Replica helps plan California dam fixes
Utah researchers watch water rush over model
LOGAN, Utah — Inside a cavernous northern Utah warehouse, hydraulic engineers send water rushing down a replica of a dam built out of wood, concrete and steel — trying to pinpoint what repairs will work best at the tallest dam in the U.S for a spillway torn apart in February during heavy rains that triggered the evacuation of 200,000 people living downstream.
The sound of rushing water is deafening as Utah State University hydraulics engineering professor Michael Johnson kneels in front of the Oroville Dam replica the size of a small house to examine one of two channels that run the width of the spillway to allow air into the water to prevent bubble formations that can damage the concrete spillway of the real dam.
The new channels, called aerators, are one of the key features in the proposed $300 million spillway reconstruction set to be completed by November.
While a separate team of dam experts tries to solve the mystery of why the spillway crumbled last February, the hydrologists who built the replica are using it to guide California authorities on how they should build a new spillway so that it can withstand rushing waters.
Besides confirming that the channels to aerate water going down the spillway would ease pressure on it, the Utah testing has determined that an adjustment to a curve about halfway down the spillway would only slightly improve its effectiveness. The idea was to make the curve more gradual near a steep part of the spillway where it caved in and left a gaping hole the size of a football field in the concrete chute.
Though computer modeling is being used extensively to plan the spillway repairs, California officials and the hydrologists say high tech testing is no replacement for dam replica research. Johnson’s team has a $277,000 contract for the work and will issue its final report in the early fall.