DENVER (CBS4) — A consultant hired by the City of Denver has generally given DIA’s concrete passing grades, but has recommended concrete testing at the airport be expanded from the terminal to the airport’s parking structures, garages and tunnels and be repeated in five years to make sure a problem known as ‘concrete cancer’ is not found in other parts of the airport.
The new developments were contained in a disclosure statement released by the Department of Aviation this week, and follows earlier concerns about concrete strength at DIA that have led to delays and projected cost overruns in the $650 million dollar Great Hall Project.
The City plans to follow the consultants recommendations but says “It is too early to determine the impact, if any, of the results of additional testing on Airport operations, or associated costs.”
CBS4 previously reported that the developer of the Great Hall Project estimated current cost overruns at $310 million and a possible 38-month delay in opening the new terminal due in part to issues with the terminal’s concrete.
The Great Hall Project – redeveloping the terminal to alter TSA checkpoints, add retail space and improve passenger capacity – was started in 2018 and was supposed to be completed in 2021. But in internal reports, not made public but obtained by CBS4, the developer has said issues with the concrete and other concerns may increase the price to $960 million and push full completion of the project back to 2025.
In 2018 as the project was underway, testing determined some of the concrete in the terminal was not as strong as previously believed. Construction came to a halt in some areas as more testing was ordered. Some evidence of what is known as alkali-silica reaction (ASR) was found in the airport terminals 25-year-old concrete and in its foundation. ASR, also known as “concrete cancer,” can lead to a swelling, cracking and weakening in concrete.
In a letter dated May 28, 2019, an engineering firm hired by the airport recommended additional testing for ASR in the airports concrete. The firm said concrete strength in the terminal floor is adequate for continued safe use and concrete cores from walls and foundations show it meets or exceeds needed strength requirements.
However, detailed examination of concrete from some parts of the Terminal foundations “shows trace amounts of ASR have occurred, but the extent of ASR is not destructive…” The company went on to say “The limited amount of ASR that has occurred… does not pose an immediate threat to the structure.”
Mayor Hancock and airport officials have repeatedly said the airport remains safe and safety is their number one priority.
The engineering company did however recommend additional testing of foundations located around the perimeter of the garage structures adjacent to the terminal, additional concrete testing in concourse structures, parking structures, tunnels “and other significant structures, and in five years, a repeat of testing foundation elements previously tested to determine if significant increase in the trace indications of ASR in these elements has occurred.”
Commenting on the newest concrete disclosure, Stacey Stegman, a DIA spokesperson, told CBS4 “The good news is that the Great Hall project allowed us to discover potential issues with the concrete, which was placed 25 years ago. We are doing our due diligence through extensive testing of the concrete so that we can address any problems and protect the airport for the future.In the meantime what is most important to know is that the airport is safe for passengers and employees.”