$2.9 million awarded to NH Resilient Tidal Crossings Project

Concord, NH – The New Hampshire Department of Environmental Services (NHDES) announced today 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. Lucey further described how the design process showed that ‘right sizing’ tidal culverts not only mitigates flood risk, but it can also restore the functions that sustain healthy and thriving coastal habitats.
“New Hampshire has aging infrastructure that needs to be addressed, and the species passage and tidal wetland improvement is recognized as an important function of those replacements”, said William Oldenburg, Director of Project Development from NHDOT.  

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.

Squamscott Road at Chapman’s Landing Salt Marsh, Stratham, N.H.
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, Rye N.H.
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.

Background:
There are approximately 120 tidal stream crossings in New Hampshire. A tidal crossing is a culvert, bridge, or tide gate associated with a road or other form of crossing infrastructure that conveys tidal flow or is located at the head of tide. There are relatively few tidal crossings in NH when compared to estimated 21,000 freshwater crossings in the state, but they play a critical role for the ecological integrity of aquatic systems.  These crossings often restrict tidal flows which alters hydrology, sediment movement, salinity, and plant species composition of tidal marshes. Tidal restrictions ultimately affect the ability for salt marsh systems to build in elevation and migrate upstream with rising sea levels. Tidal crossings can also block migratory fish from accessing critical upstream habitats. From a community resiliency perspective, tidal crossings are necessary to safely and reliably convey people, goods and services throughout coastal communities; however, this infrastructure is increasingly at risk from flooding and erosion with rising sea levels and more frequent and intense storm events.

The NOAA grant funding for this project comes from the Bipartisan Infrastructure Law through the “Coastal Zone Management (CZM) Habitat Protection and Restoration Infrastructure Investment and Jobs Act” grant program.

For more information, please contact Kevin Lucey, NHDES Coastal Program Habitat Coordinator, at kevin.p.lucey@des.nh.gov and (603) 559-0026.