Cascade Island (North Bonneville, Washington)

 island  Add category

 Upload a photo

The Bonneville Dam is a hydroelectric dam completed in 1938 and located on the Columbia River at River Mile (RM) 146. The dam complex is built across three islands - Robins, Bradford, and Cascade. When the dam construction began the Columbia River was split only by Bradford Island. As the dam went in the Spillway Dam was built between the Washington shore and the north side of Bradford Island; the powerhouse was built between the south side of Bradford Island and the north side of a newly created island named "Robins Island"; and the locks were built on the south side of Robins Island and the Oregon shore. In 1982 a second powerhouse, called the "North Powerhouse", was built. The Columbia River was re-routed and Cascade Island was created, with the North Powerhouse being built between the north side of Cascade Island and the Washington shore. The Spillway Dam was now anchored on the south shore of Cascade Island.

Cascade Island was built during constrution of the second powerhouse, now known as the "North Powerhouse". The North Powerhouse lies on Cascade Island north shore and the original Spillway Dam lies on the islands south shore.