At it’s regularly scheduled meeting Tuesday night, the Mat-Su Borough Assembly approved a contract between the Borough and Jim Psenak Construction, to repair and construct approximately 150 feet of the dike along the Talkeetna River.
The Talkeetna dike and the Talkeetna revetment were built in the 1970s. The dike runs from the railroad bridge, across the Talkeetna River, and along the south side of the river for about 1200 ft. The revetment sits further inland of the dike. It goes near the edge of the Susitna River on the south end, as the river wraps around town.
When the structures were designed, the Susitna River had three main channels, and the point where the Talkeetna and Susitna Rivers came together, was away from town. But now, the Susitna River has consolidated into mostly one channel, and it is pushing against the Talkeetna River just north of Main Street.
During the 2012 flood, the lower part of the dike was damaged, and it was repaired in 2017 using FEMA funds. But FEMA only allowed the Borough to repair the structure to the previous specifications.
The contractor for that project was Jim Psenak, and he had this to say about the repairs:
“When we completed that job in 17, we told the Borough that they stopped short. This design was correct. It’s just that they didn’t go far enough, and we tried to actually talk to them in 17 and say, you need to go with bigger rock than what you got here. This is just not for the amount of water that’s flowing down these rivers. This rock is going to wash away. It can’t stay in one place with that much velocity.”
For the repairs scheduled in 2020, the Borough has the ability to use larger rock; Class Four rip rap with some boulders weighing up to 5,000 pounds. But the Department of Public Works acknowledges that, while the project will reinforce and improve the structure, the ultimate solution is longer term.
At the meeting, Doug Simon of HDL Engineering Consultants described the next steps:
“The long term solution does involve redesigning that system to account for the Susitna River. That will need a full survey of the river to make sure what the Susitna is doing now. That will need a full H&H Analysis to do that redesign and will look in form and function very similar to the 2017 repairs as far as it being a large plan set that’s designed, bid and built by a contractor. I can’t tell you for sure how long these repairs will last, because I can’t predict if we’re going to have another 100 year event or when that will happen. But it is designed to bridge us from where we are now until was can get a long term solution designed and implemented, pending what Mother Nature throws at us.”
