Owyhee Dam, Across Owyhee River, Nyssa, Malheur County, OR

Significance: Owyhee Dam is a 417-foot-high, concrete thick-arch dam (or arch/gravity dam). At its completion in 1932, Owyhee was the tallest dam in the world, a short-lived distinction because it was superceded in 1936 with the completion of 726-foot high Hoover Dam. Owyhee Dam has engineering significance as the proving ground for construction techniques developed by Bureau of Reclamation engineers for use at Hoover Dam. Tests conducted on the cooling and shrinking of mass concrete as it cured at Owyhee Dam helped assure Bureau engineers that their techniques would work at Hoover Dam. Historic apparatus for monitoring those tests is still in place on the interior of Owyhee Dam. Owyhee also has engineering significance for its ancillary features. The ring gate on the Owyhee Dam spillway was the first ever built. It was the first dam in which a freight elevator was installed. The needle valves in the outlet works for Owyhee Dam, which make it possible to regulate the discharge of water under very high pressure, represent a late stage in the evolution of such valves by the Bureau of Reclamation. Upon its completion, Owyhee Dam began storing water for use by farmers on the Owyhee Project, one of the most important in the development of irrigated agriculture in Oregon.
Survey number: HAER OR-17
Building/structure dates: 1932 Initial Construction
Building/structure dates: 1984 Subsequent Work