OROVILLE, Calif. — Pacific Gas and Electric Company (PG&E) is preparing to permanently re-route its electric transmission lines to be farther away from the Oroville Dam auxiliary spillway.
“Repositioning the transmission lines will ensure they are clear of the dam’s auxiliary spillway should it ever be used again. This is a good time of year to do the work as demand for power is lower now than in summer, so briefly taking the line out of service means little impact to the power grid. We aim to complete this work as safely as possible, and continue to provide reliable service to our customers,” said Eric Back, Senior Director of Transmission Lines.
PG&E crews and contractors us helicopters to install five temporary steel poles on Monday. The power lines will be temporarily relocated to the poles so that two towers can be removed and later new steel towers can be set to shift the transmission line further west and completely clear of the auxiliary spillway.
PG&E will have a helicopter staging area on the west side of the Thermalito Diversion Pool north of the diversion dam and near a law enforcement shooting range, which will be closed while PG&E flies five steel poles and equipment.
In May and June, crews will remove two steel lattice towers and clear a new right-of-way for the line. PG&E will then install eight permanent steel towers and re-route the transmission line, again using helicopters and the staging area. The new towers will be about 1,800 feet west of the previous transmission lines, which predate the dam.
On February 10, the day before the auxiliary spillway was first used, PG&E de-energized and removed power lines from three transmission towers that were in or near the auxiliary spillway path. This was done to prevent any towers compromised by spillway flows from pulling on adjacent towers. The towers were not impacted by the auxiliary spillway flows and were removed after the evacuation order was downgraded.
Once the evacuation order was lifted, PG&E built a “shoo-fly,” or temporary re-routing of the power lines, by installing wooden poles west of the old power lines and returned the transmission line to service.
The state Department of Water Resources, which owns the Oroville Dam and its Hyatt Powerhouse, has its own electric transmission lines which carry power generated at the powerhouse to a PG&E substation in Oroville.