Arcata Marsh & Wildlife Sanctuary

The Arcata Marsh is a 307-acre wildlife sanctuary on Humboldt Bay that is also, simultaneously, the last stage of the city's sewage treatment. Treated effluent from the wastewater plant flows through constructed marshes, where plants and natural processes finish the job before the water enters the bay. Arcata built it in the 1980s instead of a conventional plant, and it has been studied by engineers and visited by birders ever since.

The birding is the reason most people come. Over 330 species have been recorded here, on the Pacific Flyway, across freshwater and saltwater marsh, brackish ponds, tidal sloughs, mudflats and grassland in a space you can walk in an afternoon. Fall brings raptors and migrating warblers, winter brings waterfowl and roosting night-herons, spring the swallows and hummingbirds, summer the river otters and brown pelicans.

Five miles of surfaced, flat trails run through it, much of it genuinely accessible — the Humboldt Bay Trail North segment is paved Class I multi-use, and there's a balloon-tire beach wheelchair available to borrow at the Interpretive Center front desk.

Saturday is the day. The Redwood Region Audubon Society runs a free bird walk at 8:30am from the I Street elbow, and Friends of the Arcata Marsh lead a free 90-minute walk at 2pm from the Interpretive Center, rain or shine. There's also a cycling tour on the second Sunday of each month.

Everything is free. The sanctuary opens at 4am and closes an hour after sunset. Dogs are welcome on leash.

The Wiyot people stewarded this land as Soulatluk long before it was a landfill, a lumber mill, or a marsh.