New Hampshire approves $2.8M for tidal culvert replacements

July 6, 2023
New Hampshire approved NOAA funding to replace three undersized tidal culverts on state roads, enhancing flood resilience and local ecosystem health.

The New Hampshire Department of Environmental Services (NHDES) that the Governor and Executive Council recently approved $2,876,442 of grant funding from the National Oceanic and Atmospheric Administration (NOAA) that will enable the New Hampshire Department of Transportation (NHDOT) to replace three undersized tidal culverts on State roads in the Towns of Stratham and Rye, New Hampshire.

The selected projects were identified by the NH Resilient Tidal Crossings Project as the highest priority tidal crossings for replacement based on a coast-wide field assessment and prioritization process that evaluated 120 tidal stream crossings in 2018 for ecosystem compatibility, flood resilience and structure condition.

In 2019, a unique partnership between NHDES Coastal Program and NHDOT was initiated and facilitated by The Nature Conservancy (TNC) to advance a “pipeline” of high priority culvert replacement projects. With grant funding from the National Fish and Wildlife Foundation- National Coastal Resilience Fund and NOAA, the team worked with engineering consultant, CMA Engineers, to conduct alternative analysis, design, engineering, and permitting at three of the highest priority state-owned tidal crossing sites. The tidal culvert design process followed the “New Hampshire Coastal Flood Risk Summary, Part II: Guidance for Using Scientific Projections” and adhered to new NHDES permitting rules that are specific to tidal culvert replacement.

“By considering the New Hampshire Coastal Flood Risk Guidance early in the planning process, the Projects incorporated coastal resilience principals into the design by identifying project goals, the design life of the project, and the project’s tolerance to flood risk from increases in sea level, coastal storms, and extreme precipitation.” says Kevin Lucey, Habitat Coordinator for the NHDES Coastal Program.

‘Right sizing’ tidal culverts not only mitigates flood risk, but it can also restore the functions that sustain healthy and thriving coastal habitats.

The design goals for these projects are to replace aging infrastructure with crossing structures that minimizes future flood risk, eliminate tidal restrictions, enable upstream marsh migration, and benefit organism passage and wildlife habitat. Construction is planned for 2025.

The funded replacements are as follows:

  • Squamscott Road at Chapman’s Landing Salt Marsh
    Squamscott Road is local connector between Route 33 and Route 108 in Stratham. Within a 0.3 mile segment, Squamscott Road crosses three separate wetland tributaries of the Chapman’s Landing Salt Marsh.
    The project in Stratham will restore tidal wetlands by replacing two tidal culverts along Squamscott Road as part of a single construction project. At each site, the existing 18-inch round pipes will be replaced with 8 ft wide x 7 ft high concrete box culverts.
  • NH Route 1A at Awcomin Salt Marsh, Rye Harbor
    NH Route 1A is a vital north south transportation corridor on the immediate coast and is the primary access to New Hampshire’s most popular beaches, tourist amenities, active working waterfronts, as well as tourist lodging, local businesses, and residential neighborhoods.
    The selected alternative at Route 1A at Rye Harbor will replace the existing 3.5 ft wide x 7 ft high granite block culvert with a 15 ft wide x 7 ft high, 3-sided concrete box on footings.

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