Thousands of trees might have to be removed along the Green River levees from Kent to Tukwila because of a U.S. Army Corps of Engineers draft policy that states the roots of trees can damage the levees and need to be taken out, a Kent city official said.
“Over 500 trees were taken out last year and we’re looking at thousands that would have to come out from Highway 18 to the Duwamish,” said Mike Mactutis, a city environmental engineering manager, at a City Council workshop Tuesday about the levees.
The Green River becomes the Duwamish River near north Tukwila before the river flows into Elliott Bay in Seattle.
Kent city officials need to know whether they must remove the trees, as part of repairs planned this summer on the Horseshoe Bend levee, south of downtown.
“We’re working on the issue of trees-versus-levees the best we can,” said Tim LaPorte, city public works director, to the Council.
The Council will make the final decision about what steps the city should take to repair the levee.
As it stands now, if the trees aren’t removed, the city potentially could lose out on federal funds to help pay for expensive repairs to the levees.
“The county and city could choose to leave the trees in, but then we would be ineligible for federal repair funds if the trees damage the levee,” Mactutis said. “We got nearly $18 million in federal funds for the Riverbend and Horseshoe Bend projects.”
City, King County, state and federal officials have made repairs of the Green River levees a high priority to protect property from flooding, due to Howard Hanson Dam no longer operating at full capacity to protect the cities of Kent, Auburn, Tukwila and Renton.
The corps has estimated that a permanent fix (most likely a concrete wall) to a damaged abutment next to the dam could take three to five years to complete. A heavy rainstorm in January 2009 damaged the abutment.
The corps planted nearly 10,000 trees and bushes last fall along three rebuilt levees in Kent and one in Tukwila at a cost of about $500,000. Many of the trees were planted along the levee next to the Riverbend Golf Course in Kent.
The vegetation along the banks helps provide shade and cover for fish and offsets some of the impact on fish that work crews performed in order to widen and strengthen the levees, said Doug Weber, a levee safety program manager for the corps in Seattle, in an interview last October.
But the draft policy under consideration for adoption by the national headquarters of the corps in Washington, D.C., could lead to the removal of those trees just planted last year.
“It really depends,” Weber said in a phone interview Wednesday. “Under our Seattle district variance (from the national policy) they can stay. I hope they can stay because we invested a lot of money on those trees. But even if there is a change, they could stay if King County asks for a variance.”
Weber said Kent and county officials also could request a variance from the corps national headquarters for the project at Horseshoe Bend. Crews finished part of the Horseshoe Bend levee repairs last year, but more work needs to be done.
“There are trees that need to be monitored and when they become a certain size or condition they need to be removed,” Weber said.
Weber said the national policy to remove all trees along levees has yet to receive final approval. He did not know a timeline for when that policy might be considered for adoption.
Weber said the estimate that thousands of trees might have to be removed between Kent and Tukwila seemed accurate, if the national policy applies as well to the Seattle district.
“We’re in a period of unknown,” Weber said. “We’re waiting for the final policy so we know what direction to go.”
LaPorte said tree removal plays a big role in what direction the city takes for repairs to the Horseshoe Bend levee.
“The levee now is on top of the (Green River) trail,” LaPorte said. “We would have to move that if we need to remove trees and where the detention pond is now we would have to drop it down deeper.”
LaPorte said the debate about whether trees are good or bad for levees has caused disagreement between the corps and the National Marine Fisheries Service, a federal agency that wants tree along levees to protect fish habitat.
“They do not see eye to eye,” LaPorte said.
Levee systems in other parts of the country, including Sacramento, Calif., and New Orleans, where Hurricane Katrina struck, also are part of the debate about whether trees are good for levees.
“This is a national-policy debate,” said Ben Wolters, city economic and community development director, at the Council workshop. “We’re a flashpoint because we have all of the issues in one area. What Tim (LaPorte) described is a Rubik’s Cube that we have to solve to address the levee issue and get the Kent industrial area out of the floodplain.”
The completion of the Horseshoe Bend levee would help protect much of the Kent Valley industrial area. Kent has received $10 million from the state Department of Ecology for those repairs in an effort to get the levee certified by the Federal Emergency Management Agency. If certified by FEMA, much of the Kent industrial area would no longer be in a floodplain and property owners would not have to buy expensive flood insurance.
The corps has plans to rebuild the Upper Russell Road levee, north of Riverbend Golf Course, in 2011, LaPorte said. The number of trees to be removed along that section remains to be determined.
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