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Getting ahead of high water: King County Flood district seeks short-term fixes, long-term solutions in the Valley
The 2,500-pound boulder nestles into place with hardly a splash.
Guided by the hand signals of a construction worker, Cory Marvin of Auburn, and moved by the enormous strength of a Caterpillar-tracked hydraulic arm parked on the bank above, the huge stone settles into a precise position, to be locked into place and, it’s hoped, stay put for generations.
Marvin and fellow employees with Gary Merlino Construction of Seattle have been visible along Snoqualmie’s Park Avenue Southeast riverbank for a week. They’re doing the hard work in a $150,000 riverbank repair project for the King County Flood District that’s scheduled to last through November 20.
With fall rains upon us, “Getting this done is important,” says Clint Loper, the flood district’s supervising engineer for the Snoqualmie River basin.
Many residents may not even be aware that a stone revetment protects Snoqualmie. But when the river gets low enough, the rocks become visible.
“The river is right up against the road,” Loper says, and the current makes a tight turn.
The so-called minor floods of last February and March scoured away part of the protective stonework, and while the road remains safe to drive on, erosion could threaten Park Street and a buried water main. About 130 feet of riverbank need attention, and that’s why Park Street has been closed to one lane this afternoon as the big earthmover drops stone into place.
Levee management projects like these are part of the mandate of the King County Flood District, which was was established in 2007 to oversee the region’s rivers and marine shoreline.
It is overseen by the members of the King County Council, but is an independent entity from the county—although there has been talk of merging the two together.
Once the work on Park Street is done, the county still needs to examine signs of instability in the river bank in the long term, to ensure Park Street stays put for good.
“This is an important short-term fix to make sure that damage to the revetment doesn’t get worse and more costly,” Loper said.
The Park Street fix, actually titled the Record Office Revetment project after the nearby Valley Record building, started two weeks ago. This project follows the typical pattern for flood fixes in King County. Flood district inspectors go out when the river is low and look for damage from floods and the current.
Their reports trigger work in the late summer and early fall, when construction companies armor the river’s edge and levees in stone.
This year, the county only scheduled a handful of repair projects. Big floods, like the January 7, 2009, deluge, which reached 60,000 cubic feet per second in Snoqualmie and 82,900 cfs in Carnation, can trigger dozens.
For the long-term approach, the county is considering major retrofits of its flood defenses.
“We’re putting together a game plan for larger projects,” Loper said—major construction work that makes for less damage and fewer costs over time.
One such example in the Lower Valley is recent Tolt River work that set the levee away from the river. That means the floodplain has room for river flows, while the levee structure is at less risk from the current.
Now being given a seven-year update in 2013, the county’s next Flood Hazard Management Plan includes needs in the Upper Valley. Loper identified possible big-picture flood fixes along the South Fork in unincorporated King County and the Middle Fork east of North Bend, along Mount Si in the Tanner area.
“We’re doing a lot of technical work, having discussions with cities, landowners, neighbors, and moving toward what the right set of projects are,” Loper said.
A public draft of the plan is in the works.
• You can learn more about the King County Flood Control District at www.kingcounty.gov/environment/waterandland/flooding/flood-control-zone-district.aspx
King County Flood Control District contractors with Gary Merlino Construction armor the bank of the Snoqualmie River along Park Street. The flood district seeks to employ short-term fixes like the Park Street work with long-term flood solutions, such as projects envisioned on the river’s Middle and South Forks near North Bend.