Committee reviews three Easy Street flood‑mitigation concepts; staff to synthesize public input for select board

Leah Hill, project manager for the Town of Nantucket, presented the feasibility and design options for the Easy Street Flood Mitigation Project during the Coastal Resilience Advisory Committee meeting on March 25, 2025.

Hill described three primary alternatives under study: (1) rebuild and elevate the waterfront bulkhead, adding tiebacks and localized road elevations/speed‑humps to isolate downtown low points; (2) an adaptable road‑raising to 6.5 feet NAVD88 with the option to raise later to higher levels; and (3) full road‑raising to 8.0 feet NAVD88 to reach a longer‑term design elevation. She emphasized the project is intended to reduce flood risk, not eliminate it, and that the effort is funded in part by a 2024 Coastal Zone Management (CZM) grant with deliverables due in June 2025.

Hill said the project team includes town staff and Arcadis consultants; subconsultants were listed for engineering and design. She noted the Easy Street watershed is roughly 53 acres of mostly impervious upland that directs stormwater downslope into the downtown pocket, and that stormwater runoff plus tidal inundation together drive the most severe local events. Hill said each alternative would require upgrades to stormwater infrastructure and a pump station to move accumulated water out of the pocket.

Key technical details Hill cited: the lowest existing road surface at Easy Street is about 2.5 feet (NAVD88), the existing bulkhead is about 6 feet, the adaptable road‑raising alternative is designed to 6.5 ft NAVD88 (a level tied to the 2050 mean‑higher‑high‑water projection used in modeling), and the full road‑raise alternative to 8 ft NAVD88 is intended to provide protection farther into the century. She said mean higher high water today is roughly 1.5 feet at the tide station datum and noted that datum changes by NOAA and geodetic updates will need to be tracked for long‑term reference.

Committee members asked technical and process questions and offered preferences. Some points raised:

- Several members — including Joanna Roach and Gary Beller — argued for higher or more definitive action so private property owners and businesses can plan for longer‑term adaptation. Roach said the 8‑foot option would give clearer direction to downtown businesses and institutions.

- Others — including Sarah Boyce and Bill (Arcadis) proponents in the discussion — favored the adaptable 6.5‑ft option as a more politically and financially achievable first step that still addresses groundwater impacts and preserves the option to elevate later.

- Members repeatedly asked how utilities and buried infrastructure would be handled; Vince Murphy (town staff) said utilities and stormwater mains may need relocation or raising and that further engineering is part of later design stages.

- Committee members emphasized coordination with the Steamship Authority and Nantucket Yacht Club. Hill said staff have met with the Steamship Authority and will coordinate design so there are no seams between their terminal work and the town project.

- Concerns about groundwater and subsurface seepage were raised for bulkhead options; Hill confirmed a bulkhead‑only approach does not address groundwater table rise and groundwater effects would need separate measures.

- Several members urged the town to clarify implementation pathways and the likely impacts on private driveways and access; Hill said those details, including cost sharing or betterment approaches for private tie‑ins, would be examined during 30% design.

No formal committee vote was taken on a preferred alternative. Hill said staff will compile the committee’s feedback and the public comments collected at two recent virtual open houses (roughly 60 participants at the morning session and 30 at the evening session) and present a staff recommendation to the Select Board. The grant work plan requires a preferred alternative and 30% design materials by the end of the CZM grant period in June 2025.

Why it matters: Easy Street provides emergency and commercial access to the Steamship Authority terminal and downtown businesses; members repeatedly characterized the corridor as a high priority for early implementation. Committee members also urged that stormwater routing and upstream detention measures be pursued in parallel so upgrades at Easy Street are not overwhelmed by upland runoff.