Mat-Su finishes Fern Street rebuild with new Cottonwood Creek fish culvert

The Mat-Su Borough said Wednesday it has finished rebuilding Fern Street from Knik-Goose Bay Road to Mint Drive, replacing a Cottonwood Creek crossing that had blocked salmon from most of the creek's watershed.

The old crossing was three arch culverts. The Mat-Su Salmon Partnership, a group formed in 2005 to protect salmon habitat in the Mat-Su, called it the lowest remaining barrier on the creek, the first one fish reach heading upstream, and said it blocked 71% of the watershed. It was a barrier to both adult and young salmon. Cottonwood Creek has Chinook, coho and sockeye.

Replacing it would improve passage to more than 8.2 miles of stream and 659 acres of lakes upstream, the partnership said, and let young salmon move freely downstream to places where they grow and spend the winter.

In its place, the construction contract called for a steel box culvert about 25 feet wide and 8 feet tall, with stream gravel, bank fill and live willow stakes along the creek. Crews had until July 15 to finish work in the water.

The road needed the work, too. Since 2014, Fern Street has gone from a residential access road to a major route between Knik-Goose Bay Road and Fairview Loop, with far more traffic than it was built for, a borough memo said in April. Poor drainage, frost-susceptible soils and restricted sight distances led to frequent pavement failures and safety hazards, the memo said. The rebuild added a pathway along the west side.

Tutka LLC, the lowest of eight bidders, got the $1.9 million construction contract in April, about $520,000 of it for the creek crossing. A 2024 borough mailer said the project is funded by a road program voters approved in 2021. The fish work also has a salmon grant through the Alaska Department of Fish and Game and matching money from the City of Wasilla.

It's the latest in a long line of culvert swaps. The borough has been fixing fish-blocking culverts since 2001 and said it had made more than 100 passable by 2021.

The borough is also lining up another fix in the same drainage, at the outlet of Anderson and Hart Lake on Charley Drive, where a culvert blocks coho. In September the Assembly accepted a $45,000 U.S. Fish and Wildlife Service grant toward replacing it, with $105,000 in borough matching money. That would restore access to nearly a mile of stream and about 214 acres of lake habitat, according to a borough memo.

At that meeting, Rod Hanson told the Assembly he had recently joined a field visit where a pike barrier had been installed on Cottonwood Creek to keep pike out of Anderson Lake. A salmon was trying to get into the lake while they were there, he said, and there were "buckets full of" young salmon being helped over the weir.

The borough plans to carry the upgrade north to Fairview Loop, making Fern Street a north-south collector route. That second phase depends on funding and right-of-way. The same mailer estimated $13.5 million for both phases.