A new subdivision in a flood-prone section of West Ashley faces a challenging road forward under Charleston's new building regulations. 

The Harmony project, which was slated to include more than 200 homes by national firm D.R. Horton, initially won  City Council's approval in 2015. Developers met with the city's Technical Review Committee Thursday, one of the last steps before work can begin on the 166-acre site near Glenn McConnell Parkway and Bees Ferry Road. 

Because the city recently instituted new building regulations in that area, part of the Church Creek basin, Harmony's developers were told they will now face much stricter regulations that require completely redesigning — or perhaps even scrapping — the neighborhood. 

The requirements of the updated regulations "changes their design significantly, I would expect," said Kinsey Holton, the stormwater program manager for the city of Charleston. While other ongoing projects have been affected by the new regulations, Harmony is by far the most significant, he added. 

The principal designer of the project did not respond to multiple phone messages Friday, but attendees of the TRC meeting said the news did not go over well. 

“The developer seemed quite concerned about the financial implications," said Betsy La Force of the Coastal Conservation League.

Charleston had paused building around Church Creek until it finalized new development rules last fall. The drainage basin comprises thousands of acres on the edge of the city that formerly was marshland and phosphate mines but  slowly been sectioned into suburban housing developments.

One group of condos flooded so frequently that it's the subject of a federally funded buyout program by the city to mitigate future flood damage. 

Harmony's developers knew Charleston was changing its rules when they met with city officials during the construction moratorium in 2017, Holton said, but they continued to move through the approval process. 

"They proceeded at their own risk, and they were well aware of that," he said.

One of the principal problems near Church Creek is fill dirt, which is trucked in by developers to raise housing lots. Raising new homes is required in flood-prone areas by the Federal Emergency Management Agency. Doing it with fill dirt disrupts the natural function of a floodplain, however, which works as a waiting area for water as it drains into a nearby stream or river.

Under Charleston's new rules, developers have to compensate for any new fill in a floodplain by digging a hole to hold any water that might be displaced. 

Because so much of the Harmony tract is now treated as a floodplain by the city, developers will have to offset just about all the fill they bring to the site. That decreases the buildable land, which may mean fewer housing units and ultimately, less revenue. 

The Conservation League previously urged the city to buy out the Harmony tract to stop development there. La Force said the pause that's been put on Harmony signaled a changing tide in how the city deals with building in flood-prone areas. She said the same rules should be applied city-wide.

“We’re pleased and relieved this is not going forward," she said. 

Charleston City Attorney Susan Herdina said it's not certain what will happen next, particularly whether the developer will challenge the new rules in court.

"I can tell you that the storm water guidelines for Church Creek were vetted with legal repeatedly," she said. "We discussed them, and we are certainly standing behind them and are prepared to defend them."

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Reach Chloe Johnson at 843-735-9985. Follow her on Twitter @_ChloeAJ.

Chloe Johnson covers the coastal environment and climate change for the Post and Courier. She's always looking for a good excuse to hop on a boat.