Rio Dell's Water Security at Risk: Impacts of Potter Valley Project's Decommissioning

Strategic Insights -

The City of Rio Dell, California has submitted a document to the Federal Energy Regulatory Commission (FERC) regarding the decommissioning of the Scott Dam, a part of the Potter Valley Project (P-77). The removal of the dam, which has been announced since 2018, poses significant risks to Rio Dell's water security, systems, sustainability, and overall water quality management.

Key Takeaways:

  • The Potter Valley Project, constructed in 1905, diverts Eel River water to the Russian River watershed through Scott Dam and Cape Horn Dam, affecting Rio Dell's water security and long-term sustainability.
  • The removal of Scott Dam will restore natural flow patterns, characterized by higher winter/spring flows and potentially lower summer/fall flows, which may require operational adaptations for Rio Dell's water infiltration system.
  • Approximately 40 million cubic yards of accumulated sediment will be released during the removal process, presenting immediate and long-term considerations, including changes in flow channelization, increased river turbidity, and potential clogging of infiltration galleries and wells.
  • Rio Dell's junior water rights status leaves the community vulnerable during any water shortage periods, and the removal of the Scott Dam increases this vulnerability.
  • The city's economic situation reflects broader challenges facing small rural communities in Northern California, with below-average incomes, higher-than-national poverty rates, and limited economic diversity.
  • Potential solutions to mitigate negative consequences include:

+ Funding the design and construction of an extension to the Rio Dell infiltration Gallery to cross the span between both west and east banks.

+ Funding the design and construction of a flocculation/sedimentation basin at the water treatment facility to reduce turbidity and improve water processing.

+ Funding the design and construction of an enhanced water backup well system.

+ Conducting a comprehensive study of mercury in lakebed soils.

+ Funding ongoing mercury monitoring along the Eel River, both during the deconstruction phase and for an appropriate period of years or decades following decommissioning.

+ Expropriating a reasonable portion of existing senior water rights to the City of Rio Dell in anticipation of the increase in variability in seasonal water flows.

Statistics:

  • 40 million cubic yards of accumulated sediment will be released during the removal process.
  • Rio Dell's median household income is $46,055, approximately 48% of California's median household income of $96,334.
  • Per capita income in Rio Dell is $24,427, which is below the state average.
  • The City of Rio Dell has a poverty rate of 13.5%, higher than the state average.
  • During the 2014 drought, Rio Dell residents reduced water use by 56 percent.

Sources:

  • City of Rio Dell. (2023). Letter to the Federal Energy Regulatory Commission regarding the decommissioning of the Scott Dam.
  • State Water Resources Control Board. (2014). June 30 curtailment notice for Rio Dell.
  • City of Rio Dell. (2018). City Council meeting minutes, November 6, 2018.
  • City of Rio Dell. (2019). City Council meeting minutes, September 17, 2019.