Herring River Salt Marsh Restoration and Green Infrastructure Improvements

The Herring River Estuary was a great salt-water tidal marsh flowing into and out of Cape Cod Bay. In 1909, the Herring River was diked in the hopes of providing relief to vacationers from pesky mosquitos breeding in the salt marsh (tourism being critical to the region’s economy). Unfortunately, significantly reducing the tides and exchanging water within the estuary upset the health of this sensitive ecosystem. Some of these changes resulted in reduced oxygen levels and increased acidity in the water, causing significant harm to the habitat of fish and crustaceans. Fresh water plants and species invaded the ecosystem, replacing native marine plants that formerly thrived over large areas. Almost all aquatic life in the estuary suffered the effects of diminished water quality. The numbers of migrating fish were significantly diminished and the wetlands remain, to this day, affected by restricted tidal flows.

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Solution

The Herring River Restoration Committee (led by MA DER, NOAA, NPS, and USFWS) and Conservation Law Foundation selected Fuss & O’Neill to lead the design of a $15 million green infrastructure project of a new bridge structure and two secondary dike structures across Mill Creek. The purpose of this project is to replace an existing causeway with a bridge structure to allow gradual restoration of tidal flows to restore 1,100 acres of former salt marsh. The new bridge over the Herring River will also provide ADA compliant public boat and fishing access improvements for the public.

Design

A major element of this project is to develop a bridge structure with a 160-foot span at the mouth of a coastal river in a manner that allows National Park Service scientists to control flows into the marsh system and provides future flood protection for homes and infrastructure around the restored marsh area. As a result, the bridge design is one of a kind and includes removable flood panels that can be inserted through the bridge as well as slide gates in some of those panels to provide more finite controls.

Concepts were developed that allowed accurate assessments to identify which configuration would best meet the project’s unique functional requirements while minimizing impacts to adjacent natural resources, regulatory barriers, construction costs, and long-term operating and maintenance costs. Carefully prepared reports, alternatives assessments, and cost/impact evaluations documented efforts through all phases off the feasibility studies. These reports were prepared in a manner to facilitate inclusion into later permitting and regulatory compliance filings.

Practice Areas Involved

Collaboration

Workshops were conducted with stakeholders, project partners, and the public to present and discuss alternative bridge configurations and public access improvements. This workshop approach allowed the design team to review alternatives and to obtain critical feedback that allowed, thus refining the configurations and evaluating costs, impacts, and benefits.