Expert Witness Blog
Army Corps of Engineers officials said Tuesday that water is flowing through the 48-year-old Howard Hanson Dam’s right abutment “very fast” and may mean the earth-and-rock structure could erode if too much water is stored behind the dam. By November the Corps will install a “grout curtain” to reduce seepage and will drill more vertical and horizontal drains 32 miles upstream from Auburn, WA, at a cost of over $20 million.
Planning will then begin on a permanent solution, which is likely several years away. Hydrology and dam safety experts from around the country are advising the Corps on those interim measures and possible long-term solutions. The speed at which water is seeping through a flank of the Howard Hanson Dam has, by one key measure, increased since January, and the people who operate the dam don’t know why.
Excerpted from TheSeattleTimes.com.