A leaky rooftop deck at the Hawai‘i Convention Center will likely cost $50 million to repair. That’s almost double what Hawaii Tourism Authority had anticipated it would cost to complete the circa-1998 center’s largest deferred maintenance project.

Last year HTA said fixing the rooftop terrace would cost about $28 million, based on a 2012 report. But a forensic investigation completed earlier this year estimated the repair costs, including design fees, at about $50 million.

The estimate assumes that no significant changes are planned for the current rooftop terrace and that construction will start before February 2021. It doesn’t include loss of revenue from construction-related closures during the estimated 10- to 11-month repair job.

It’s a substantial reinvestment in a center that cost $200 million to construct.

Julian Anderson, whose company, Honolulu-based property manager Rider Levett Bucknall Ltd., said Thursday the study they conducted found cracks, rust, water intrusion, water leaks and mold. The problems were beyond those identified in 2012 when experts in water leaks were brought in to recommend fixes, which were never carried out, he said.

A 2012 report by engineering consultant Allana Buick &Bers Inc. said that “the deck is still safe to hold public functions on, but repair is highly recommended in the short-term of five years.”

Seven years later, Anderson said, “repair is not optional.”

“The cost of repair will continue to escalate as time goes on. There could be construction cost escalation and escalation of direct and collateral damage,” he said.

Anderson also recommended that HTA expedite another study to consider whether the agency should tweak the design or add anything to the rooftop terrace, which is the only spot where the facility has room to grow.

HTA Chief Administrative Officer Keith Regan said HTA’s new leadership team noted deferred maintenance upon joining the agency in December. They began addressing the center’s repair list and hired Rider Levett Bucknall, Regan said. The new report, which cost $320,000, brings the center’s total improvement cost to at least $77 million, he said. Costs could be higher if HTA decides to make major changes to the rooftop terrace, he said.

Regan said the HTA is in the process of hiring another consultant for about $70,000 to conduct an assessment of Hawai‘i Convention Center demand, its optimal square footage and its potential additional uses. “We want to make sure we are doing it right and with the proper analysis. At the end of the day, it’s what the governor, the Legislature and our board will support. We need to make sure that we all agree on what direction to move forward.”

In the meantime HTA already has approved spending $14.6 million from an $18 million maintenance fund kept by center operator AEG, he said. Those expenditures paid for the Rider Levett Bucknall report and will tackle replacement of a boiler, a cooling tower, a waterfall repair, a kitchen wall rehabilitation, the purchase of new banquet chairs, tables and decor and upgrading china, flatware, glasses and other bar and buffet items.

HTA has another $18 million in reserves for the center’s other repair items but will need to get additional state funding to complete the rest, Regan said.

Officials at the center requested about $27 million from the Legislature in 2017 to fix a leaky rooftop deck, but legislators did not approve the expenditure.

Regan said HTA has shown the most recent report to legislators but hasn’t yet requested funding because total costs have not been determined.