��������

While the treatment plant on the Skagit is standing its ground, that approach won’t work everywhere.

One river to the south, Katrina Poppe and John Rybczyk sledge-hammered a white, meter-long tube of plastic into the mud.

Rybczyk sported mud boots and shorts; Poppe, hip waders. Both were surrounded by sedges, rushes and other marsh plants near the mouth of the Stillaguamish River, just south of Stanwood.

The Western Washington University ecologists have been studying a soggy 150-acre plot with low-tech and high-tech tools.

“We pound it into the sediment, and then you extract it so you can have up to a meter of sediment,” Poppe said of their brute-force method of extracting data from mud. “It shows you the different layers.”

Those layers of sediment tell the story of evolution from marsh to farm to marsh again.