EVERETT — The cost of building a new dike to help restore tidal marshes on Smith Island is expected to cost Snohomish County $1.2 million more than originally thought.
The salmon-habitat project is set to wrap up next summer at an overall cost of $28 million. That’s when a contractor would breach old dikes, allowing about 350 acres of low-lying farmland to flood.
“The bottom line is that we’re still within budget,” public works director Steve Thomsen told the County Council on Tuesday.
Thomsen said the project remains within budget because the original bid for the dike work came in lower than expected.
The council voted 5-0 Wednesday to authorize Executive Dave Somers to sign the change order for the additional amount.
The change order adds to the original $12.3 million bid the county awarded in 2015 to Scarsella Brothers, a Kent-based construction company.
About three-quarters of the extra cost owes to the additional material needed to compensate for the dike settling, Thomsen said. The other quarter of the cost is for work done last winter to control erosion.
“We’re building a mile-long dike with a very long footprint and a lot of material,” he said. “It’s on very deep, compressible soils.”
The Smith Island project stems from the federal government’s 1999 listing of Puget Sound chinook salmon as threatened under the Endangered Species Act. It’s intended to increase survival rates for juvenile chinook salmon. The area that would be flooded sits just east of I-5, bounded by Union Slough and Everett’s wastewater lagoons.
The habitat is expected to regenerate gradually, over several years.
Settlers began diking the salt marshes on Smith Island around the time of the Civil War. The island’s name comes from Dr. Henry Smith, who arrived at the mouth of the Snohomish River in the early 1860s. He and other pioneers envisioned turning the area into a “New Holland,” according to an article on History link.org.
Only about a sixth of the Snohomish delta remains intact. The rest has been altered.