The planning stage of repairing damages to the seaplane base at the Renton Municipal Airport caused by flooding has now begun.

The Renton City Council approved two contracts with Mott McDonald to provide engineering services for dredging and the repair of the dock and ramp for seaplanes at the airport. The dock and ramp were damaged when the Cedar River flooded in Feb. 2020. The seaplane base at the north end of the airport also received a large amount of sediment deposits, logs and debris during the flood.

“Seaplane pilots and operators were having difficulty getting to and from the ramp we have on the lake,” Principal Engineer William Adams said.

Adams said the flooding was high enough to receive a presidential emergency declaration and authorized FEMA to assist with repairs. FEMA requested the city split up the damages into two sets for funding. The cost of the dock and ramp repair are not to exceed $293,600, and the cost of the dredging is not to exceed $481,900. FEMA is paying 90 percent of the costs for both design and construction, according to the agreement. The airport’s 10 percent share will be covered from the Airports Maintenance Dredging Project with an adjusted 2025 budget of $100,300.

The agreement by the city will bring the project to final design through the following scope of work: geotechnical survey, seaplane ramp condition assessment, preliminary engineering design up to 30 percent development of Joint Aquatic Resource Permit Application, final engineering analysis, bidding support and project management.

“These two contracts are to take it from 10 percent design all the way to bid,” Adams said.

Adams said they previously had a contract with Mott McDonald for almost five years where they performed initial sampling, sedimentation analysis and provided some alternative solutions, which the city presented to FEMA.

“We’ve been pursuing this final design effort, taking it to bid with 100 percent design, for a few years now. We’ve struggled with FEMA having some turnover at their project manager position. I think we’re on their third or fourth project manager, which has caused some delays,” Adams said.

Adams said they have been able to move some of the logs and debris out of the way for the seaplane pilots, but they don’t want it to accumulate anymore. Adams said the construction portion of the project is still several years away.

“Unfortunately the permitting to dig in a salmon-bearing lake or river takes quite a long time. It could take 12 to 18 months just for the proper people to approve our permit. For us to get to permit status is probably going to take us 12 to 18 months,” Adams said. “I’m hoping four to five years from now is when we are going to be digging in the lake and cleaning it up.”

Adams said this is not the first time the seaplane base has had this happen. He said a flood left sediment deposits in 2009, and in the pursuit of dredging it, it flooded again before they were able to get money for dredging. He said they finally dredged the area in 2013 with the same method they are currently pursuing.

“It’s kind of like a rinse and repeat, but we are trying to do a little more this time to try to prevent it from happening again,” Adams said.

Adams said they are hoping to control the path the sediment takes from the river.

“Our objective is to allow the sediment to deposit deeper into the lake instead of fanning out and depositing into our seaplane base. We’re trying to channelize the end of the river a little bit to allow the deposits to exit more north before they exit and block off our seaplane base,” Adams said. “That’s a dream. I don’t know where we’ll land with design and permits.”

Adams said there is a sight-seeing company that operates out of the base in the summer: “There’s virtually zero seaplane activity in the winter, just for safety. The lake gets too choppy and the winds are too high for them to fly on the lake. Once the weather turns for the better, their operations start changing and we see planes out every day in the summer.”