Organizers of the International African American Museum said Thursday that rising construction expenses will require them to raise another $10 million but that they still plan to start work next spring.

Inflation and trade tariffs are among the biggest budget busters. They've increased the cost of the museum about 20 percent, officials said.

"We understand that we're in a robust construction climate. We were prepared for increased costs," said former Charleston Mayor Joe Riley, a longtime supporter and ambassador for the project. 

Museum fundraisers passed their original $75 million goal in August. Afterward, Charleston City Council hired a construction manager and began soliciting bids. Project leaders recently learned the estimated cost of building the planned Concord Street structure had climbed to about $53 million from $43 million.

Riley said the price increases are across the board, from steel to labor. 

"Everyone's busy," he said. "In the construction industry, like in farming, you make hay while the sun is shining.... That gives us more work to do."

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Citing inflation and the rising cost of materials, International African American Museum CEO Michael Boulware Moore (left) and former Mayor Joe Riley said they need to raise another $10 million for the project. Wade Spees/Staff

In response, officials are moving money that was supposed to pay for exhibits and furnishings to the construction budget to ensure work starts next year as previously announced. The construction management team also will be looking to trim costs wherever possible, a process Riley called "value engineering."

"They always ... have the pencil-sharpening exercise to go through," he said. 

Riley described the $10 million target as "modest."

"We're confident we will meet this challenge," he said. 

About $6 million already has been pledged or identified. It includes about $1.5 million that came in after the original $75 million goal was met in August, Riley said.

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Also, this week, Anita Zucker of The InterTech Group agreed to double her original 2015 donation of $1 million, and an undisclosed corporate donor pledged $1 million. A third supporter has committed to a $2.5 million gift that will be announced later, Riley said.

"We're well on our way," he said, adding that he didn't want to discourage would-be donors.

"This will be a robust institution," he said. "We'll never have a problem with too much money raised."

Riley has been pushing to complete the project since he announced the idea at his 2000 swearing-in ceremony, declaring that the city would be home to a museum honoring African American history and heritage. 

Officials will be sticking to the current schedule, CEO Michael Boulware Moore said. They plan to present a construction contract to the city in late January, break ground in May and open the doors in mid-2021.

Like Riley, Moore is confident donors will step up. He noted that 2018 has been the most successful fundraising year yet for the museum.

“We’re seeing a lot of momentum, a lot of energy,” he said.

Emily Williams is a business reporter at The Post and Courier, covering tourism and employment. She also writes the Business Headlines newsletter, which is published twice a week. Before moving to Charleston, her byline appeared in The Boston Globe.