The Army Corps of Engineers has begun to slowly allow water levels to rise within Howard Hanson Dam’s reservoir for the annual spring fill of the reservoir. This operation mimics normal spring operations.

The corps operates the Howard Hanson Dam project, which provides flood damage reduction to the Green River valley, water flow to the Green River for environmental benefits, and water supply to the City of Tacoma and its water-supply partners.

The corps also in the planning process for testing and in-depth investigations of the dam’s current effectiveness this spring. The current draft plan is proposing to target a maximum pool elevation of 1,167 feet, which is consistent with a normal spring refill of the reservoir. However, throughout the reservoir fill, the corps would constantly monitor the operations of the facility, including special observations and tests to measure the effects of the pool on the right abutment. Because of the damage sustained to the abutment in 2009, a higher frequency of monitoring will be performed once the pool exceeds elevation 1,147 feet.

Water stored during the spring refill of the reservoir will be used to provide water supply to the City of Tacoma and its water-supply partners. Additionally, four-fifths of the reservoir’s supply will be used to bolster downstream flows to help endangered species of fish, including Chinook and steelhead. Project managers believe that the regulated downstream flows will aid spawning and other life cycle events for the fish.

More details and history about Howard Hanson Dam and the right abutment issue can be found at http://www.nws.usace.army.mil.