A study ordered by Congress finds higher natural gas costs and electricity demand in California have greatly increased the potential benefits of building multi-purpose Auburn Dam with up to 800 MW of hydropower.
The Bureau of Reclamation began construction of Auburn Dam, formally called the Auburn-Folsom South Unit, in 1967. However, work was suspended in 1979 in reaction to a 1975 earthquake, 50 miles away, that measured 5.7 on the Richter scale. Excavation and foundation preparation had been substantially completed, 40 miles northeast of Sacramento on the American River.
In 2005, Congress authorized BuRec to update the cost analysis for the project to determine whether a full feasibility study is warranted. (HNN 11/23/05) The study was to identify: project features that are still relevant; changes in benefit values from previously analyses; and design standard changes required to update a 1978 BuRec design.
Annual hydro benefits could total $113 million
The new report said an increase in the cost of natural gas and other alternative energy sources, combined with increased electricity demand, boosts Auburn Dam’s hydropower benefits by up to $106 million a year more than its 1963 benefits.
Based upon various assumptions, the analysis indicates annualized hydropower benefits could range from $53 million to $113 million. A 1963 report identified $6.6 million in annual benefits from hydro.
Hydropower benefits calculated in the 1963 report were based on a 240-MW power plant; authorizing legislation allowed for an eventual increase to 400 MW. Various project capacities have been mentioned over the years, including a 750-MW power plant, and a 300-MW plant that could be expanded to 600 MW.
Benefits calculated for the new report are based on an 800-MW hydropower plant versus the annual cost of building and operating an equivalent-sized natural gas power plant.
The report, released in January, identifies changes in design standards from 1978, assesses risks and uncertainties associated with that design, and recalculates the cost of the design to current dollars.
The analysis indicated the cost of designing and constructing Auburn Dam is significantly higher than in previous analyses. Depending on assumptions made, total project costs could range from $6 billion to nearly $10 billion. Construction costs would include $2.1 billion for a concrete gravity dam and $578 million for a hydroelectric plant.
Report cites evolution of design criteria for dams
The 1975 earthquake, which occurred near Oroville Dam (HNN 2/23/07), raised concerns about the safety of dams such as the thin-arch concrete dam proposed for the Auburn site. A seismic hazard analysis led to re-evaluation of the type of dam to be built.
The new report concluded the 1978 design likely would never be built. It notes design criteria for dams and other water control structures have changed dramatically since the 1970s, especially in the hydrologic and seismic disciplines.
Additionally, the evolution of dam design over the last 30 years has led to a greater understanding of physical processes, and technology has opened many possibilities for materials and construction methodologies not available in the late 1970s.
Auburn-Folsom South Unit was proposed to: provide a supplemental water supply for irrigation, municipalities, and industry; alleviate depleted groundwater; generate hydropower; and increase fish protection. It also was to provide additional recreation opportunities and increased flood protection when combined with the 198.72-MW Folsom Dam and reservoir downstream. (HNN 2/7/07)