The Elk River Wastewater Treatment Plant in Eureka (8.6 mgd design) is a trickling filter-solids contact facility near the mouth of the Elk River, which separates the Northern California mainland from a large estuary that is part of the Humboldt Bay National Wildlife Refuge.

Directly in front of the plant is a 139-acre restored wetland that is also a part of the refuge. “Our operators are responsible for maintenance and keeping the pathway through the area open,” says Bruce Gehrke, utility operations manager. “The wildlife area was part of our mitigation agreement with the Coastal Commission that allowed the plant to be built.”

Diverse Funding

The pathway Gehrke refers to is a 1.5-mile multiuse trail that meanders through the wetland next to coastal willow patches, sand dunes and salt marshes. Known as the Hikshari Trail, it was recently upgraded through collaboration between the city and the Redwood Community Action Agency, a local nonprofit organization.
Funding for the $1.7 million project came through grants from the California River Parkways, a program of the state natural resources agency, the PG&E gas and electric utility, and the California Coastal Conservancy, a state agency committed to coastal preservation and access.
“Since the upgrade, the city Parks and Recreation department has become more involved, but we still do our part,” Gehrke says. The 10-foot-wide paved trail has 2-foot-wide crushed shale shoulders. Improvements include picnic tables, a truss span bridge, an observation tower, restrooms, an information kiosk and a parking area next to a boat launch.

Haven For Birds

“It’s really a pretty cool place,” says Gehrke. Humboldt Bay is a key stopover for millions of migratory sea birds. Thousands of geese, ducks, swans and shorebirds use the refuge each year.

Before the upgrade, the trail was a roughed-out area, essentially a sanctuary and a volunteer trail, says Miles Slattery, Eureka director of Parks and Recreation. “Now the path is a first-class trail that the operators pretty much take care of,” Slattery says.

The treatment facility is front and center to hikers, bicyclists, birders and other trail users. It is also on display through tours for community residents, including students. In addition to elementary and high schoolers, many students from nearby Humboldt State University and the College of the Redwoods regularly visit the plant and the wetlands.

Gehrke says the plant is unique because it uses the ocean’s ebb-tide to transport its treated effluent from a nearly 4-acre holding pond through Humboldt Bay to the Pacific Ocean: “Twice a day since the plant was commissioned in 1984, the tide has been the conveyor to our outfall.”

Beneficial Use

During periods of high rainfall, excess effluent is stored in two 2-acre facultative sludge lagoons. Biosolids are periodically dredged from the lagoons and applied at an agronomic rate on an 80-acre reclamation site owned by the city. The site is leased to a farmer who raises hay for baling and grazes cattle.

Says Gehrke, “We do everything we can to fulfill our stated mission to protect the public health and the environment and provide for the beneficial use of the waters and the natural wildlife habitat in the Eureka area.”