The cost of one of the Bay of Plenty's largest roading projects has jumped to $262 million and it will be delayed by another year.
The Baypark to Bayfair Project, also known as Baylink or B2B, on State Highway 2 at Mount Maunganui will see flyovers built bypassing two busy roundabouts.
When the first sod was turned on this phase of the project in 2017, it was expected to cost $120m and be finished by 2020. The most recent estimate pegged the cost at $146m and the completion date in 2022.
This week, however, the New Zealand Transport Agency Waka Kotahi confirmed the estimate had risen to $262m, finishing in December 2023.
The increase will be covered by the agency.
Portfolio manager for Waikato and Bay of Plenty Jo Wilton said the increase was not just construction costs - it also included funding for elements such as design work and property purchases.
The delay in finishing the project was another "disappointment", she said.
"We are sorry it is taking longer but we are doing what we think is the right thing to be doing. We are investing in the mechanics and working to make sure it is finished to the best standard with the best quality as we can.
"We really do empathise with the local business owners and residents."
The agency was informing nearby residents via a mail drop yesterday afternoon.
About 36,000 vehicles travel through the project site on SH2 each day - more than the Southern Motorway, Winton said.
Transport agency project team manager John McCarthy said the delay largely came down to three unexpected issues.
"One was one that we didn't see coming – ground improvement. The second was a scope added back into the project - which was the underpass - and the third was Covid-19," he said.
"Covid has hit us in a big way."
Impacts included resources stuck in Auckland and international restrictions hitting imports such as steel supplies, pre-fabrication and steel lattices.
McCarthy said "unforeseen" issues with layers of pumice also created problems in stabilising the ground enough to prevent potential liquefaction problems.
Engineers probed and tested more than 100 places in the site before construction began, but some areas of pumice did not behave as expected.
"The issue here has been trying to understand the issue, then working out a way to try to resolve it."
The transport agency sought help from the University of Auckland. The new plan involved interlocking a network of 3500 stone columns to act as underground walls.
These are placed up to 15m under the highway and essentially frame key weight-bearing locations considered most at risk.
McCarthy said, however, the underpass had "pushed [the project] out the most".
Original project plans omitted the popular pedestrian and cycle underpass beneath the highway near Bayfair Shopping Centre.
After a community outcry, the agency agreed to include an underpass, but weight-bearing issues meant a new design was needed. All told, the underpass added $26m to the cost. Tauranga City Council agreed to pay $2m of that.
New underpass concept plans are expected to be released in the next few weeks.
McCarthy said the agency briefly considered walking away from the project but knew the improvements would still be needed in the future. The agency board decided to continue despite the extra cost and delay.
He said the phased build was one of the most challenging projects he had been involved in.
"The problem is it's a consecutive activity rather than concurrent activity. You can't build a bridge structure until the ground improvements are in place. It means it's nigh on impossible to throw more resources at it and make it go faster."
McCarthy said with the underground work mostly done, people would soon see things taking shape above ground.
Bay of Plenty Regional Transport Committee chairman Lyall Thurston said the council's highest priority was getting Tauranga and the Western Bay moving.
The committee was optimistic the project would meet the new deadline.
"I would say disappointment will be expressed by a lot of people in the Western Bay but they've held on this long, I just plead with them to stay positive and acknowledge this will be a major, major development in the Western Bay when it's finally opened," Thurston said.
Tauranga City Council director of transport Brendan Bisley said the project would ultimately have a positive impact on traffic and travel times and should reduce rat-running on other roads.
Including the underpass was worth the extra time, he said.
"The underpass is important to provide good connectivity for residents in the general area across the highway and for pedestrians and cyclists to safely cross the highway."
Bisley acknowledged the high traffic volumes in Pāpāmoa and Arataki making delays "difficult" and traffic slower than normal.
He said the council was looking forward to the completed project "as it will provide a good level of service for residents connecting onto and off the state highway while improving travel times for freight and traffic staying on the highway".
B2B Project - over the years
The project: Build two-lane flyovers on SH2 bypassing the Baypark and Bayfair roundabouts, connecting to SH29A.
2015: Work starts on phase one, moving a section of railway line.
2016: Phase one finishes. Petition launched to save highway pedestrian underpass after the Bay of Plenty Times revealed it was not in the plans.
2017: Phase two - building the flyovers - starts. It is expected to finish in 2020.
2018: NZTA announces with will include an extended underpass.
2019: Completion date revised to mid-to-late 2021. Agency says underpass no longer viable due to the $33m estimated cost. Hundreds of people stage a protest in an effort to keep it.
2020: NZTA confirms an unforeseen issue with pumice layers. It later announced it will create a new, longer underpass at a cost of $26m, of which Tauranga City Council would pay $2m. Overall construction costs increase from an estimated $120m to $146m.
2021: NZTA reveals the project finish has been delayed until the end of 2023 and will cost an estimated $262m.