FAIRBANKS — Officials in Fairbanks hope erosion along the Chena River can be tamed by using an abundant local resource — root wads of spruce trees.
Using a technique developed by the U.S. Fish and Wildlife Service, landscape contractor Great Northwest Inc. last week “planted’ 42 white spruce root wads in a 200-foot section of the Chena behind the Fairbanks North Star Borough Building.
The connected root wads form a foundation that resembles a crib. Filled in with rock, gravel and topsoil, the configuration is designed to grow into a vegetative mat that will hold the bank in place, the Fairbanks Daily News-Miner reported.
“It all becomes one entity tied together,” said landscape architect Gordon Schlosser of Great Northwest. “It’s not rocket science; it’s common sense if you spend any time in the woods and look at riverbanks that are solid.”
The Fish and Wildlife Service has been using root wads for stabilizing Kenai River banks for more than 10 years, said Julie Jones, director of Festival Fairbanks.
“They’re finding it to be quite successful, especially as far as maintaining fish habitat,” she said. “It’s just a great technology.
“The old days of throwing junk cars, old concrete and rocks on the riverbank may become a thing of the past,” Jones said.
The service awarded a $66,000 grant to Festival Fairbanks for the project. The borough added $33,000.
The technique starts with a log placed in a trench in the river. It acts as a footing.
Root wads are excavated with 8- to 10-foot trunks attached. The trunks are placed perpendicular to the river with root wads running parallel to the water.
A “header” log is placed on top of the tree trunks. The contractor then drives a metal rod through the header, the log of the tree with roots and the footer log to pin everything in place.
The crib that forms is filled with rock and gravel and finally topsoil and cuttings of fast-growing willow.
Borough offices were built in the early 1980s. Deep-rooted plants were removed and replaced with grass, Jones said.
“There were a lot of cracks going up the riverbank, and the vegetative mat was hanging over the bank,” Jones said. “When boats come by, the water from the wake slips up under the vegetative mat, and the soil starts to wash away.”
River bank stabilization is part of Festival Fairbanks’ plan to build a foot path on the north side of the Chena. The organization is trying to raise $5 million for the project, Jones said.
Great Northwest harvested root wads from property it owns, Schlosser said.