Green River levees slowly deteriorating

Andy Levesque stands atop a levee that keeps the Green River from flooding one of the most valuable commercial and warehouse hubs in King County.

At his feet are cracks that streak along the levee like lightning. They are worrisome because some are new and others widened after 27 straight days of rain in December and January.

The stress lines probably run through the levee to the very bed of the river, said Levesque, a county flood-control engineer. "It hasn't cut loose, but you can see that it's cracking and moving."

The damage to Kent's Briscoe Meander Levee appeared recently enough that it is not yet included on a growing list of needed flood-control projects on King County rivers. Even before these latest cracks appeared, the county found the Green River's deteriorating levees need $10 million in repairs to prevent "a potential regional flooding catastrophe."

Countywide, a draft Flood Hazard Management Plan says there isn't enough money to rebuild all of the levees, widen river channels and move homeowners to higher ground. The 10-year funding shortfall, according to the county, is $112 million.

At greatest risk along the Green River are Southcenter, downtown and industrial parts of Kent, and low-lying parts of Renton. Billions of dollars' worth of shopping centers, housing developments, warehouses and factories are in areas that could be flooded, according to the report.

The Southcenter retail and Andover commercial districts of Tukwila narrowly escaped flooding in 1990 and 1996. Both times, water seeped under the levee at Segale Business Park, saturating the soil and sending up small geysers.

Elsewhere in King County, levees on the South Fork of the Snoqualmie River in North Bend also have "extensive geotechnical deficiencies."

In Pierce County, the National Flood Insurance Program believes, low-lying areas of Fife and the Port of Tacoma could be flooded by the Puyallup River, whose levees aren't high enough and aren't maintained east of Interstate 5.

King County engineers aren't predicting any New Orleans-like collapses of the levees, but they say risks are is growing.

"Future floods will over time exceed the capacity and protective abilities of these flood-protection facilities, threatening property, lives, major transportation corridors, communities, and regional economic centers," according to the draft flood plan.

Hurricane Katrina, which overwhelmed New Orleans' levees last year, has given county officials a new sense of urgency.

Katrina was a reminder that a levee system is only as effective as its weakest link, said Steve Bleifuhs, King County's river and floodplain manager.

"If you look at the success rate [of New Orleans' levees], they were about 99.9 percent successful, but it only takes one break to do damage in the billions and billions of dollars," Bleifuhs said.

How the river was tamed

The first levees in the Green River Valley were built by farmers in the 1870s and 1880s, who used whatever materials they had on hand, Levesque said. Farmland began to be replaced with aircraft factories and other urban development after construction of the Howard Hanson Dam helped tame the Green in the 1960s, aided by a continuous system of levees.

But by 1990, flood-control officials began to realize that many of the levees were poorly built and were deteriorating.

When water seeped under the Segale Levee, emergency crews worked through the night to dig trenches and bring in truckloads of rocks and gravel. They averted disaster, but even after spending $2.8 million in repairs, they didn't complete all the work that is needed.

The worst problems found on the Green River are around the Segale, Desimone and Briscoe levees near the Kent-Tukwila border, and along Kent's Riverbend Golf Complex.

Consultants have been hired to study the Briscoe Meander levee's condition. The inner walls of the levee, like most, are too steep, allowing river-borne sediment to "slump" and take parts of the levee with it. The new plan proposes to widen selected levees and reshape their inner walls — a tough job since some warehouses are built almost to the edge of the levees.

At Kent's Narita Levee at Riverbend, 1,000 feet of a paved trail at the top of the levee has settled and cracked. The county found the levee's steep inner slope is "grossly unstable." A failure of the same levee section in 1965 flooded much of the valley.

Ryan Larson, Tukwila's surface-water engineer, said he supports the county's plans for rebuilding the levees so they aren't so steep, but he wants to make sure citizens aren't unnecessarily alarmed.

"We shouldn't be leaning on the panic button," Larson said. "I think we have time to plan it and find the funding and plan a program to do it. In the meantime, should people at Southcenter be worried that when the river is high it's going to flood? I don't think so."

The deterioration of the Green River levees stands in contrast to King County's otherwise exemplary record on flood control.

The federal government's National Flood Insurance Program has ranked King County second (behind Tulsa, Okla.) out of 1,028 jurisdictions for its work in assessing and reducing flood risks.

The county flood plan lays out several options for raising $112 million in new flood-protection funds: increasing the River Improvement Fund levy, creating new countywide or basin-level flood-control districts or raising surface-water management fees.

A countywide property-tax levy would cost $14.32 a year on a $400,000 home.

John King, a private-sector flood specialist and vice chairman of the citizens' advisory committee on the flood plan, said committee members are leaning in favor of sharing the cost countywide.

"If the Green River blows out and floods Tukwila, it's going to affect us all. If a Boeing factory is flooded, it impacts all of the county," King said.

County Executive Ron Sims is expected to send a levee funding recommendation to the County Council in May.

Keith Ervin: 206-464-2105 or kervin@seattletimes.com