WADMALAW ISLAND — Charleston County has paid at least $14.8 million to reserve credits from a planned wetland mitigation bank whose future is now in question.

According to a copy of the county’s Aug. 31, 2021 agreement with Point Farm MB and American Mitigation Co., it bought into the bank to offset salt marsh impacts from transportation projects. Among those projects is the planned extension of Interstate 526 through Johns and James islands.

The county committed to buy 440 salt marsh mitigation credits at $45,000 each, according to a purchase agreement signed by County Council Chairman Teddie Pryor.

A deposit of $14,850,000 was due within 30 days of the effective date of the agreement to reserve the credits, or 75 percent of the total purchase price. County spokeswoman Kelsey Barlow confirmed April 7 the money has already been paid.

Mitigation banks are private commercial entities that are meant to offset wetland destruction elsewhere. Federal law requires building projects to avoid harming wetlands. And if that isn’t possible, developers must pay to create more wetlands in the same watershed where the old ones were destroyed.