Town and engineer outline constructed-wetland plan to treat stormwater at Kohala outfall

Town principal environmental analyst Melissa McCarron presented final designs May 15 for an "end-of-pipe" constructed wetland at the Kohala outfall intended to treat stormwater before it reaches Georgia Pond. She said the 1930s stormwater pipe runs roughly 7,300 feet by gravity to the pond and delivers nutrients, sediment and bacteria that have contributed to macroalgae and blue-green algae blooms.

"Our overall goal is to keep the character of the site at the end of Kohala Road while incorporating water-quality improvements for the benefit of Georgia Pond," Melissa McCarron said. Project engineer Ryan Winter of BHB walked trustees through the design elements: relocating the primary outfall closer to Georgia Road, creating a linear constructed wetland with sediment basins and a micro-pool, and using native low- and high-marsh plantings to provide treatment and infiltration before water reaches the pond.

The design preserves the existing maintenance access, adds a sediment-trap basin and a secondary micro-pool behind a small berm to increase infiltration, and retains the existing outfall as an overflow for large storm events. Winter said the system is intended to capture the watershed''s "first flush" (the initial runoff that carries the largest pollutant loads) and that the configuration is sized to handle roughly the first one inch to one and a half inches of rainfall from the current watershed.

The presenters said permitting is the immediate next step: the U.S. Army Corps permit has been secured, the DEC comment period closed May 14 and the town is awaiting DEC''s final determination. If DEC issues the permit without substantive conditions, the town anticipates completing construction documents and going to bid, with construction likely in 2027 after the summer season.

Trustees asked about noise and parking. Winter replied there will be no new mechanical equipment or active facilities at the site, so the project is not expected to increase noise. On informal parking at the cove, project staff said they plan visual and physical protections (larger decorative rocks rather than formalized pavement or lots) to discourage vehicle intrusion into the wetland; specific signage or parking management was discussed as a separate village decision.

McCarron and Winter emphasized monitoring and maintenance: the contractor will be responsible for a five-year establishment and monitoring period built into the contract, including management of Phragmites and additional plantings if necessary. Longer-term monitoring and Phragmites control beyond the initial establishment period would require DEC agreement and likely additional funding through the town''s Community Preservation Fund (CPF) or subsequent village applications.

The presentation named coordination with multiple stakeholders, including the village of East Hampton (property owner), the town trustees, the village planner and Friends of Georgia Pond. The project was developed from a 2016 water-quality improvement plan and subsequent engineering review; the town said the final design reflects iterative technical review and stakeholder input.

The board did not take a formal vote on the project at the meeting; presenters said they would return with bidding documents once DEC permits are resolved.