Howard Hanson Dam releasing water for downstream needs, engineers running tests
| Howard Hanson Dam releasing water for downstream needs, engineers running tests | |
| Contact: Public Affairs Office 206-764-3750SEATTLE – The reservoir at Howard Hanson Dam reached a summer elevation of 1,167 feet above sea level in June, allowing engineers, geologists and other scientists to run a battery of tests to gather more data on the right abutment drainage improvements that are completed and underway. That testing continues as the reservoir is lowered and water is released for downstream needs.
The Corps will share results so far with national experts this month and will make a thorough review of all findings to determine prior to this November how the dam will be operated this coming flood season. 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 paths forward for 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. 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,” said the Seattle District’s Dam Safety program manager, Rob Romocki. “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, have already been completed. As of this release, the pool elevation was 1,157 feet with an inflow of 260 cubic feet per second and outflow of 340 cfs. However, flows can change in a matter of hours, dependent upon weather, so caution is advised. Flows downstream of the dam are expected to remain well below flood stage until this fall. More details and history about Howard Hanson Dam and the right abutment issue can be found at http://www.nws.usace.army.mil. |
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