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Restoration - Lively Lagoon

This April a long-legged, chestnut-colored bird stopped off in a lagoon near Davis to rest. But this was no ordinary bird, nor ordinary lagoon. The bird, a white-faced ibis, is a state Species of Special Concern and the lagoon treats wastewater from the Davis Water Pollution Control Plant.

Each day, up to 7.5 million gallons of near tertiary-treated wastewater is pumped 1.5 miles from the city of Davis' plant to the new lagoon, which has been fully operational since this January. The water from the wastewater lagoon and stormwater from a second lagoon then flow by gravity into a pond where they mix together. The combined waters then flow on through seven more tracts or ponds, in which suspended solids and organics settle outor are absorbed by plants and microorganisms. The entire cycle takes around 90 days, according to Mike Conner, wildlife resource specialist with the Department of Public Works.

Once the water has circulated in the final pond, it is either discharged into the Yolo Bypass or recirculated for further oxygenation. The city hopes to eventually send the water on to farmers and ranchers in the area for re-use. In the meantime, Conner is keeping close tabs on the water quality gains of the project. The project's permit requires him to regularly monitor benthic and water column invertebrates and duck and shorebird eggs for selenium (a concern since elevated levels have been found in the area's groundwater), as well as test sediments for metals.

The $6.9 million for the project came out of two pockets. The city spent $2.2 million, most of it on acquiring the property, known as the Conaway Ranch. The Army Corps picked up the tab for the remaining 75% ($4.7 million), as part of its new mandate to provide more environmentally-sound flood control and as mitigation for wetlands lost during construction of the Yolo Bypass.

The project also reflects Davis' efforts to offset increasing impacts from urban growth by preserving more open space and natural floodplain, and by filtering more stormwater through wetlands, according to Dave Pelz, Director of Public Works. To this end, Davis has also required developers to create several smaller "stormwater" wetlands throughout the area, some water from which can also be conveyed to the city's own wetlands.

Davis is not the first city to treat wastewater with wetlands. Arcata began using wastewater ponds in the early 1970s, and several other sanitary districts around the state, including Las Gallinas in Marin, and Sacramento, use wastewater ponds (the latter is an experiment in removing heavy metals). But the Davis project is the largest constructed wetland with treatment capacity in the United States and unique in that it was designed specifically for wildlife.

The primary wildlife features are islands. Each pond contains four of these: two larger islands planted with native grasses to offer nesting habitat for waterfowl, and two smaller "loafing" islands free of vegetation, where shorebirds and waterfowl can see predators sneaking up. Shorebirds also use the loafing islands for nesting. Tract 3 was designed explicitly for shorebirds: water levels are drawn down - or water is piped around the tract - to allow the ponds to become mudflats during peak migrations. In addition, the northern border of the wetlands, planted with 8,000 native trees and shrubs, provides critical riparian woodland habitat, says Conner.

Conner is thrilled that the project has attracted such diverse wildlife. "We've already broken county records for several species of birds," he says. The white-faced ibis was only one of several unusual birds - including a ruddy turnstone (more of a coastal bird) and a semi-palmated sandpiper (ordinarily an East Coast migrant) - seen enjoying the ponds. Other "regulars" include white pelicans and a peregrine falcon, not to mention 85 other avian species (later this year, the wetland will open for birdwatching). With the birds safe on their predator-proof islands, the coyotes, foxes and skunks now being spotted in the area are welcome too. "It's very dynamic," says Conner. "We wanted to simulate a natural system as much as possible, and it seems to be doing just that."

Contacts: Mike Conner or Dave Pelz (530)757-5686

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