BC Hydro stabilizing de-energized 500-kilovolt tower near Port Mann Bridge
BC Hydro will be using a low flying helicopter this afternoon as part of the work to install a guy wire (support wire) between the leaning 500 kilovolt transmission tower near the south side of the Port Mann Bridge and the next closest inland tower 1,743 feet away. This work will further stabilize the 500 kilovolt tower. Its foundation was damaged in mid-June and was further destabilized by the same erosion that ultimately led to the fall of a 230 kilovolt transmission tower into the Fraser River on Monday, July 4.
The power lines on the tower remain de-energized and 18 barge loads (about 20,000 tons) of riprap continues to be placed around the tower and along the adjacent downstream road to further stabilize the foundation and bank against erosion.
Editor’s note: Media access is not possible from the south side of the Fraser River or from the water given that this is an active work site and the area near the work site will have controlled marine access. BC Hydro will be collecting video footage and still photographs that will be made available to media as early as possible this afternoon at www.bchydro.com/mediabulletins.
At approximately 12:25 p.m. today, an additional guy wire (support wire) will be installed between the damaged 500 kilovolt tower and the dead-end tower to its immediate south to provide even more stability to the system. This work will be done by BC Hydro crews starting in a helicopter that will fly a rope between the two towers in order to accommodate space constraints due to the location of the towers in the CN Rail yard and at the side of the river. The rope will then be used to pull the guy wire which will then be secured by BC Hydro crews accessing the towers with bucket trucks. On Wednesday, BC Hydro crews will complete the work by adjusting tension on the newly installed guy wire.
In the coming weeks, BC Hydro will finalize the permanent solution for repairing and re-energizing both the 230 and the 500 kilovolt systems. This decision will be based on a number of engineering and geotechnical studies by both BC Hydro engineers and external experts.
For the past three weeks, BC Hydro crews have been working around the clock to continue to increase the stability of the north and south towers (see attached map). These steps have included:
- Stabilizing the de-energized 500-kilovolt tower on the south side by placing riprap (loose rocks and boulders) in the most vulnerable areas around the tower and along the riverbed.
- Taking measures to prevent continued sloughing at CN’s dike and road adjacent to the 500-kilovolt tower by burying the fallen 230-kilovolt tower-- which is submerged in the water alongside the dyke and road -- with riprap rather than salvaging the fallen tower from the river;
- Attaching additional guy-wires (support wires) from the ground to the waist (half way down the towers) of both the north and south towers.
- Lowering the de-energized conductors (power lines) from the tops of the two northern towers to approximately half way down the tower (waists).
- Continued around-the-clock monitoring and assessment.