Nantucket advisory committee hears detailed Easy Street flood-mitigation update; design options, costs and outreach planned

Leah Hill, the town’s Coastal Resilience coordinator, briefed the Coastal Advisory Committee on Feb. 10 about the Easy Street flood-mitigation project and the next steps toward design and permitting. She said work funded under a CZM grant that concluded in June 2025 produced an existing-conditions and flood-risk assessment, three concept designs and a preliminary feasibility report.

Hill said the project team used the Massachusetts Coast Flood Risk Model (MCFRM) to map tidal flooding time horizons and has chosen a conservative design-flood elevation (8.0 ft NAVD88) for the most protective alternative “because this [is] critical infrastructure, we can’t get this wrong.” She described three concept alternatives — bulkhead expansion and elevation; an adaptable road-raising that would initially raise the road to about 6.5 ft NAVD88 with capacity for later adaptation to 8 ft; and a straight road-raising to 8 ft — and stressed tradeoffs between near-term cost and long-term protection.

On costs, Hill presented AACE Class 4 concept estimates and emphasized uncertainty at the 10%–level design stage. She cited an example: “for the bulkhead expansion and elevation that estimate is about 47,000,000. If we wait until 2028 to construct it then that'll go up to about 53,000,000.” She also noted a no-action cumulative-loss estimate from the risk assessment: “if we…take no action we can expect a cumulative loss of 1,200,000,000.”

Hill described the multi-task scope moving forward: Task 1 to fill data gaps (including a protocol to integrate local NOAA tide-gauge records into design flood elevations); Task 2 to expand public outreach and stakeholder-focused engagement; Task 3 to carry out field investigations (environmental delineations, geotechnical work and groundwater monitoring, updated traffic counts and routing for construction); and Task 4 to produce bid-ready design and permitting packages. She said permitting timelines are uncertain — ranging from roughly 18 months to 5–7 years — while construction is estimated at about two years (with seasonal moratoria on downtown work).

The committee questioned model integration, stakeholder identification and timing. Doug Rose asked whether coastal, stormwater and groundwater models can be combined; Hill said firms are discussing ways to overlay models to assess compound-event impacts. Several members pressed how private-property impacts (driveways, utilities, historic structures) will be addressed; Hill said the project will produce photo-realistic graphics and rely on a Resilient Nantucket addendum and the historic-structures review to guide property owners and clarify recommended elevations.

On coordination with other island projects, members repeatedly raised the Steamship Authority terminal’s future plans. Hill said the Authority participated in earlier grant and design meetings but had not chosen a preferred alternative; she added that “whatever the town does for Easy Street needs to be able to be tied in to whatever the Steamship [Authority] does” and that the three design options were developed with tie-in potential.

Hill warned of the risks of pausing the project: “If we pause the project we risk losing that momentum and grant competitiveness,” she said, adding that delays increase the chance of emergency repairs that are often more expensive and less effective. She told members funding is in place to continue design and permitting (Annual Town Meeting funding from 2025) but construction money is not yet secured.

Next steps: Hill said staff will present the project to the Select Board at its Feb. 18 pending-contracts meeting, continue the CRP-related implementation work, complete the tide-gauge protocol and FEMA benefit-cost analysis, and advance stakeholder outreach. Committee members asked staff to continue producing accessible visual materials and to share data maps showing affected private properties.