Town Council considering proposed stormwater text amendments


By Adam Powell

At Wednesday night’s Chapel Hill Town Council meeting, the board opened a legislative hearing to consider new land use management ordinance (LUMO) text amendments to the town’s stormwater management requirements.

Sue Burke, the town’s Stormwater Management Engineer, presented three text amendments to the stormwater management criteria in its LUMO.

Burke presented a timeline for the various LUMO stormwater-related text amendments, indicating that the process began back in the summer of 2021 with a petition from a council member.

From there, the town began a Booker Creek Working Group report in the summer of 2023, leading to another council member petition in November of this past year.

Following a series of public information meetings held by the Chapel Hill Planning Commission and the town’s Stormwater Management Utility Advisory Board in February, the town was ready to move ahead with the legislative hearing.

Burke indicated that in 2022, the town contracted with the consulting team of Skidmore, Owings, and Merrill, a Chicago-based architectural and engineering firm, and the SRF Consulting Group to conduct a review of the Town of Chapel Hill’s stormwater regulations. That particular report was completed in April 2023.

Burke explained that the report recommended adding the 100-year, 24-hour storm event to the peak rate requirement and clarifying the runoff volume for the water quality requirement.

“There was concern that the stormwater management regulations adopted in 2004 did not address the increased precipitation intensity and frequency that was being experienced as part of climate change,” Burke said.

“Finally, at the Nov. 29, 2023 council meeting, a council member petition was presented, which included a request that the 100-year storm be added to the regulations as soon as possible,” Burke told the town officials. “In February, town staff hosted two public information meetings, and I also presented the text amendments to the Planning Commission and the Stormwater Advisory Board. Both the Planning Commission and the Stormwater Advisory Board unanimously recommended approval of the text amendments.”

“The changes that are being proposed by these text amendments are the minimum needed to respond to the council member petitions,” Burke added. “The SRF report and the Booker Creek Working Group recommend more comprehensive revisions to the stormwater management regulations, which would be part of the larger LUMO rewriting initiative.

Burke explained that a so-called 25-year storm or 100-year storm is based on the annual probability of a major weather event’s potential occurrence.

“[It] is the probability that it will occur in any given year,” she said. “So a 25-year storm would have a 4 percent chance of occurring in any given year. And the 100-year would have roughly a 1 percent chance of occurring in a single year. So, because it’s probabilities, then you know you can have potentially back-to-back 100-year storms.”

Burke went into specifics about the three text amendments, which included two clarifications and one addition, contained in Article Five, Section 5.4, Subsection 5.4.6 of the town’s LUMO. The proposed amendments clarify that the section applies to new developments and redevelopments that increase impervious surfaces while also clarifying the water quality volume to be treated by town staff. In addition, the amendments add the 100-year, 24-hour major storm event to the peak rate requirement.

“The first two are clarifications,” Burke explained. “One clarifies that the rules apply to new development and redevelopment. There’s [also] a net increase of impervious surface. The third one adds the 100-year, 24-hour storm to the peak rate requirement. Right now the peak rate requirement requires an applicant to ensure that the peak rate of runoff leaving a project site after development does not exceed the peak runoff rate before the project was developed. And that’s for the one-year, the two-year and the 25-year storms. And so this would add the 100 years to that.”

Burke recommended the town officials open the legislative hearing, receive public comments and provide feedback to Burke and other involved town staff, and then continue the legislative hearing to May 1.

Mayor pro tem Amy Ryan asked whether or not the next LUMO text amendment standards would impact smaller projects around town. Her concern was that additional standards would make some potential projects too cumbersome or burdensome to take part in.

“I know that what you do is very complicated. And I don’t want to put you on the spot for tonight,” Ryan said to Burke. “But when you come back, could we address and see maybe if there’s something that we need to do to not put impossible or very onerous burdens on our smaller redevelopment projects.”

“Any projects that are being proposed on sites that already contain impervious surfaces, like a redevelopment project, if there’s no net increase, these rules would not apply,” Burke said in response to Ryan. “And even if there is a small amount of increase, it’s only going to apply an incremental increase.”

“I’d really like to see if there’s a way that we could nuance these regulations for the smaller properties,” Ryan added. “We’re doing more infill. We’re doing densification. There may be lots that have never developed that will be developing in the future. So if we could just figure out a way either to exempt smaller properties or give credit for things like retaining mature tree canopy or using permeable pavement. But just to figure out a way that we’re not keeping these smaller projects from developing because of these regulations, that would be great.”

Addressing Ryan’s concerns, town staff indicated that the proposed changes were specifically meant to address some of the concerns about cumbersome regulations raised in previous petitions, and that the town would have an opportunity in the coming weeks and months to make additional changes to the stormwater regulations in the larger LUMO rewrite.

Council Member Elizabeth Sharp requested clarification on the impervious surface changes, asking how town staff would apply falling rainwater, and the runoff created from that rainwater, to new regulations and limitations.

“Local governments can only regulate the increase in impervious surface for a redevelopment project,” Burke said. “It can’t retroactively require the entire site to be controlled. The rainfall amount gives you a volume.”

The council ultimately unanimously voted to continue the public hearing until May 1, at which time they will receive more information about the LUMO rewrite, as well as some of the nuances for smaller projects requested by Council Member Ryan.

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