Columbia-Pacific Northwest Region

Howard Prairie Dam Safety of Dams Seismic Corrective Action

As part of the Bureau of Reclamation Safety of Dams Program, Reclamation proposes to conduct modifications to the Howard Prairie Dam. This action is necessary to correct unsafe conditions and to prevent possible loss of life, property, water storage, recreation and other project purposes due to potential failure modes associated with seismic risk.

Reclamation’s Columbia-Cascades Area Office (CCAO) has authorized the Talent Irrigation District to operate and maintain the facilities in the Talent Division of the Rogue River Basin Project, including Howard Prairie Dam, Howard Prairie Delivery Canal, Hyatt Dam and Keene Creek Dam. Along with the No Action alternative, Reclamation identified the Corrective Action Study (CAS) Preferred Alternative as the Proposed Action.

• The CAS Preferred Alternative involves excavation and replacement of the existing liquefiable foundation materials with compacted fill within a portion of the downstream foundation, creating a foundation shear key.
• A stability berm would be placed on the downstream side of the dam. The density of the compacted fill would be much greater than the existing foundation materials and would eliminate the possibility of liquefaction within the treatment area.
• The foundation shear key would also include filter and drain zones and a drain pipe to provide a filtered exit for seepage through the foundation.

The purpose of the Proposed Action is to maintain the authorized Rogue River Basin Project purposes to maintain the Talent Division, while also reducing the risk of failure of the Howard Prairie Dam, thereby, reducing risk to public safety downstream to within acceptable limits established by Reclamation SOD Program.

With respect to Federal or State-listed threatened or endangered species or their habitats, the project may affect, and is not likely to adversely affect, Northern spotted owl. With respect to migratory birds, impacts would be temporary and minimized by the timing of vegetation removal avoiding take of any migratory bird, or the parts, nests, or eggs of such a bird. Approximately 5 acres of forested land would be cleared of successional evergreens and understory shrubs for staging and implementing the project.

The State Historic Preservation Officer (SHPO) concurred in June 2015 that the Howard Prairie Dam is eligible for listing in the National Register of Historic Places and the project represents an adverse effect by altering the appearance of the dam. SHPO and Reclamation are developing a memorandum of agreement toward mitigating the adverse effect that will be commensurate with the scale of the adverse effect and will be accessible as possible to the public.

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