Sonoma Water asked to approve a $6.6 million upgrade to its Russian River diversion structure

By The Downspout · Posted Nov 4, 2026 · 3 min read

On November 3, 2026, Sonoma Water asked the Sonoma County Board of Supervisors to award a $6,602,150 contract to Corcus Construction, Inc. The job replaces pumps, electrical equipment and controls that have reached the end of their useful life at the River Diversion Structure on the Russian River. It was an item on the consent calendar, a list the board votes on together. The agenda page we read did not yet show the result. You do not need to do anything.

Where it is and what it does

The River Diversion Structure is a facility of Sonoma Water, the Sonoma County Water Agency. It stands at 10290 Westside Road, along the Russian River. It was built in 1975.

It takes water from the Russian River and sends it into a series of ponds. The water soaks into the ground and refills an underground layer of sand and gravel, called an alluvial aquifer. The county document says that aquifer feeds "collectors 3, 4, and 5." Collectors are a type of large well. Our page on where your tap water comes from describes them and the trip from river to tap.

The county document says the project helps Sonoma Water keep providing drinking water service.

See it on a map: River Diversion Structure, 10290 Westside Road

What happened

Sonoma Water staff asked the Board of Supervisors to do three things at its November 3, 2026 meeting:

Approve the plans and specifications for the project.
Award the construction contract to Corcus Construction, Inc. for $6,602,150.
Let Sonoma Water's general manager sign the standard form that closes out the contractor's claims when the work ends. If the contractor lists claims that are not settled, County Counsel, the county's lawyers, review the form first.

The item was on the consent calendar. That is a list of items the board votes on together. The agenda page we read did not yet show the vote result.

The old equipment has reached the end of its useful life. The county document says the parts are more than five decades old. The new equipment includes:

A medium-voltage switchgear and a step-down transformer. Switchgear controls and protects the incoming high-voltage power. The transformer lowers its voltage.
A motor control center, which starts, stops and protects the motors.
Vertical turbine pumps, which move the water.
A programmable logic controller, an industrial computer that runs the system.

The job also covers piping, lighting, heating and air conditioning, and access platforms. It adds a flow metering system with vaults and meters.

Sonoma Water advertised the job for bids on June 22, 2026. Seven companies bid, with bids received September 8. Corcus Construction's bid was the lowest that met the requirements. It is $30,250 below the engineer's cost estimate of $6,632,400.

What it means for you

You do not need to do anything. This is replacement of existing equipment at an existing facility.

The money is already in Sonoma Water's budget for the 2026-27 fiscal year, in a fund called Common Facilities. The county document says no extra money needs to be approved.

What happens next

If the board approved it, construction is scheduled to begin about December 14, 2026. The estimated finish is August 24, 2028.

Sonoma Water decided the project is exempt from the California Environmental Quality Act, the state law that requires environmental review of many projects. It cited two exemptions, one for existing facilities and one for replacement or reconstruction. The notice of exemption was filed in November 2025.

Where this came from

The Board of Supervisors' November 3, 2026 agenda, the county staff report on this item, and the state's CEQAnet record for the project. We did not read the attached bid summary. For how the river and its storage lakes feed the supply, see how the Russian River works.

Sources

Checked 2026-11-04. Rules and programs change. If something here is out of date, the source above wins. Spot an error? See our corrections policy.