In Case of Emergency


Underground & Tunnels

Project Name

Poe Tunnel Liner Repair



Year Completed


Location Information

Butte County near Oroville, California

Project Sum­ma­ry

Poe Tun­nel is part of the Poe Project; com­prised of a diver­sion dam, reser­voir, and con­crete intake struc­ture along the shore of the reser­voir at the upstream end of the tun­nel and a surge tow­er, steel under­ground pen­stock, and pow­er­house at the down­stream end. The tun­nel is approx­i­mate­ly 18-feet in diam­e­ter and 6½ miles long with con­crete-lined and unlined sec­tions. The intake at Poe Dam is locat­ed in the Feath­er Riv­er Canyon at Poe Dam Reser­voir, approx­i­mate­ly 30 miles north of Oroville in Butte Coun­ty, California.

The major scope of work activities included:

  • Developing ventilation at the Poe Dam intake structure access point to pull fresh air through the tunnel,
  • Helicopter support to fly equipment, materials, supplies, fuel, and portable toilets to two remote access adits (Adits 1 and 2),
  • Cleaning debris out the three chambers of the rock trap,
  • Repairing cracks in the existing concrete tunnel liner, including temporary shoring and scaffolding,
  • Installing ten 1-inch diameter threaded bar anchors in the tunnel invert at the crack repair area (where it was observed to be lifting) to prevent further movement,
  • Exposing the existing drain valve at Adit 1 and cleaning out the debris from the pipe to determine if the valve is operable, and
  • Pumping grout into cracks in the concrete liner, along the invert of the tunnel, to fill voids where underlying material had washed away.

Key Chal­lenges

The repair work was per­formed dur­ing a planned out­age and was con­duct­ed in strict accor­dance with Cal/​OSHA – Title 8, Tun­nel Safe­ty Orders, due to the lim­it­ed access from the intake and through the two remote adits.