December 17, 2021 — The Potter Valley Project is in a phase of uncertainty, but a recent feasibility study could be a blueprint for a future that includes a diversion without dams.
The deadline for the license application is coming up in mid-April, and PG&E, which owns the project, has made it clear that it does not intend to renew. The coalition seeking to take over the license hasn’t come up with the money it needs to fund the necessary studies. And PG&E is not paying for a costly repair at the powerhouse that drastically reduces the amount of water the project is able to divert from the Eel River into the Russian River and on into Lake Mendocino.
The new study, a technical memorandum funded by the California Department of Fish and Wildlife with cannabis taxes, posits a few strategies for decommissioning the dams and building structures to continue seasonal diversions.
Darren Mireau, the North Coast Director of California Trout, signaled that he favors the rapid removal option with pumping. (CalTrout is a member of the Two-Basin Partnership, the coalition of entities that has filed a notice of intent to take over the license, but Mireau is not speaking on behalf of the entire Partnership here.)
He says sediment, both of the sandy and the rocky varieties, will play a large role in how any of the alternatives is carried out. Sediment buildup that reduced the capacity of the van Arsdale reservoir behind Cape Horn Dam was a large part of the reason Scott Dam and Lake Pillsbury were built in 1922, 14 years after Cape Horn.
“You’re goint to have an impact with sediment release, and you could do that once, or you could do that four times,” he said of the rapid removal option, as opposed to the phased approach, which would take place over four years. “And each time has about the same caliber of impact. So it seems reasonable to do it all at once and get past the impact, and get the dam out.”
Since the point of dam removal is to protect fish, Mireau added, “We would time it in a way that most of the fish are coming up the Eel River and heading into tributaries, so they’ll be distributed out of the effect zone…like I said, this is a feasibility level study right now, so a lot more detailed study will unfold.” Some options include a partial removal of Cape Horn Dam, but Mireau was unambivalent about CalTrout’s position on Scott Dam. “We will certainly want to remove — or have PG&E remove, to be honest, the entirety of Scott Dam,” he emphasized. “It needs to go. With regard to Cape Horn Dam, it’s a little trickier, because it’s the diversion point for water going into the Russian River, and we’re committed to maintain that reliable water supply…this study is actually groundbreaking for us, because we now have three reliable infrastructures that we think would safely and reliably provide that water supply to the Russian River.”
Of the three alternatives, the pumping option would be the cheapest to build, at an estimated cost of $20 million, as compared to $35-$48 million for channel-building options. But the annual projected operations and management costs for the pumping scenario range from $309,000-$359,000, including water delivery costs to Potter Valley of about $284,000 per year. Annual O&M costs for the other two options range from $50,000-$200,000. But Mireau doesn’t have a problem with water users paying the price for the commodity.
“Any water diversion at that location is going to have some annual operation and maintenance costs,” he said. “That’s unavoidable. The advantage of the full removal of Cape Horn Dam with that pumped diversion approach is that you get all of the obstruction out of the river that might impair fish passage.That alternative for Cape Horn Dam does that the best. And it does shift the cost, I think, to the water users, instead of the fish side, where it appropriately needs to be.”
Reached by phone, Congressman Jared Huffman acknowledged that PG&E ratepayers are likely to get stuck paying for any alternative that ends up being implemented at the project. But he said ratepayers are already paying for hydropower costs, and PG&E is currently operating the Potter Valley Project at a loss of about $9 million a year. What happens next depends on the federal regulators.
If surrender and decommissioning is the way forward, it will depend on an order from the Federal Energy and Regulatory Commission. The Two-Basin Partnership is likely to withdraw its notice of intent to apply for the license, according to Mireau. “We’re reasonably certain that will happen in ‘22, at least by the expiration date of the license itself, which is April 14, 2022,” he said. “And then FERC will turn and order PG&E into that surrender and decommission process…and then it’s PG&E, the license holder’s obligation to respond, start developing a plan for that decommissioning, and go forward from there.”
Huffman said that, although surrender and decommissioning scenarios do differ, a dam that blocks anadromous fish passage, as Scott Dam does, would have to meet a set of regulatory standards so significant that, “When you add it all up, you see where agencies have weighed in, (and) the only way to meet standards is to remove the dams.”
The last relicensing of the Potter Valley Project took 34 years. Mireau thinks time is of the essence for the fish, which are drawing nearer to extinction. Huffman hopes the condition of Lake Mendocino and the crippled transformer in the powerhouse “should create a great sense of urgency.” He also noted “a reticence to give up on the license application.” But if the partnership doesn’t withdraw its notice of intent to apply, FERC is likely to wait until it misses the application deadline in April, just as the dry season is getting underway, before making the pivotal order.
“One or the other will happen,” Mireau predicted.

You can find more documents about the Two-Basin Partnership at

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