Wise Tunnel #9 Repair

Location: Auburn, CA

Client: PG&E

A scheduled maintenance shut down required contact grouting of 480LF of voids behind an existing concrete lined tunnel. To perform the work the tunnel was shut down and drained of water. Work commenced with multiple crews scheduled 24/7 to complete the project and get the tunnel back on line by a set date.

Project challenges included placing shoring and equipment inside the tunnel and implementing detailed safety planning and training to ensure crew safety. Contingency plans were critical to account for any equipment or machinery malfunction that could impact operations and affect the schedule to place the tunnel back on line in time. With the tunnel draining into adjacent Rook Creek Lake, environmental hazards were mitigated and contingency plans put into place.

The project specifications forecast the use of 200 cubic yards of grout, with actual usage coming in at 540 cubic yards. In addition to exceeding production quantities, the project was executed ahead of schedule and the tunnel was opened and back on line 2 days earlier that scheduled.