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Prime Hook National Wildlife Refuge Restoration

Milton, DE 19968, USA
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Atkins
Contact Partner

Goverment Champion

U.S. Army Corps of Engineers (USACE) - not local government

Cost

Initial:
19.8 Million USD

Project Status

Operational since 2016

Keywords

Restoration
Hurricane Sandy
mitigation
marsh habitat

Challenges Addressed

Flooding
Coastal & Tidal Flooding
Hurricanes & Severe Storms
Systemic Stressors
Ecosystem Degradation
Natural Disasters

Motivation

Resilient city
Sustainable city

Funding / Financing

Federal grants

Project Type

Project

At a Glance

After Hurricane Sandy severely damaged the Prime Hook National Wildlife Refuge, rather than repair and maintain the refuge in its existing form (an artificial freshwater habitat), the U.S. Fish & Wildlife Service determined the best solution was to return the habitat back to its original state as a salt/brackish marsh.

Problem Addressed

Before active management, the refuge was diked and managed into four freshwater impoundments that cover more than 10,000 acres. After being severely damaged by a series of storms, including Hurricane Sandy, the Prime Hook National Wildlife Refuge—a protected and critical sanctuary for migratory birds—required restoration and mitigation from the impacts of rising sea levels. The refuge and its adjacent water bodies are a key stopover site for migratory birds moving through the region and western Delaware Bay. It is also home to many threatened and endangered species.

USACE used/is using Atkins design & engineering services to address this/these challenge(s).

Solution(s) Used

Atkins provided restoration and mitigation to the refuge and helped return it to its original state as a salt/brackish marsh after the habitat had been severely damaged by a series of storms. In addition to restoring habitat, the broader goal is to restore natural water flow, repair breaks in the existing dunes and create a marsh and beach more resilient in coastal storms. The Prime Hook tidal marsh restoration project has been the largest of its kind ever on the east coast of the United States. Over 15-months, construction included: a dune, beach, and back-barrier beach platform along nearly 8,000 feet of shoreline, restoration of 9-foot dune with a 100- to 600-foot-wide back barrier platform extending into the marsh, plantings and 10,000 feet of fencing have been installed to stabilize the area, dredging of more than 25 miles of tidal channels to restore flow, removal of several man-made water-control structures. All of which was done to revert the area back to a saltwater marsh with some areas of fresher or brackish wetlands.

To identify sustainable solutions, Atkins generated a hydrodynamic and numerical model of the refuge and the adjacent bay region using Delft3D modeling software to account for the effects of tides, wind, waves, and the mixing of fresh and salt water. Their combination of technical, scientific, and industry experts conceived a design that incorporated existing features with new ones in a way that balanced theory and constructability.

This project led to the creation of an established Atkins model for habitat restoration and flood-proofing for coastal developments facing sea level rise. By incorporating sustainable design into natural and manmade features, such as conveyance channels, this model is a “next-step” approach to basic marsh-fill designs and may provide resource benefits to recent re-nourishment projects along the gulf coast. The refuge’s design serves as a model for effective management of coastal erosion from sea level rise—applicable to many other areas along the U.S. coastline.

Something Unique

The project received the 2016 Environmental Excellence Silver Award from the World Organization of Dredging Associations (WODA) in its environmental dredging category.

Who Should Consider?

Communities looking to restore coastal habitats.

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