During the dismantling of Gold Ray Dam, a 106-year-old timber cofferdam and 70-year-old concrete dam near Medford, Ore., the Rogue River blew through a sand spit, changed course and ran freely for the first time in more than a century.
Scott Wright, project manager for the Corvallis, Ore., office of design-build contractor River Design Group, says the entire process actually sped up the crew’s work by almost two weeks.
Crews built two temporary sand-and-gravel cofferdams—one in the river and one in the adjacent peninsula, Tolo Slough—to ease the removal of the permanent structures. In mid-August, as crews started tearing out one of the temporary dams to let the river run through a section of the removed concrete dam, an upstream sand peninsula tied into the temporary structure developed a leak. Crews tried to plug it with sand and gravel, but “eventually it started to pipe too much material in there and created a break,” Wright says.
That break grew and sent the river rushing through the sand and the portion of the dam that had been removed, temporarily stranding equipment.
Jim Vial, Jackson County roads and parks manager, says that while completely unexpected, the revised procedure worked out. “Once we determined it was okay, we said, ‘Let it rip now,’ ” he says.
Using standard track-hoes mounted with picks and crushers, crews finished removing the 18-in.-thick, 38-ft-tall concrete dam in less than two weeks.
Crews plan to remove the 106-year-old, 3-ft-thick, 34-ft-high log dam by breaking up old concrete and yanking out the logs, which will be reused.