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Pacific Gas and Electric’s (PG&E) Potter Valley Project has failed at the primary purpose for which Cape Horn and Scott dams and the diversion to the East Branch Russian River were built. After the transformer at the Potter Valley powerhouse failed in 2021, PG&E declined to buy a new one. The dams will never produce another watt of power.
Fortunately, this benefits PG&E’s embattled ratepayers. Between 2005–2016, the Potter Valley Project (PVP) generated less than ¼ of a percent of all PG&E’s hydroelectric production, yet the PVP cost PG&E (or rather, its ratepayers) more than twenty dollars for every dollar’s worth of electricity it made. PG&E cites the significant economic losses of the project as a primary factor in their 2019 decision to withdraw their relicensing application.
But while the economic losses started PG&E on the path toward decommissioning, it’s clear that dam safety issues at this century-old, high-hazard facility are what is really motivating PG&E to act quickly to remove this massive liability.
Seismic risk is amplified by structural issues
Scott Dam, which impounds the Lake Pillsbury Reservoir, sits nearly atop the Bartlett Springs Fault Zone, capable of generating a magnitude 7 earthquake. Many elements of Scott Dam’s design and current condition compound its seismic risks.
U.S. Congressman Jared Huffman recently shared at a public meeting that an engineer with PG&E told him that of all the utility’s projects “Scott Dam is the one that keeps me up at night.” Scott Dam was originally designed to go straight across the river. During construction, however, builders discovered that what they thought was bedrock on the southern abutment was actually a giant boulder that shifted during construction. This required a seat-of-the-pants redesign to build the rest of the dam in front of the boulder (it’s the dark purple blob in the image below), at a sharp angle to the rest of the dam.
Meanwhile, the Eel River, according to the United States Geological Survey, “has the highest recorded average annual suspended-sediment yield per square mile of drainage area of any river of its size or larger in the United States.” This sediment has been piling up in the Lake Pillsbury Reservoir for over a century and is now placing significant pressure on the upstream face of Scott Dam.
These walls of sediment will at some point collapse and block the only low-level water outlet. When that water outlet, controlled by a needle valve, stops working, PG&E will only be able to release water when Scott Dam is full. Since this problem was identified, PG&E has managed the reservoir to maintain at least 12,000-acre feet of water.
Like any century-old infrastructure, the PVP dams are degrading and vulnerable to catastrophic failure. The Federal Energy Regulatory Commission (FERC) refused to address questions about the seismic safety of Scott Dam in the relicensing process, insisting that its dam safety division’s inspection process keeps all federally licensed dams safe. Nearly everything about dam safety in the PVP FERC docket is classified as Critical Energy Infrastructure Information (CEII), a designation that keeps all such information out of public view.
As Scott Dam was being built, serious questions were raised about the dam’s foundation, but no investigation was ever undertaken. Again, much of the information about the stability of Scott Dam’s foundation is concealed behind CEII classification.
Many dams built before we understood plate tectonics sit on fault lines. This is exactly the case for Scott Dam. The Bartlett Springs Fault is a part of the San Andreas complex, capable of generating up to a magnitude 7 earthquake.
In addition to Scott Dam’s precarious location, there is also an active landslide above the southern abutment of the dam. When Miller Pacific conducted a slope stability analysis in 2018, they concluded that the landslide, with a mass of over 8 million cubic feet, weighing over 520,000 tons, presents a significant geologic hazard. In PG&E’s 2016 safety review they state that the “susceptibility of these slopes to seismic events is not known and has not been studied.”
Failure as water supply infrastructure
When PG&E received an assessment of the seismic risk to Scott Dam in 2023, it quickly lowered the radial gates atop the dam, reducing the capacity of Lake Pillsbury Reservoir by about 20,000-acre feet. Combine that with the sediment accumulation that has both reduced storage capacity and requires PG&E to maintain at least 12,000-acre feet to prevent blockage of the only water outlet, and that leaves relatively little water to spare for diversions. What had previously been a significant asset for water users is now at best uncertain and very much at risk of complete failure.
When PG&E attempted to auction the PVP, they received no qualified bids. Representatives of water users in Sonoma and Mendocino counties are clear that this is due to the liability of the dams and the annual operating losses. They say, “we cannot operationally or fiscally take ownership of or fix both dams.” For more information about safety issues see bit.ly/dam/safety-series.
Thanks to the cooperation of stakeholders in both river basins, transforming the Eel into California’s longest free-flowing river will not end diversions into the Russian but rather allow for a change that will be more ecologically appropriate for both watersheds. Dam removal is the inevitable solution to the public safety and environmental hazard that the current project presents. And let’s not forget, dam removal is also the single most important action we can take to support recovery of the Eel’s native salmon and steelhead.
Alicia Hamann is the executive director of the Friends of the Eel River.
Interesting that you present the situation the way you and that idiot Huffman want it to look instead of the real facts. The dam is safe and has been rated so by the people that actually do the official ratings. There are over 100 dams in CA with the same or worse ratings than Scott Dam and none of them are coming down. How about PG&E is sick of people like FOER and CalTrout and everyone else pretending to have rights to the water with false facts, suing them and telling them how to run the Scott Dam. Someone is PG&E said we don’t need this headache any more, the project costs us money, and we’re tired of fighting them, let’s just get out from under it. Now they found out they are talking $ 500M – $2B and maybe no so happy and now they have to pass that cost on to their customers.
Also, guess what Alicia, the people of Lake County, Cloverdale, Potter Valley and many other actual stakeholders are getting fed up with Huffman and you all and are taking the fight to the highest levels of the US government. Possible filing an injunction and working to make sure the water stored in Lake Pillsbury is NOT destroyed by PG&E or any other entity and that the water is safe for fire protection, recreation, local habitat and actually protecting the river for all 12 months of each and every year. The lake provides control over the water flow that would disappear if that dam came down.
Maybe the Army Corp will take it over like they do Mendocino and Sonoma! In conclusion, it is not a done deal that the Dam is going to actually be decommissioned. While that is what PG&E has decided was their only option, that might just not be the case and the people like Lake County will actually get a say in what happens in their county for a change! Cuz it was 100% clear that Huffman was not going to listen to them. And people of Lake county and beyond will not have to pay PG&E’s higher rates if the project is stopped.
The same scare tactic used by the friends of the eel for the past decade plus. Selective reasoning, ignorance, or lack of recognition of a myriad of benefits, and providing only one “solution.“ Wake up and recognize the regional benefits to all. Never a mention that Ruth Lake has no fish ladder and its potential impact. Never mention of all the other contributing factors to the decline of fisheries within the ill river system. Looking for scapegoat.
Within a day of the Lake County Chamber of Commerce’s Lake Pillsbury Town Hall, Cal Trout and Friends of the Eel River have come out swinging. They want you to believe that dismantling the Potter Valley Project (PVP) is in the best interests of the public, but it is not. The PVP’s water transfer from the Eel River to the Russian River represents less than 2% of the total Eel River flows and it benefits 650,000 downstream water dependents in Mendocino, Sonoma and Marin Counties.
No one knows the true extent of the seismic issues of Scott Dam because that information is not public. Do not be misled. The study cited by the FOER was done by a consultant they hired. If Scott Dam was unsafe, it would have been drained by now.
Many people in Lake, Sonoma, Mendocino and Marin County do not support the dismantling the Potter Valley Project. We would like to see a retrofit of Scott Dam for seismic safety, fish passage, and fish restoration and habitat restoration downstream.
Two of the three lakes in our regional water supply system are owned and operated by the US Army Corps of Engineers (USACE). It makes sense that Lake Pillsbury, the third lake in our regional water supply system, also be operated by USACE.
Lake Pillsbury is the hub of the Mendocino National Forest. Lake County and Lake Pillsbury communities rely upon Lake Pillsbury for fire protection.
Watch the Lake County Chamber of Commerce’s Lake Pillsbury Town Hall to hear the other side of the story. https://www.youtube.com/watch?app=desktop&v=JjTRmX2UchQ
Why in the world would we ever get rid of water storage. The eel dries up east of the lake every year. I’ve deer hunted up there for 20+ years. Not to mention how invested the lake is with pikeminnows. What will they do to everything down stream???
You really need to start checking your facts better. There’s a lot of mistakes that you made in this article.
We need the water, that is distributed to 600000 plus people. We need the power that could be gained by upgrading power unit. We need the water for fire protection. We need the water for recreational purposes.
There is a fish ladder and a hatchery at Vanarsdale dam. They have been counting fish there for years. They are just not there. No coho samon for over 40 years , by fish and games own count. The dams actually help the fish population by providing consistent water during the dry periods.
You choose and Indian tribe that is not affected by that water. A trout group that has supported Congressman Huffman, and brought several law suits against PG&E to support your removal of the dams , while excluding the very county that the dams,water, and lake reside in from being on the the committee to investigate alternatives. That sounds a little suspicious to me.
Friends of the Eel, “More money please. We need to keep pretending that fake fish flows are more critical than people’s lives and properties. Give us more money – our lies and scare tactics are expensive, since they have to come from unsuccessful lawyers”.
Yes, FOER needs more money to pay themselves (the legal firm from out of the area). This has been a cash cow for them. Wake up people!
What have they done directly to protect and improve the Eel River?
Have they directed any River Cleanup projects like the Russian River Keeper has been doing along the Russian River? Any habitat restoration projects? Any patrolling of the Eel River looking for illegal water extraction and reporting the polluters? Any funding to eradicate the pike minnow or enhance the salmonoid populations? NON OF THE ABOVE THAT I KNOW ABOUT!
Instead of wasting all our money to fill legal firms pockets, we should all be working together to fix the POV, not destroy it, to provide water for humans and fish.
The Eel River needs our support in many ways. Let’s fix it!
Sonoma County DWR states in their 500+ page report that this plan is not the best option but it was the only one the NGO’s would agree to.
In addition to the 650,00 people in 4 counties…why has all of the wildlife not been mentioned? Over 400 elk, the deer, wild boars, eagles and so much more. Where will they get water to survive? Where is Peta, the environmentalist? Not a peep. The raking of the forest for fire prevention on snow mountain was prohibited do to some frog or some other animal (I don’t remember what the animal was). This is so stupid.
If the dam was destroyed by a natural disaster, where would the water and silt go? It is not near any populated area. It may destroy the logging road but it will go thru a channeled area for miles and miles. Why are they willing to spend millions on destroying it instead of retrofitting it?