the north-west lane running past McDonald’s on to Wimpson Lane will reopen to motorists, while the southbound lane on Tebourba Way will be closed ready for the start of phase two.

Now managers of the Millbrook site are preparing for phases two and three of the improvements to the roundabout.

In phase three, which bosses predict will be the most impactive on traffic, the entrance to dock gate 20 will be closed.

Lorries will be diverted further along the road to Dock Gate 10 where they will enter the port.

Balfour Beatty’s Vanessa Veal said: “Phase three without a shadow of a doubt is the biggest in terms of traffic.

“The fourth phase is the easiest in terms of traffic. With phase three you won’t be able to get out on Third Avenue.

“We can’t make people use a diversion route but we have had significant communications with DP World about the diversions.

“We shouldn’t get lorries going into the city centre.”

She added: “The roundabout is a failing structure – we have got to go down to virgin ground.

“It’s a significant depth of construction and the deepest dig we’ve done.”

Workers have dug 1.1 metres into the ground to relay rubble in a bid to stop the road from wobbling.

It’s the biggest city council road improvements operation since 2013, when the dual carriageway was put in at Platform Road at a cost of £13 million.

Site manager James Poole said: “It’s a humongous amount to dig.

“The roundabout is seen as nationally important. It’s about future-proofing – the port is about to have a massive influx and be expanded.”

As the site is on top of the ancient Millbrook pond, extra work had to be done to contain the water: “We had to do a bit of extra digging and had to put in a free drawing stone to make sure any water drained off.”

As reported, ABP has already started its £12 million port upgrade which will allow bigger and more cruise ships to dock in Southampton.

The roundabout will reopen between phases two and three – from December 20 to January 7.

High containment kerbs have been installed at the roundabout to allow for the size of lorries using the route – which number up to 4,000 every day.

The work has been guaranteed for the next 15 years.

The effort clashed with emergency roadworks at Totton and Western Esplanade.

Transport boss Councillor Jacqui Rayment, pictured left, said: “Please bear with us as we work to rebuild this important part of the road network. We must invest now to secure a successful and sustainable future for our city.

“Some disruption is unavoidable but we are making every effort to minimise the impact of this work on residents and commuters.

“Closures and diversions will be clearly signposted.”

Following the Christmas break, phase three of the work will start on January 7, running to March. This will require shutting off the slip-road from Millbrook Road West on to the roundabout, as well as the exit from the roundabout onto First Avenue – which leads to Dock Gate 20.

Phase four, from March to late-April, will see the closure of First Avenue (northbound) up to the roundabout and part of the slip-road onto Redbridge Road up to the junction with Second Avenue.

The council has confirmed that work will stop over Christmas and the flyover will stay open during the work.