MARSHALL — Replacing the city of Marshall’s Aquatic Center will be a big job. And even if Marshall extends a local option sales tax, the project may still need some additional financial support, city staff and officials said this week.

During a Tuesday work session, Marshall City Council members saw three different possible design concepts for a new aquatic center. The concepts ranged in cost from $19.5 million to more than $22 million, said landscape architect David Locke of engineering firm Stockwell. However, the sales tax extension the city is seeking to pay for a new aquatic center only allows for $18.3 million in sales tax funding, Marshall Mayor Bob Byrnes said.

With factors like inflation, the city may see funding gaps in the aquatic center project, said Byrnes and Marshall City Administrator Sharon Hanson. They said the city could work to address those gaps through other means, like sponsorships.

“We think there is going to be community support out there,” Hanson said.

At the work session, Locke shared possible design concepts for a new aquatic center. One of the main differences among the three concepts was the size of the lap swimming pool. One concept had a 25-meter pool. Another concept had some extended 50-meter lanes, and the third had a full 50-meter pool.

The 50-meter pool and extended lanes could be used for competition swimming practice, Locke said. However, they would be more costly to include in the project.

Locke said the base concept for the aquatic center would currently have a cost of about $19.5 million, including contingency and design costs. The option with a full 50-meter pool would add $3.1 million to the base concept cost.

In discussion, some city council members said they thought Marshall residents would have a hard time supporting an aquatic center project that cost more than $20 million.

“I think that’s a hard sell,” said council member James Lozinski.

Even if the city works to keep the cost of the new Aquatic Center lower, it was also possible they could have a funding gap, Byrnes said.

Hanson said the city wanted to pursue raising funds from community sources like sponsorships in addition to using sales tax revenue. She said city staff would also work with Stockwell to try and reduce costs closer to what would be allowed for sales tax.

The city is currently waiting for state approval to hold a referendum on whether to extend the time that Marshall’s local sales tax is in effect. Once they get approval, the question would go to voters.