River Mobile Estates residents know a thing or two about the shortcomings of the Reddington levee on the Green River north of Brannan Park in northeast Auburn.

And lest they forget, all that water that sometimes sloshes through the park on fall and winter days will be there to remind them.

King County officials say that the levee east of the mobile park, built more than 50 years ago for the sake of flood protection to surrounding agricultural lands and prone to seepage, is not up to today’s design and construction standards.

“The Reddington levee contains the 100-year-flood event in that channel as it is right now, but that’s about all it does,” said Steve Bleifuhs, manager of the River and Floodplain Management Section of King County. “In terms of its construction, we know it’s not adequate.”

Part of the problem is that the builders put the levee on the river side of a former channel, which is a wetland today. So while the levee keeps the flood within the channel, it also cuts off the wetland that stores the water, backing it up and flooding the adjacent mobile home park.

Devastating flooding impacts, Bleihfus said, are possible if a flood exceeds the channel capacity through that section of the river.

“We just don’t know what will happen with climate change and with the Howard Hanson Dam if it needs to release some more water, as well as other issues,” Bleihfus said.

But the old levee is about to go away.

King County expects to start later this year on the $12 million Reddington Levee Setback and Extension Project, which will increase channel capacity by moving the setback away from the river and building the levee west of the wetland. The flow containment capacity of the levee system will increase beyond its current 12,000 cubic feet per second.

Where the levee stops just north of the mobile home park, its replacement will extend to the north, making it more than a mile long. By doing that, county officials say, they will protect not only the mobile home park but also 596 impacted parcels, 321 residential properties, 275 commercial properties and 964 structures in Auburn and in the county.

The total value of the land plus buildings is about $680 million based on 2009 assessed values.

When the project is done, Bleihfus said, the protection level the levee affords should increase from its current 100-year to a 500-year flood event.

“We feel we’ve got so many people living in the valley and so much infrastructure and jobs that it really does necessitate a higher level of protection for those folks,” Bleihfus said. “So we’re going to build this thing a little bit taller, a little bit wider. In terms of the width, we want to make it wider to give it more stability. We also tend to dig farther and deeper down into the river channel today to create a toe or foundation to resist river scour. We just have more engineering knowledge and construction techniques today than we did in the 1950s and early 1960s.”

The top of the levee will be incorporated into the Green River Trail.

The project is expected to improve riparian processes and functions by setting back the levee to allow for more natural channel movement within the project area, allowing the river to meander, scour and develop a more complex ecosystem, including rearing habitat for juvenile salmon.

Construction is planned for 2013, but timing depends on King County’s ability to acquire the necessary properties. The King County Flood District has been awarded a DOE grant of more than $1 million to help fund the project. The grant funding is contingent on having most of the project finished by the close of 2013.

16 homes impacted

Property acquisition is the critical path item to meet this construction schedule, Bleifuhs said, involving 16 mobile homes on an essential stretch of land within the park.

“We need the property because it’s the only alignment that allows us to build the levee in a stable configuration in a way that actually provides bona fide flood protection to the property owners and the other lands behind the levee,” Bleifuhs said.

King County is moving through eminent domain or condemnation proceedings to acquire the properties. County officials have been communicating with the California-based owner of the mobile home park for about two years

Work with the homeowners has picked up steam during the last nine months.

“We are dealing with the property owners in accord with federal relocation act requirements, which give them significant monetary benefits and assistance to find new places to live,” Bleifuhs said. “We’re not saying we’re going to alleviate all their concerns about having to get up and move, but we are really working with them quite extensively to find new places. … It must be at a level compatible, even to a degree better, than their current living conditions. If they find a place that’s a little more expensive, we offset that. We will help pay for the moving costs. We buy their existing mobile unit for fair market value. So there’s a lot of advantages.”

Several locations are available within the mobile home park.

“We’ve looked around at some other mobile home parks in the area that have availability as well, and the property owners are talking and negotiating with the City of Auburn to buy some adjacent property directly to the south, where they could strip some additional pads and provide opportunities for those residents and others to move to,” Bleifuhs said.

There are worries within the community. “We have concerns,” said David Craven, property manager of River Mobile Estates. “The county wants to run a levee through my community instead of where they originally planned to do it. They want to remove 16 of the houses of low-income seniors.

“There’s no doubt that there’s an issue with the levee, but the county is trying to make it sound like they are doing us a favor by putting it where they are talking about putting it instead of elsewhere. The flooding issues are caused by a culvert the county won’t repair.”