When Sea-Tac’s third runway opened for business on November 20, 2008, part of the Port’s $4.2 billion capital improvement program, all eyes were on Alaska Airlines’ Flight 674 to Denver, the runway’s inaugural commercial flight.
But those who knew of the many projects leading up to this opening also were applauding the wetland mitigation and storm water management programs, which were key to the airport's multi-year expansion project and to the runway’s construction.
After all, salmon recently had been spotted  swimming in Miller Creek, a nearby waterway that was relocated to make room for the new runway. This was an important indicator of successful habitat construction.
"It was very rewarding to see salmon return to the creek, and is a testament to the work we did and the success of our mitigation," said Elizabeth Leavitt, director of Aviation Environmental Programs at Sea-Tac.
Part of the early primary design criteria indicated the creek had to be a suitable habitat for the fish. The work included removing septic and heating oil tanks that had been part of the since-removed homes, as well as trash and old tires that had accumulated in the previous creek.
In all, 1800 feet of the waterway was pushed to the north. The remaining 6,500 linear feet of creek was restored with 168,000 native plants and more than 200 pieces of large, woody debris. The latter worked to enhance the water’s surroundings, allowing a spawning habitat and a place for the fish to hide.
"It’s now a much more complex habitat that provides greater variety beneficial to trout and Coho," said Bob Duffner, water resources manager.
In addition to improved creek habitat, the Port restored and enhanced more than 70 acres of wetlands surrounding the airport. This work mitigated impacts from the runway embankment construction which resulted in the fill of nearly 14 acres of wetlands.
A challenge for the mitigation, Duffner recalled, was to enhance the adjacent wetlands but keep them from attracting large birds that could interfere with air safety. This was handled by planting mostly berry-less plants and low shrubs.
However, bird habitat is a vital function that wetlands generally provide. To address this need while ensuring air safety, the Port also constructed a 67-acre wetland complex in Auburn near the Green River that specifically incorporated water features and habitat functions preferred by birds. See the video.
The Port aggressively upgraded its stormwater facilities that drain to the creeks surrounding the airport. These efforts were recognized in the 2008 Environmental Achievement Award from Airports Council International.
"The ACI Environmental award is very important to airports in North America, and it was an honor to be recognized for our mitigation work, which is really cutting edge for airports worldwide," Leavitt said.
The route to that award dates back to 2002, when the airport was given a five-year window to design, construct and implement best management practices before receiving the permits necessary to construct the new runway.
The stormwater program involved retrofitting the airport and adjacent historic infrastructure, and delivering modern standards for flow control and water quality. Detention vaults and ponds store stormwater runoff and then release it slowly to prevent erosive flows. The table below shows the significant progress made toward meeting the airport’s goal of providing water quality treatment and flow control of runoff.
Other best management practices included wet pools and filters. "They’ve helped reduce levels of copper and zinc by 40 to 70 percent," said Bob Duffner, water resources manager. See the video.
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