The commanding general of the U.S. Army Corps of Engineers told U.S. Sen. Patty Murray (D-Wash.) Thursday in Washington D.C., that design alternatives for a permanent fix to a leaky right abutment next to the Howard Hanson Dam would be ready by June.
Murray, a senior member of the Senate Energy and Water Committee, pressed Lt. Gen. Robert Van Antwerp, commanding general of the corps, about plans to fix the dam, according to a media release from Murray’s office.
Murray pushed Van Antwerp to assure her that the corps is doing everything possible to meet the critical June deadline for completion of a study to come up with a permanent fix to the dam that helps protect the Green River Valley from flooding.
Unless this study is completed on time, Murray said the project will not be eligible for fiscal year 2012 construction funding.
Van Antwerp told Murray that the study would be ready.
“The study will be at the point that we will have alternatives identified that we can start with design, so that we can begin the process of the design,” Van Antwerp said.
Murray thanked Van Antwerp for his recent visit to the dam to see first hand the importance of fixing the leak.
“Thank you so much for your work on the advance measures for the Howard Hanson Dam as well as for coming out to visit the site,” Murray said. “I would like to continue working with you to find ways to move forward on this process as quickly and safely as possible.”
The corps constructed a grout curtain last fall as a temporary fix to the leak, but still could not store as much water as normal in the reservoir behind the dam.
A permanent fix, which could mean construction of a concrete cutoff wall, is expected to take three to five years to complete.
The abutment was formed nearly 10,000 years ago by a landslide. The federal government built the rock-and earth-fill Hanson dam in 1961 next to the abutment to control major flooding in the Green River Valley. The dam is about 25 miles east of Kent.
Problems with water storage behind the dam were discovered by the corps when a 10-foot-wide depression formed on the abutment next to the dam after heavy rain in January 2009.
The cities of Kent, Auburn and Tukwila placed giant sandbags along the Green River levees last fall to help protect against flooding. There has been no flooding this winter along the river because of the mild weather with no heavy rainfall.
The corps earlier this month began to slowly allow water levels to rise within the dam’s reservoir for the annual spring fill of the reservoir. This operation mimics normal spring operations.
The corps operates the dam for flood control during the winter as well as to provide water supply to the City of Tacoma and its water-supply partners, including Kent.
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 proposes 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 of 1,147 feet.
