Zis a ba Estuary Restoration

Excavators and Archaeologist during construction observation for artifacts

Cardno is proud to be supporting the Stillaguamish Tribe’s work to restore functioning ecosystems that support expanded treaty fishing and hunting opportunities at ‘zis a ba’.

The Tribe aimed to restore the land to tidal influence and thereby reinstate habitats for Stillaguamish Chinook populations, which had been listed under the Endangered Species Act (ESA).

Cardno was engaged by Stillaguamish Tribe Natural Resources Department to provide strategic support across assessment, permitting and compliance, cultural resources support, environmental management and restoration tasks.

A team of 20 Cardno engineers, cultural resources experts, and scientists worked with the Stillaguamish Tribe to support the restoration of riverine and tidal process to nearly 100 acres of diked former tidal marsh.

To help deliver this project, our team performed the following key elements:

  • designed and built a new setback dike to protect agricultural lands and other infrastructure, including a habitat berm that protects a pipeline and a large one-way floodgate to improve flood drainage for the adjacent 4000 acres of farmland
  • constructed seven dike breaches to connect new dendritic tidal channels
  • created mudflats, intertidal and high salt marsh habitat.

As a result of this work, Cardno provided estuary rearing habitat for the threatened Chinook salmon and steelhead as well as provided nursery habitat for Dungeness crabs and other fish, waterfowl and wildlife.

The restoration work and setback levee improved habitat and water quality by allowing the estuary to function more naturally and encouraged increased habitat complexity by establishing 4.5 acres and 3 miles of tidal channels by 2025.