PD Editorial: It’s time to weigh a water plan minus Potter Valley plant

It’s getting hard to find the lake at Lake Mendocino.

A bed of cracked, dry dirt grows steadily as the shoreline recedes, exposing abandoned homesteads that had been submerged for decades. State officials warn that the lake could go dry — a first for a major California reservoir.

Lake Mendocino is a crucial link in the North Coast’s water supply chain, and even a drought-busting winter won’t ensure its recovery.

The reservoir, which serves farms and towns from Ukiah to Healdsburg, usually receives about 30% of its water via the Potter Valley Project, a century-old hydroelectric plant that relies on water diverted through a mile-long tunnel from the Eel River and into the east fork of the Russian River.

PG&E owns the money-losing plant and plans to surrender its license when it expires in April.

A bid by North Coast water users to acquire the license hit what may be an insurmountable roadblock when federal regulators refused to extend the deadline for studies that would cost an estimated $18 million — if the money could be found.

That isn’t the only obstacle. A transformer failure has shut down the power plant and drastically curtailed water diversions from the Eel. Repairs would cost at least $5 million, maybe twice as much, and take as long as 24 months — if PG&E chooses to fix the transformer. Faced with millions in decommissioning costs, it wouldn’t be a surprise if PG&E doesn’t undertake any repairs.

It’s a grim picture for anyone who depends on Lake Mendocino for water, and it may be time to imagine a future without the Potter Valley power plant.

What is unimaginable is a future upper Russian River without water from the Eel.

The water users pursuing the Potter Valley license formed a group called the Two-Basin Partnership. Members include Sonoma Water, the Mendocino County Inland Water and Power Commission, Humboldt County, the Round Valley Indian tribes and California Trout. They have been working closely with Rep. Jared Huffman, D-San Rafael.

Their objectives include restoring flows on the Eel River, which once supported a flourishing salmon population, without the upper Russian going dry in the summer. To accomplish that, they want to limit diversions to wet winter months and store water in Lake Mendocino. To keep the Eel from running dry, they would remove Scott Dam, which creates Lake Pillsbury and provides a year-round water supply for the Potter Valley hydro plant.

Huffman raised some eyebrows with a suggestion that the recent setbacks may show “a faster and easier way” to the two-basin solution. But he may be on to something.

Operating the power plant would be a financial drain on the partnership, just as it has been for PG&E. Decommissioning would take less time than transferring the license, Huffman said, and PG&E is on the hook for those costs. The Two-Basin Partnership still could seek PG&E’s Eel River water rights and develop a plan to repurpose the diversion tunnel to direct winter flows for storage in Lake Mendocino, without the power plant.

“The key is keeping this two-basin coalition together,” Huffman said in an interview.

With a transfer of the Potter Valley power plant looking like the longest of long shots, this modified approach may be the last best hope for achieving two essential results for the North Coast: restoring the Eel River and preserving a vital water supply for Mendocino and Sonoma counties.

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