The Howard A. Hanson Dam is part of the Green River Watershed, and the reservoir created by the dam provides water for the city of Tacoma. An unusually high amount of rainfall hit the watershed in January 2009 causing water to seep through the dam’s right abutment more rapidly than usual. This revealed a troubling structural weakness. The Army Corps of Engineers responded by immediately drawing down the water levels to release pressure and injecting grout into the abutment to slow the leakage, but that didn’t solve the problem.
To prevent further, serious damage, the Corps will prevent the reservoir from reaching its maximum capacity this flood season by releasing excess water into the Green River. Unfortunately, a particularly stormy season could cause more water to be released than the river can manage safely. If severe flooding occurs, over 25,000 people from Auburn, Tukwila, Kent, and Renton may have to evacuate, and millions, perhaps billions, of dollars in damages could occur. The likelihood of this catastrophe coming to fruition is entirely dependent on the weather, so it’s safest to prepare for the worst well before an actual emergency.
Check out Emicus’ Howard Hanson Dam section to keep up with the latest developments regarding the dam.
This post is in: News & Alerts