Of Time and the Wetland

Abstract

At the oldest of Arcata’s treatment wetlands, it’s now possible to walk on water. Over three decades of filtering sewage, Arcata’s wetland cells have developed floating mats of dead cattail stems and leaves underlain by living roots, resilient enough to support a person’s weight. The short journey across Treatment Wetland 3 is a strange experience, like walking on a soggy trampoline. Water seeps through the cattail mat and into footprints. On a February day, a dense maze of brown cattail stems stretches twelve feet above the wetland’s surface, their shaggy brown seedheads waving in the breeze. A stroll across the treatment wetland is as close as a modern American can hope to get to the feel of the floating tule islands that William Finley camped on in the upper Klamath Basin in 1905, and that crowded California’s unspoiled marshes before the Gold Rush. The floating mats in Arcata were created by accident when the city’s treatment plant operators increased the depth of the treatment marshes, part of an effort to improve their declining performance. To their surprise, the dense growth of cattail rose off the bottom and continued to thrive, roots dangling in the water. The wetlands have aged. “Arcata’s is the grandmother municipal treatment wetland,” says David Austin, an environmental engineer with CH2M Hill who specializes in treatment wetlands design. Austin remembers studying the Arcata wetlands as a student at University of California at Davis in the 1990s. “It was a pioneering system. Now it’s an old design— one that wouldn’t be used today.” In 2016, three decades after Bob Gearheart’s unconventional marshes began cleaning Arcata’s sewage, the city’s wastewater plant faced a crisis. During the cold rains of winter, the system often failed to perform to the standards set in its discharge permit. Every part of the plant had aged to the point where its performance was in decline. At the headworks, the two giant Archimedes screws that push raw sewage uphill through a coarse screen had been running for decades; their metal housings were rusting away.