Engineers, geologists and other scientists continue to run a battery of tests on the right abutment drainage improvements at the Howard Hanson Dam.
The reservoir at the dam along the Green River reached a summer elevation of 1,167 feet in June to allow for more tests at the abutment, which was damaged by a storm in January 2009. That testing continues as the reservoir is lowered and water is released for downstream needs, according to a U.S. Army Corps of Engineers media release.
The Corps plans to release results of those tests and a review of the findings before November as officials determine whether the dam can operate at full capacity this winter.
The dam helps protect Kent, Auburn, Renton and Tukwila from flooding.
The Corps is measuring seepage rates through the abutment, testing functionality of the new drains, as well as conducting other investigations during the next couple of weeks. That data then will be analyzed. The results of that data analysis will help determine any further interim measures, as well as any potential long-term repairs, to reduce the flood risk in the highly populated cities of Auburn, Kent, Renton and Tukwila and unincorporated King County.
“As construction on the drainage improvement work continues, all indications are that the new measures will perform as intended,” said Rob Romocki, the Seattle District’s dam safety program manager for the Corps. “Once the current improvement work has been fully completed, we will evaluate the effectiveness of those measures and determine to what level we will be able to hold a flood pool this coming flood season. We need to look at all the data from this summer’s conservation pool and analyze what we see before a decision can be made on how to safely operate the dam next flood season.”
Drainage improvement work is on schedule and is expected to be complete by the end of October. Drains through the area of highest concern, known as the short path seepage area, already have been completed.
For more information about Howard Hanson Dam and the right abutment issue, go to www.nws.usace.army.mil.
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