HOWARD HANSON DAM—Scientists have begun monitoring an abutment at Howard Hanson Dam around the clock as the annual spring storage of water in the reservoir gets underway.
The reservoir at the dam has reached 1,147 feet above sea level, the point at which the U.S. Army Corps of Engineers has to start the intensive monitoring.
The Seattle District of the Corps slowly began last month to allow water levels to rise within the reservoir.
Spring storage of water is a normal dam operation to provide summer and fall water supply.
During the pool rise, the Corps will conduct testing and in-depth investigations of the dam's right abutment, due to damage sustained last year from heavy rainfall.
Engineers say the reservoir can rise another 20 feet -- to a maximum pool elevation of 1,167 feet, unless engineers, geologists and other scientific experts on the ground see anything troubling.
If that's the case, the reservoir level can be lowered again.
The Corps is using special electromagnetic and dye tests to measure the effects of the pool on the right abutment. It will make checks much more frequently as the pool approaches that 1,167 foot mark.
Water stored during the spring refill of the reservoir is used to provide water supply to the City of Tacoma and its water supply partners.
Eighty percent of the reservoir's supply will be used for downstream flows to help endangered species of fish, including Chinook and steelhead.