DENVER (CBS4) – The developer remodeling Denver International Airport’s terminal — the Great Hall Project — has told the city and the airport that concrete issues, change orders and delays will add an estimated $310 million to the project’s $650 million price tag — a whopping 47% increase. The delay in completing the project has jumped to 38 months, according to sources familiar with the terminal redevelopment.

Mayor Michael Hancock termed the numbers “alarming” during a 15 minute interview Wednesday with CBS4, but said, “This is a one-sided perspective that you are looking at.”

He said the numbers obtained by CBS4 come from the project developer — Great Hall Partners — and are unsubstantiated and have not been fully investigated and vetted by the City of Denver. Hancock said the city is in the midst of that process, with experts combing through the cost and delay assertions coming from Great Hall Partners.

“That’s not a bill, it’s their perspective on looking at the project. We’re not done with our analysis. It’s a long process that we have to complete before the final numbers are known”, said Hancock.

This marks the first time anyone involved in the terminal project has put a specific number on how much construction delays and cost overruns might total.

Great Hall Partners is a group of construction, financial and engineering firms led by international airport developer Ferrovial.

The new information about hefty cost increases and lengthening delays comes from sources familiar with Great Hall Partners and their evolving construction timeline and cost calculations.

The Great Hall Project, which is redeveloping the terminal to add retail space, moving TSA checkpoints, and improving passenger flow, started in 2018. It was initially supposed to be completed by 2021.

But not only would the new internal GHP estimates dramatically increase the terminal redevelopment price from $650 million to $960 million, they would push the completion date back from 2021 to at least 2025 according to sources familiar with the project.

“We are not going to allow the City of Denver or the airport to be taken advantage of,” said Hancock. “You have my word on it.”

In February, CBS4 first reported that concerns about concrete strength in the 25 year old terminal were causing delays in the Great Hall’s completion timeline. Early testing showed some concrete in the terminal was weaker than expected and that cracking could be seen in some of the terminal’s concrete. That essentially brought some construction work to a halt as more concrete testing was performed.

Hancock pegged much of the blame for increased costs and delays on the concrete concerns, but continually emphasized the priority for him and his administration is making sure the airport remains safe and ongoing construction does not jeopardize safety.

But new information from sources familiar with Great Hall Partners’ assessments, suggests bundles of change orders from DIA officials are proving similarly problematic and costly. The developer contends airport officials have asked for numerous change orders sending project costs soaring.

“I’m well aware of their thoughts around change orders,” said the Mayor. “We have our own opinion of how significant they are or are not.”

Earlier this month, on May 15, Great Hall Partners disclosed the projected delay in completing the terminal would be 20 months. But new internal GHP delay estimates, not made public but obtained by CBS4, say the delay could actually be as much as 38 months, meaning the new terminal would be completed in 2025, four years behind schedule.

Asked who would pay for cost overruns, Hancock said it was too early to discuss additional costs and who would absorb them.

CBS4 has learned the City of Denver is considering all of its options, including potentially terminating the current contract with GHP. Hancock said it was too early to discuss that scenario either.

“We still hope we can deliver a Great Hall Project we can all be proud of. Let’s leave it at that until we get all the information we need,” concluded the mayor.

The City of Denver and Great Hall Partners are now planning to meet with a mediator in June to address disputed claims and costs.

Alana Watkins, a spokesperson for Great Hall Partners, declined to discuss specifics but issued the following statement:

”Great Hall Partners is engaged in ongoing conversations with DEN about the forecasted delay, possible mitigation efforts and potential costs, which we anticipate will reach a conclusion by the end of the summer. Throughout this process, we continue to work closely with DEN to deliver the Great Hall project to the City of Denver and its community. We are grateful that our team has been entrusted with this project by DEN and the City and County of Denver.“