The state Department of Transportation this week said it would pursue “vegetated river protrusions” as part of mitigation for the Haines Highway improvement project, an apparent response to concerns that two miles of planned rock embankments would degrade roadside fish habitat between 3 Mile and 25 Mile.

DOT spokesman Jeremy Woodrow said the revised plan grew out of recent discussions with transportation and tribal officials in Klukwan, where an “engineered log jam” has been used for 10 years to stabilize a bank and create riverside habitat friendly to fish.

“This is a success story. It’s why we work with the public and governments before going ahead with projects, to respond to concerns and meet everybody’s expectations,” Woodrow said.

Klukwan village president Jones Hotch Jr. this week said he’d reserve comment on the protrusions plan until seeing a proposal on paper. He said he’s been “extremely happy” with the village’s logjam embankment, which protects its new heritage center and cultural camp from erosive effects of the Tsirku and Klehini rivers, which converge there.

The Upper Lynn Canal Fish and Game Advisory Committee last week addressed a letter to DOT, asking it specifically to create engineered log jams to improve habitat for rearing king salmon.

“The current (environmental plan) includes plans for linear riprap (rock), a poor choice as it can be detrimental to fish habitat and should be avoided if at all possible,” the committee wrote.

Ben Kirkpatrick, a former state Fish and Game habitat biologist who worked on the Klukwan logjam project, testified to the committee last month that rock “riprap” accelerates riverbank currents, while the logjams slow currents and create shelter for rearing king and coho salmon.

DOT’s decision doesn’t go as far as Kirkpatrick wanted, but it may produce similar results.

Woodrow said the state’s plans for protrusions won’t replace riprap or use logs to create an embankment, but will be built between riprap and the river. “Engineered log jam technology will be employed but not as a slope stabilization method.”

Engineered logjams, while used in the Lower 48 and at some locations in Alaska, haven’t been proven to work for protecting roadbeds in Alaska, Woodrow said. “There’s just not enough proof that engineered logjams will protect roadbanks in our climate,” he said, citing questions about effects of a local freeze-thaw cycle.

In adopting new technologies, the state must act conservatively in order to protect its investment in the road, Woodrow said. “We want to make sure we preserve this road for decades.”

Woodrow described the vegetated river protrusions as a hybrid between the logjams and “woody debris piles,” a type of streamside habitat improvement already planned for sections of the project. The number and location of the protrusions have not yet been determined, Woodrow said.

Biologist Kirkpatrick said he’s hoping the state will incorporate designs by Herrera Environmental, a Seattle-based engineering firm that pioneered the technology and has been working with Klukwan on this issue.

Kirkpatrick said vegetated river protrusions are a general concept, and that any new structures that push flow out into the river must include engineering for a rebound effect when the flows come toward the road downriver.

“It’s critical to design them right or the river will erode the bank downstream a little way. The concept is doable if it’s done right, with the right location and engineering, but until you have something to look at (on paper), it’s hard to say,” Kirkpatrick said.

Besides design and location, the number of protrusions will be important, Kirkpatrick said. He said engineered logjams protect roadbeds in Washington and Oregon. “They’re used quite extensively… This is about DOT and their comfort zone. It has nothing to do with the engineering.”

Woodrow said mitigation measures on the highway will more than match the project’s impacts on habitat.

“We’ve gone beyond one for one. We’re working toward the Boy Scout motto, to leave it better than we found it,” Woodrow said.

Kirkpatrick said the project’s environmental assessment hasn’t established that. “They didn’t put anything out there to show it’s one to one. That’s speculation, as far as I can tell from the EA.”

Woodrow said he didn’t have a response for an advisory committee concern that mitigation funds for the project be spent exclusively in the valley. Committee members are concerned that mitigation funds may go into a land trust that would benefit habitat elsewhere.