As dams age and no longer become useful for their intended purpose, their threats to human health and safety and ecosystems often outweigh their value. 

Dams not only block fish access to critical habitat, they alter the river’s natural flow,  prevent rivers from transporting sediment and nutrients and also slow and warm water which encourages the growth of toxic algae and the proliferation of non-native species. These significant changes transform the ecology of rivers, often negatively impacting fish, wildlife, and people that rely on the services rivers provide.

Dam removal will restore the ecological function of the Eel River and allow it to work naturally, creating floodplains, wetlands, side channels, and marshes. These varied habitats all help improve water quality and support healthier native plants and wildlife. In short, free flowing rivers support healthy ecosystems and the economies that rely on them.

The Potter Valley Project is not viable as a business venture for energy production. Prior to deciding to decommission the Project, PG&E tried to sell the Project but no willing buyers stepped forward. PG&E has since said the project is unprofitable, losing $5-10 million per year in operations and maintenance costs. With no party willing to pay for the needed upgrades and continued operation of the project, PG&E will develop a plan to decommission the Project.

The owner of the Potter Valley Project, PG&E, is responsible for the facilities until FERC signs off that decommissioning of the Project is complete. This includes all costs associated with decommissioning the Project including studies, facilities removal, potential mitigation measures and any restoration activities that are included in the decommissioning plan.

Scott Dam has blocked fish passage to 288 stream miles of steelhead habitat and 89 stream miles of Chinook salmon habitat in the upper basin (Cooper et al 2020 (pdf). In addition to preventing fish from migrating to spawning grounds, the dams impede downstream movement of sediment, gravel and large wood, key drivers of healthy salmon habitat. Dams interrupt important ecological processes like nutrient cycling that can change food webs, ultimately impacting habitat suitability for miles downstream.

The smaller Cape Horn Dam has a fish ladder and counting station, but it is well understood that the facility needs significant upgrades to reliably and safely allow fish to pass. The fish ladder is closed during high flows to prevent sediment from filling it, often closing for a week or more in the middle of the annual steelhead run. Predation by otters is also a problem at the fish ladder because it creates an unnatural pinch point for migrating fish.

The dams slow and warm water creating habitat that is preferred by non-native pikeminnow and largemouth and smallmouth bass, predators that feed on juvenile salmon and steelhead. These source populations further contribute to population declines in native fish throughout the Eel River. 

The dams also prevent the passage of culturally important Pacific lamprey that migrate from the ocean to reproduce like salmon. Scott Dam is a complete barrier to lamprey. In recent years, enterprising biologists at Cape Horn dam invented a temporary tube system to allow lamprey to pass over the dam.

Threatened and endangered native salmon and steelhead populations would benefit significantly if they could access this habitat. A recent study by the National Marine Fisheries Service noted “…that the dammed subbasin has substantial salmonid capacity relative to the rest of the watershed and could provide an important cool-water refuge during warm years and from pikeminnow, potentially improving the productivity and resilience of multiple anadromous salmonid populations”. (Fitzgerald et al 2022 (pdf))

Headwater habitats such as those found above the dams are disproportionately important for baby salmon and steelhead compared to other reaches of the Eel River. Additionally, much of the watershed above the dams is public land and protected from future development as part of Mendocino National Forest and the Berryessa Snow Mountain Wilderness.

Dam operations will never be able to replace the habitat lost by blocking fish from the headwaters. The water released by Scott Dam is often too warm in the summer to support young salmon and the 12 miles of marginal habitat between the dams is a predator hot spot for non-native species that prey on juvenile salmon.

A number of dam safety concerns have been raised, including the fact that Scott dam is built directly on top of the Bartlett Springs Fault complex and the potential for low reservoir levels and accumulating sediment to clog the dam’s only outlet valve. Since dam safety information is protected as confidential, safety concerns related to the Project are often downplayed, but remain serious. Removing the dams would solve safety and liability concerns associated with the 100 year old Project.

Revegetated areas will provide wildlife habitat, and the restoration of salmon runs will provide food and nutrients to the upper Eel River ecosystem that it has been deprived of for a century. When adult salmon die after spawning, their bodies transfer marine-derived nutrients including carbon, nitrogen and phosphorus to the surrounding ecosystem. Decomposing salmon carcasses provide a food source for fish, wildlife and birds like bald eagles and osprey. Salmon are a keystone species and are known to benefit more than 100 other species. 

Tule Elk were introduced into the Gravelly Valley area in the 1970s and have become popular with hunters and for wildlife viewing. To date, no studies have looked at how dam removal would impact Elk herds and negative impacts should not be assumed. More study will be needed to both better understand these animals and how changes to the Project may affect them. 

Removal of Scott dam will likely benefit Foothill Yellow Legged Frog (a species of special concern) populations as Lake Pillsbury fragments a historically continuous population and promotes proliferation of non-native aquatic predators. Dam removal would allow fragmented frog populations to reconnect, promoting genetic diversity and population resilience.

Each of these issues (and more) are partially to blame for the decline of salmon and are the focus of ongoing restoration efforts. Nevertheless, studies show definitively that no single action would benefit Eel River salmon and the health of the river as much as dam removal. Scientists from the National Marine Fisheries Service recently described the basin above the dams as having “substantial salmonid capacity relative to the rest of the watershed” that “could provide an important cool-water refuge during warm years and from pikeminnow” making it a critical area to reconnect.

While dam removal will reduce reservoir- based recreation at Lake Pillsbury, it will support additional river-based recreation by improving river health and fisheries, which will attract a different type of recreational tourism to the region. An economic analysis has shown that the benefits of dam removal to local communities will result in $250 million in economic activity over the five-county region of study (Humboldt, Lake, Marin, Mendocino, and Sonoma), approximately $100 million of which is projected to be related to increased business activity and wages. 

How to manage the sediment behind both Eel River dams, but especially Scott dam, has been a major focus of studies over the last five years. Dams trap sediment instead of allowing it to move naturally downstream and nearly all dams eventually fill with sediment and cease to function, so the sediment will have to be dealt with at some point, either now or once more sediment accumulates making it even more difficult to manage and with greater environmental impacts. 

In the Scott Dam and Cape Horn Dam Removal study prepared by McMillen Jacobs Associates, scientists and engineers assessed multiple options for rapid and phased dam removals with and without sediment management, backed by additional studies on fine and coarse sediment transport and a hydraulic model. While additional study is needed, the reports suggest that both the phased and rapid removal approaches are technically feasible and have been successfully adopted and implemented on other projects of similar scale. 

Both dam removal alternatives are estimated to result in the release of substantial volumes of fine sediment, however, the rapid removal approach would have a relatively low likelihood of direct impacts on most species and life stages of fish and would be matched with the time of year when elevated suspended sediment occurs under natural conditions. In contrast, the phased removal approach would have additional impacts from multiple consecutive years of elevated suspended sediment releases, and the potential for fine sediment release during the summer when impacts to fish would be the greatest. 

In short, dam removal may result in acute but brief impacts to fish and the aquatic ecosystem, but impacts can be minimized with proper timing. In other dam removals, it has been demonstrated that these short-term impacts are greatly outweighed by the quick recovery of the system and the long-term benefits that result.

Fortunately, a study conducted on behalf of the Coastal Conservancy in 2020 indicated that the Lake Pillsbury and Van Arsdale reservoirs are generally not contaminated. Additional studies will be performed before the dams are removed, but initial information indicates mercury contamination is not a problem. Mercury is naturally occurring in California’s Coast Range, and mercury levels in reservoir sediments represented background conditions for a remote reservoir.

The upper mainstem Eel River drains the southern portion of the Mendocino National Forest, including much of the relatively high altitude Snow Mountain Wilderness Area, a drainage basin of 288 square miles (750 km2). 

There is an additional 50 square miles (130 km2) of drainage between Scott Dam and Cape Horn Dam. Scott Dam’s lack of fish passage has made tributaries in this part of the river disproportionately important for spawning and rearing, despite their modest habitat values. If access to the upper part of the watershed is restored, we expect to see less spawning in this region in the future.

Water that leaves the hydroelectric turbines is diverted into the East Branch Russian River in Potter Valley where some of it is used for agriculture before draining into Lake Mendocino. From Lake Mendocino the water is released into the Russian River watershed.

Water diverted from the Eel River to the East Branch Russian River in Potter Valley has averaged about 60 thousand acre feet per year over the last decade.

Diversions were historically much higher, but were reduced in 2006 when the National Marine Fisheries Service (NMFS) determined that continuing the diversion at historic levels would lead to the extinction of Eel River salmon and steelhead. Through most of the 20th century, diversions left only a trickle of water flowing below the dams in summer. Current water releases more closely mimic historical natural flows in the Eel River below the dams, but still result in a significant net loss of habitat.

Recently, NMFS has asked PG&E to maintain a larger cold water pool behind Scott Dam in an attempt to better control the temperature of water released to protect young steelhead in the reach between Scott and Cape Horn dams. In recent years, late summer water temperatures released from Scott Dam have been lethally high for young fish.

No. Even in drought years the upper Eel River flows year round, though it has a natural low flow season due to Northern California’s mediterranean climate. The cool, perennial tributaries above the dams are what make the headwaters important habitat for young salmon and steelhead in a changing climate. This area would provide a refuge for juvenile fish in warmer months. Currently, much of the water stored behind Scott dam is diverted to the Russian River basin. If the dams are removed, water diversions to the Russian are expected to either shift to a wetter time of year when their impacts to the Eel River will be reduced or be eliminated.

The powerhouse located in Potter Valley can generate a maximum of 9.2 megawatts, though it rarely has operated above 50% capacity in recent years. Cheaper renewable power sources continue to make the project’s hydroelectric power  less competitive than other options. For comparison, the power generated yearly by the project could be replaced by 3 acres of solar panels and at a much lower annual operating cost and with significantly fewer environmental impacts. 

In 2021, PG&E notified stakeholders that the transformer bank associated with the powerhouse failed, making power generation impossible. PG&E has not yet provided a schedule for repairing the transformer bank.

At the request of several entities, in 2017 Congressman Jared Huffman convened stakeholders in a process referred to as Congressman Jared Huffman’s Potter Valley Project Ad Hoc Committee. The stakeholder working group met in an attempt to resolve conflicts over the future of the Potter Valley Project. In these discussions, the idea of a two-basin solution emerged, which would provide Eel River fish the ability to migrate into the upper reaches of the watershed while identifying solutions that would provide Russian River interests with the Eel River water they have grown to rely on. 

In its simplest form, the two-basin solution would likely result in the removal of Scott and Cape Horn Dams and habitat restoration in exchange for continuing diversions from the Eel to the Russian River, while shifting those diversions to the wet season to reduce their environmental impact. A regional partnership formed from the ad hoc in an attempt to take over PG&E’s license for the project and pursue a project in the spirit of a Two-Basin Solution, but was unsuccessful in their efforts due to lack of funds.

Five entities working together under the banner of the Two Basin Partnership attempted to develop a win-win solution for the future of the Potter Valley Project, but were unfortunately unable to secure the necessary funding to move forward. The Partners proposed the removal of Scott Dam and modifications to Cape Horn Dam to maintain a wet season diversion while resolving fish passage problems. The Partners’ lack of success doesn’t mean that a win-win solution is off the table. It’s important now for water users to determine if it’s financially viable to secure future diversions, and develop a mechanism for funding the water supply they benefit from.

Water from the Eel River makes up only a small portion of Sonoma Water’s 600,000 customers’ total supply. Because PG&E no longer wishes to own the project, some entity would need to be responsible for the infrastructure, operations, and project maintenance to continue a water diversion. Water users continue to weigh the costs and benefits of taking over portions of the project. Upgrades will likely need to be made and funded by water users, probably coupled with more cost-effective measures like conservation and efficiency upgrades.

The Two-Basin Solution partners identified three feasible alternatives that would maintain a wet season diversion into the Russian River watershed to meet the needs of water users that have grown to rely on the water supplied by the Project. Each of the proposed alternatives would remove the substantial liability and costs of maintaining the aging dams and reduce their ecological impacts, while creating a modern water diversion structure. Water users must now determine if it’s financially viable to secure future diversions, and develop a mechanism for funding the water supply they benefit from.

The Federal Energy Regulatory Commission, also called FERC, is a federal agency that regulates energy, including electricity and hydroelectric generation from dams. All large hydroelectric dams must be licensed with FERC. Licensing comes with obligations for how dams must be maintained, operated, relicensed, and removed once they are obsolete.

The Federal Power Act requires that FERC ensure projects balance the beneficial uses of the waters affected by the dam project in question, balancing power generation, fish and wildlife protection, recreation, and other environmental concerns.

FERC typically issues licenses for 30-50 year terms. The Potter Valley Project’s  current license expired in April 2022 and PG&E has notified FERC that they will not seek a new license. PG&E recently submitted a schedule to FERC for surrendering their license for the project and proposing its decommissioning.

The Potter Valley Project is not viable as a business venture for energy production. Prior to deciding to decommission the Project, PG&E tried to sell the Project but no willing buyers stepped forward. PG&E has since said the project is unprofitable, losing $5-10 million per year in operations and maintenance costs. With no party willing to pay for the needed upgrades and continued operation of the project, PG&E will develop a plan to decommission the Project.

The owner of the Potter Valley Project, PG&E, is responsible for the facilities until FERC signs off that decommissioning of the Project is complete. This includes all costs associated with decommissioning the Project includings studies, facilities removal, potential mitigation measures and any restoration activities that are included in the decommissioning plan.

In short, no. We shouldn’t expect PG&E to do the right thing and repair the damage their dams have caused to the river. With no entity willing to take over the existing project due to its enormous costs and liabilities, PG&E will be proposing a plan for decommissioning the project. We need your help to make sure this plan includes restoring the Eel River.