Floods and Flooding

Plan to raise Arrowrock Dam fails federal feasibility study

Hopes of Idaho officials to increase the height of a Boise River dam to double water storage and also create enough space to handle a 500-year flood ran aground after the project failed a federal feasibility study.

The U.S. Army Corps of Engineers told the Idaho Water Resource Board on Wednesday that the $1.26 billion cost of raising century-old Arrowrock Dam 70 feet outweighed the benefits, killing the project.

The board absorbed a second blow shortly after when U.S. Bureau of Reclamation officials said the federal agency will need $1.75 million in cost sharing to study a much less ambitious plan costing an estimated $31 million to raise Anderson Ranch Dam 6 feet.