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Corps to remove 220 trees that pose risk to airport, 737 plant flood wall
The U.S. Army Corps of Engineers on Monday will begin removing 220 trees that pose a risk to a concrete flood wall along the Cedar River that protects the Renton Municipal Airport and Boeing's 737 production plant.
The work also will include removing all woody vegetation within 15 feet of the I-wall. The work will be visible from the Logan Avenue bridge over the Cedar River.
To help offset the loss of the trees and vegetation, the corps will plant willows at 12-inch spacing along 200 feet at the project site, as well on 1,620 feet of the river's bank across from the project.
The work is near Renton Memorial Stadium.
The corps will plant trees at Renton's Ron Regis Park along the river and some along the Elliott spawning channel as another mitigation site. That proposed off-site plan includes planting 408 trees, or three trees for each of the 136 trees being removed that are at least six inches in diameter.
Outside the 15-foot, vegetation-free zone, approximately 40 trees will remain to provide riparian habitat to aquatic life in the Cedar, according to the corps.
The $65,000 project, paid for with federal funds, will bring the flood wall into compliance with corps rules that require a 15-foot, vegetation-free zone. A corps analysis found that tree roots could damage the "structural integrity of the wall.
The corps expects to finish the work by the end of October.
The corps has coordinated the work with the City of Renton, U.S. Fish and Wildlife Service, National Marine Fisheries Service, the Washington State Department of Ecology, Washington Department of Fish and Wildlife and the Muckleshoot Indian Tribe.
The Cedar River flood wall, or I-wall, is designed to protect against a 100-year flood event level, or a flood with a 1-in-100 chance of occurring in any given year. Prior to its completion in 2000, damages started occurring on the left bank in a four-year flood event, or a 1-in-4 chance of occurrence; and at eight-year level on the right bank, or a 1-in-8 chance of occurrence.