Mount Pleasant officials outline new ordinance and GIS tool to protect isolated wetlands

Mount Pleasant officials on a county advisory panel described a newly adopted ordinance and an accompanying GIS screening tool designed to identify and protect isolated wetlands that fall outside federal Clean Water Act protections after a 2023 Supreme Court ruling.

Kevin Mitchell, deputy director of Engineering Development Services for the Town of Mount Pleasant, told the committee the town adopted the ordinance on April 14 after about eight to nine months of public meetings and reviews. He said the ordinance closes a regulatory gap created by the 2023 decision narrowing which waters receive federal protection, and applies to isolated wetlands associated with subdivisions, non‑residential projects and single‑family activity.

“Our charge was to close the gap that was created in 2023 with the Supreme Court ruling that redefined waters of the U.S.,” Mitchell said. He described the ordinance’s application in Mount Pleasant’s land development regulations rather than zoning code and said it requires wetland delineations prepared by scientists with at least five years’ field experience using the U.S. Army Corps of Engineers manual and the Southeast supplemental data sheet.

Mitchell described buffer guidance built into the ordinance as intentionally flexible: the town set an average minimum buffer of roughly 5–20 feet to balance private property rights and resource protection, but the planning commission can require wider buffers — double or triple the minimum — for larger parcels. He also listed exemptions, including boundary surveys and emergency critical‑infrastructure work, town‑approved capital projects, and parcels under certain acreage thresholds that show no indicators of wetlands on the town’s mapping tool.

Mave Gimbert, Mount Pleasant’s resiliency manager, demonstrated the town’s GIS screening tool, which combines three data layers — the National Wetlands Inventory (NWI), hydric soil mapping from the Natural Resources Conservation Service, and a depressional/sink analysis using recent topography — to identify parcels for closer review. Gimbert said areas where two of the three indicators overlap are treated as likely wetland locations and trigger requests for professional delineations; areas with all three indicators have higher confidence.

“We start with NWI, hydric soils and depressional features, and where those overlap we flag the parcel for further review and, where appropriate, recommend an on‑the‑ground delineation,” Gimbert said. She added that the town follows up with drive‑by site checks and other overlays (for example, town drainage ditches) to reduce false positives before requesting a delineation from an applicant.

During questions from county planning staff, Mitchell said he had reached out to local consultants and was given a ballpark figure of about $1,500 for an initial wetland delineation, though he emphasized costs could increase depending on field work and site complexity. “It depends on the situation and how much field work is involved,” he said. “$1,500 would be a starting estimate from a local practitioner.”

Mount Pleasant staff said their mapping tool is built for town boundaries but can be expanded to countywide layers and offered to share the ordinance and presentation with county planning staff to support regional coordination. County staff on the call noted that stormwater/MS4 screening already uses NWI and other resources, but that the town’s ordinance and tool address a newly visible regulatory gap for non‑jurisdictional wetlands.

Next steps discussed included a potential county survey of municipal approaches to isolated wetlands, sharing Mount Pleasant’s ordinance and mapping tool, and evaluating whether a countywide or interjurisdictional approach is warranted.

The town’s approach emphasizes early screening in feasibility and single‑family permit reviews and puts the burden of proof on property owners to hire qualified professionals when staff screening indicates possible wetlands. Mount Pleasant staff said the process is early in implementation: feasibility meetings and single‑family checks have returned several flagged sites, but the town had received few formal delineations back as of the presentation.

The county planning representative who asked about costs said the estimate would help municipalities and residents evaluate compliance burdens. Mount Pleasant staff offered to meet with county planning to walk through the ordinance and mapping tool in more detail.

The committee discussion closed with agreement to explore regional information‑sharing and coordination to avoid a patchwork of municipal rules.

Ending: Mount Pleasant staff said they will provide the ordinance and the mapping tool to county staff; county planners proposed surveying other municipalities to evaluate whether a coordinated countywide approach is feasible.