Oroville Dam River Outlet Diversion Tunnel No. 2

Under emergency contract, Syblon Reid was selected to rapidly and surgically remove a deteriorating baffle ring within the river outlet tunnel at the Oroville Lake Dam.

The baffle ring was located approximately a ½ mile inside the outlet tunnel underneath Lake Oroville. Syblon Reid followed strict Cal/OSHA – Title 8, Tunnel Safety Orders as well as all necessary confined space requirements due to the use of heavy equipment within the tunnel.

Responding in short order, Syblon Reid mobilized and began by first establishing ventilation utilizing over 1½ miles of dam galleries to provide a safe and adequate air supply for the workers within the confined space of the tunnel. The baffle ring was constructed of a trapezoidal concrete ring lined with a T1 steel plate around the circumference of the 35-foot diameter tunnel. The baffle ring and tunnel were half submerged throughout the project requiring Syblon Reid to use barges and floating platforms in order to complete the job. Additionally, a team of specialized divers was brought in to perform the underwater tasks. All work had to be accomplished within a critical 10-day outage period.

Syblon Reid worked around the clock from atop a 120-foot x 30-foot floating platform to remove 60 cubic yards of concrete. The concrete above the waterline was chipped out and dropped directly onto the platform. Submerged concrete sections had to be chipped out and placed by the divers into buckets lowered beneath the water so the material could be lifted out and placed onto the platform. The barge would then move the platform out of the tunnel to a location where the concrete could be disposed of. Additionally, the steel band that encircled the tunnel had to be cut out and removed.

Once all concrete and steel were removed, the tunnel liner was repaired. In addition to removal of the baffle ring, Syblon Reid built and installed a new pressure relief wall to protect the powerhouse from catastrophic failure of the low level outlet valves. All critical work was completed within the 10-day outage period without a single loss time accident or OSHA recordable incident.

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