Interim Report Validates Third Runway Environmental Initiatives

Miller Creek Wetland May Benefit From Removal of Homes

(Seattle)-- An interim report by the Washington Department of Ecology indicates that the Miller Creek basin has been affected by years of residential use, and for some environmental elements, would benefit from mitigation work planned in connection with construction of a third runway at Seattle-Tacoma International Airport.

"We're pleased that, at this stage of their study, Ecology staff and consultants agree with our approach," said Third Runway Project Manager Michael Cheyne. "By removing nearly 300 failing septic tanks, along with non-native plant species, the Miller Creek wetland can be improved."

The Port plans to mitigate about 18 acres of wetland west of the new runway, at a three-to-one ratio. Nineteen acres of wetland will be preserved in the local basin, with the goal of managing storm water and stream flows. Another 36 acres of wetland would be created near Auburn, specifically designed for the needs of migrating waterfowl. FAA regulations prohibit the creation of bird-attracting wetlands within 10,000 feet of an airport.

Ecology's interim report, released Monday, supports other aspects of the third runway environmental plan.

Port procedures for determining soil types and depth-to-groundwater were "consistent with accepted professional practice."
Most fish found in Miller, Des Moines and Walker creeks were Coho salmon, not listed as endangered under federal law. Ecology consultants found no Chinook salmon (an ESA listed species) in the creeks.
Fill material from a Maury Island gravel pit can potentially be used, if the top 18 inches are discarded. The pit was downwind of a now-defunct copper smelter, and the top 18 inches are contaminated with heavy metals.

"No source of fill material for the runway embankment has been determined," said Cheyne. "But there has been a great deal of speculation about the Maury Island material. We appreciate Ecology clarifying the topsoil issue."

The Ecology report also revealed something the Port has known for a long time: environmental records for the area are not up to date. The consultants found many wells in the area were not reported as abandoned when previous landowners switched over to a public water system.

"These wells have been open and unused for years, providing a potential route for pollutants into groundwater," said Cheyne. "The Port will take responsibility for properly decommissioning these wells as part of the third runway project."

The only area of difference between the Port and Ecology's consultants involves stream flow modeling west of the airport. Cheyne described the differences as "minor," and said the Port would sit down with Ecology to explain how its numbers were developed.

"One way or another, we will provide enough stormwater detention to keep this project from creating flooding and erosion problem downstream," said Cheyne.

The Ecology report is a "Mid-Study Fact Sheet." A final report will be presented to the Washington State Legislature by June 30, 2000.