The city of Charleston is preparing to issue new design standards that aim to better control stormwater, but some experts worry the revisions could worsen flooding conditions in parts of the city.
The city has been working on revisions to its stormwater design manual since the summer of 2018. Since then, city staff has been working with AECOM, the engineering firm Charleston hired to help revise the manual, and a stakeholder task force to modify Charleston’s stormwater regulations.
The manual was initially finalized in January 2010, and this is the first major revision since 2013. The updated manual is expected to go into effect July 1.
Matthew Fountain, director of Charleston’s stormwater management department, listed the goals for the manual update:
Fountain said that the revised manual tries to take into account the recommendations made by the Dutch Dialogues report released in September but that it also has to consider the local experience and legal framework.
“We need to incorporate the knowledge we’ve gained from working in the area as well and say, ‘How do we put these two ideas together?’ ” he said.
For example, Fountain said, the stormwater design manual can’t outright ban “fill and build” without a technical justification, though the Dutch Dialogues recommend discontinuing the practice.
Instead, the revised manual has stringent requirements for how to use fill material in order to avoid runoff and flooding onto neighboring properties.
“Stormwater code is in between something like fire code, where it’s immediate public safety, and zoning code, which is how does the city want the city to look,” Fountain said, adding that stormwater code only works if the city bases its design regulations on real property damage and safety considerations.
“Development will look very different in the low-lying flooded areas. … And to me, that’s a very important part of what the manual is doing, because if we say all these changes made don’t change how we develop, well then we’re still in the same problems we have,” Fountain said.
The updated manual also adjusts the stormwater review fees that developers must pay. The current fees are $100 per acre disturbed by development; the updated manual says most construction will be required to pay a $500 flat fee and then $200 per disturbed acre, up to $5,000. The exception is single-family residential construction with less than a half-acre of disturbance, which will pay a $100 flat fee for review.
Fountain said the city is increasing the fees to increase the parity between the current fees and the cost of reviewing applications — though the updated fees still won’t completely cover review costs.
Patrick Arnold, executive director of the Charleston Homebuilders Association, said the revised manual makes significant progress toward flood mitigation in the city, but he said, “The concern is grave among our engineers and builders right now that this isn’t ready.”
Engineers from firms across the region, including HLA Inc., Forsberg Engineering & Surveying Inc. and SeamonWhiteside, sent the city 456 comments on the revised manual, asking for changes or noting concerns.
“I believe that staff understands and disagrees with a lot of the outside engineers’ perspective,” he said. “Or do not have the time or capacity to address some of these concerns right now.”
For example, Arnold said, engineers have asked the city to create models and test cases to demonstrate how the new regulations would work, but “that’s going to require a lot of staff time to do … and staff is already pretty limited.”
Mayor John Tecklenburg stressed to City Council that the revised stormwater design manual would be a “living document” and that any changes or modifications wouldn’t require another 18-month process. City Council passed first reading last month, with the intention of reviewing its effectiveness in February 2021.
Arnold said he understands the appeal to policymakers of having the freedom of an easily modified document, but he said it creates problems for developers and engineers who rely on the manual.
“Treating it as a living document sounds good and well, but it also creates uncertainty in the development approval process, which already can take up two to three years to have projects approved,” Arnold said.
Tecklenburg asked that the manual not be brought up for second and third readings until the city convenes another meeting to educate the public and potentially another task force meeting.
Arnold said the manual doesn’t need another public meeting; it needs a meeting of engineering professionals and city staff to address the remaining concerns.
“We’re looking for engineering workshops to get into the nuts and bolts of resolving these outstanding technical problems,” he said. “These aren’t things that the public even understands. No offense, but they’re not stamped engineers.”
He added that he doesn’t believe the issues would be fixed by another task force meeting, either.
“With every public task force, committee or commission, your aim is to have public buy-in, public acceptance,” he said. “But you don’t want it at the risk of putting forth bad policy or policy that could make flooding worse, as we fear in some of these changes as of right now.”
For example, Arnold said, the city is proposing an increase to the peaking factor, or the ratio of peak hourly water flow to average daily flow. Though in some areas of the city it may alleviate flooding, Arnold said, engineers fear that it could make flooding worse in some areas.
“Just because you make a storm system wider … does not necessarily mean it’s going to net less flooding,” he said. “In fact, it could be concentrating water where it shouldn’t be.”
Others say the city needs the manual in place as soon as possible. Susan Lyons, chairwoman of flood mitigation advocacy group Groundswell, said this is a step in the right direction for Charleston.
“This document is a tangible effort on the part of the stormwater department to really put boundaries around what’s possible now and to begin to look at development and redevelopment first through the lens of flooding and sea rise,” she said.
Lyons said she’s heard the opposition from builders and engineers and said it’s “a shame” that they’re resisting.
“The water is high, and if we don’t move quickly, we’ll have no chance of containing and protecting certainly the peninsula and specific portions of the outer areas of the city,” she said. “So I’m excited that they’ve done this. I hope to heck they don’t … defer and mess around with it and try to water it down, because it’s really important that we get tough.”
This story originally appeared in the Feb. 10, 2020, print edition of the Charleston Regional Business Journal.a