Officials move forward with plans for Eel River water diversions that keep Russian River flowing

Officials are moving forward with plans for a new pump system to secure continued diversions from the Eel River to supply Lake Mendocino and the Russian River.

The new system will replace structures that will be taken out when PG&E removes its two dams from the area.

The goal is to secure sufficient reservoir storage and year-round flows in the Russian River after Pacific Gas & Electric decommissions the Potter Valley hydroelectric project, which has channeled Eel River water for more than a century.

Officials also aim to improve conditions for fish migration past the site of Cape Horn Dam, once it’s demolished, facilitating their movement into the remote reaches of the Eel River. Passage to the headwaters currently is blocked by Scott Dam, which also will come down in the not-so-distant future, eliminating Lake Pillsbury.

On Tuesday, the recently created Eel-Russian Project Authority selected one of two alternative approaches to the new infrastructure. Members chose a pump station facility that would draw water from under the surface of the Eel River during still-undetermined, high, wintertime flows. From there, it would be pumped to a higher elevation and sent through an existing diversion tunnel into the East Fork Russian River.

Members of the authority include Sonoma County Supervisor David Rabbitt, chairman of the Sonoma County Water Agency and chair of the authority, as well; Sonoma County Supervisor James Gore; James Russ, tribal business administrator for the Round Valley Indian Tribes; Mendocino County Supervisor Glenn McGourty, representing the Mendocino County Water and Power Commission, and Janet Pauli, the commission’s chairwoman.

Assistant Sonoma Water General Manager Pam Jeane told authority members during the meeting that PG&E has assured agency officials it would coordinate on construction of needed infrastructure as the utility pursues demolition of Scott and Cape Horn dams, both parts of the Potter Valley power project being decommissioned.

PG&E is unwilling to include the new diversion facility in its own license surrender application for the powerhouse, so it will require a separate licensing process. However “they remain committed to working with the proponents,” and are supportive of efforts to permit, construct and operate a new facility, Jeane said.

The choice of a pump station was based on months of work by a Technical Advisory Group of biologists, engineers and water managers who rated two alternative approaches on a series of metrics like fish passage ease and safety, physical stability and resilience, construction costs and implementation.

Eel-RussianProjectAlternatives.pdf

The pump station came out on top in almost every area except operations and maintenance, given the mechanical complexity of the pumps.

The alternative, a roughened channel, would build up the river bottom using large rocks and precisely placed boulders to elevate the channel so gravity can be used to drain off a set amount for diversion. But it’s not been used before on as large a scale as is being contemplated for the Eel River and has some potential setbacks for fish populations.

Both alternatives had only been designed to a level of about 30%. The selection of a pump station means a $2 million grant from the Bureau of Reclamation will go toward 60% design of that alternative. It still would go undergo environmental review after that.

Planning for a new diversion structure is still in the very early stages. No parameters have been set for how high the Eel River flow must be, for instance, before it’s considered to have enough excess to be withdrawn and used elsewhere.

You can reach Staff Writer Mary Callahan (she/her) at 707-521-5249 or mary.callahan@pressdemocrat.com. On X (Twitter) @MaryCallahanB.