Sonoma County has approved a $4 million contract for the second phase of what could become a sweeping, $50 million environmental restoration project along Dry Creek west of Healdsburg.
The construction, scheduled for this summer, will complete the first of six miles of planned work along the creek, which serves as the artery for drinking water stored in Lake Sonoma to the north. Using the creek as an aqueduct to meet the needs of 600,000 residential and business customers in Sonoma and Marin counties has damaged the spawning grounds for delicate populations of steelhead trout and coho salmon, federal officials have concluded.
"The creek right now is a vibrant ecosystem," said David Manning, environmental resources coordinator for the Sonoma County Water Agency, "but it needs to be changed, in some places subtly and in some places dramatically" to accommodate the needs of the fish that once spawned there in great numbers.
The Sonoma County Board of Supervisors, which also heads the separate Water Agency, approved the contract unanimously last week.
Federal officials have ordered the agency, and the U.S. Army Corps of Engineers, which operates Warm Springs Dam at Lake Sonoma, to restore fish habitat by 2020. Because many details of the project remain uncertain, the Water Agency says, it is hard to tell how much the full project might cost or how the burden might be distributed among ratepayers and the state and federal governments. Estimates of the total cost run as high as $50 million.
That price, however, is cheaper than the alternative, Manning said, which would be to build a new underground pipeline to divert the drinking water flow out of the stream, allowing the creek to return to a more leisurely natural flow rate that is better suited to fish spawning. Such a pipeline could cost up to $150 million.
"That is a place we really do not want to go," Supervisors Chairman David Rabbitt said.
Dry Creek empties into the Russian River just south of Healdsburg and just a few miles upstream of the Water Agency's massive intakes near Wohler, where the water is piped to cities and special districts.
The agency's plan is to complete up to three miles of the restoration by 2018, at a cost of up to $20 million, then see if the fish populations are rebounding. If the first half of the project appears to be succeeding, another three miles would be restored; if not, county officials would have to dust off existing pipeline plans, he said.
Unlike the situation downstream of many reservoirs, where the dams may artificially reduce flows in the river, the problem in Dry Creek is too much water, as the agency draws from the lake in high volumes. In its natural state, Manning said, Dry Creek would see up to 10 cubic feet per second of water flowing during the summer, but since the dam was built in 1983, the flow has been around 10 times that.
While that means plenty of water for vegetation, insects, animals and people, it spells trouble for threatened fish, particularly the coho salmon, which are relatively poor swimmers and need quiet places to rest.
The restoration work, therefore, requires building side channels and ponds, and placing logs and boulders in the main channel to simulate the way the creek bed would have looked before agriculture, gravel mining and the water system operations took their toll. The hope is to allow the agency to continue to draw water from the reservoir at a higher-than-natural flow while still giving fish places to rest and hide from the current.