BC Hydro Update #4: Fraser River Transmission Infrastructure
4 p.m. July 5
VANCOUVER – BC Hydro is continuing to repair the damage caused by the fall of a 230 kilovolt transmission tower into the Fraser River, near the Port Mann Bridge in Surrey, on Monday night.
BC Hydro crews have now removed the de-energized transmission lines from the Fraser River. Additional crews from across the Lower Mainland helped to remove the line and continue to help repair damage caused to the distribution system.
BC Hydro expects a review of the incident, which will analyze the initial finding that erosion caused the damage, and repairs to the supporting transmission infrastructure will take approximately one month.
BC Hydro CEO Dave Cobb was on site earlier today and this afternoon released the following statement:
“Safety is our top priority and requires careful decision making in situations like we experienced last night and today. We immediately set out to restore power, repair the damage and re-open major roads as quickly as possible, while maintaining the safety of workers and the public.
“We thank our customers, local businesses and the residents of Surrey and Coquitlam for their extraordinary patience and understanding during this unexpected event. We also thank the RCMP, local fire departments, other emergency responders, and municipal officials for their leadership, support and cooperation throughout the night on Monday and all day Tuesday.
“We undertook extra monitoring and due diligence in recent days on both transmission towers. There was no indication that the 230 kilovolt line was at heightened risk. We will bring in external hydrology experts and engineers to help us determine with certainty the cause. We will rigorously double-check similar transmission structures that may be affected by high water levels to ensure the long-term stability of the transmission towers.”
Chronology of events
• June 11: BC Hydro discovers the tower supporting 5L44 – a 500 kilovolt (kV) transmission line – on the south side of the Fraser River had been damaged, presumably by a barge or other river traffic. BC Hydro secures the tower, begins engineering assessments of the foundation and plans for repairs.
• June 16-30: BC Hydro commences tower foundation surveys every two days to assess footings and weekly subsurface in-river stability survey.
• June 27: Temporary guying (support lines) installed on the 500 kV line. The situation is deemed stable by BC Hydro engineers.
• Thursday, June 30: The area around the 500kV tower begins showing signs of erosion. The road adjacent to the tower sloughs into the river causing the tower to drop 4 feet and shifts the tower top over 20 feet. The 500 kV line is de-energized as a precaution. A safety observer and surveyors are put on site 24/7 to monitor the situation. BC Hydro commences design for additional guying.
• June 30: CN Rail initiates installation of rip-rap (loose stone used to form a foundation for a breakwater or other structure) to rebuild the road; BC Hydro footings simultaneously receives rip-rap.
• July 2 - 4: BC Hydro conducts daily aerial surveys and an underwater survey of the neighbouring tower supporting 2L22 – a 230 kV transmission line that runs parallel to the 500kV 5L44 transmission line – and this tower’s foundation is deemed stable.
• Monday, July 4: As the Fraser River crests, there appears to have been sudden and unexpected erosion on the south side of the river, causing the 230 kV tower to fall into the Fraser River just before 9 p.m. The fall of the tower brings down additional transmission poles and infrastructure, causing tension and strain on attached lines.
• There were no injuries and no safety risk posed by the wires as protection equipment was activated when the lines toppled and they were de-energized automatically.
• About 25,000 customers in Surrey suffered a power outage. BC Hydro crews were able to respond quickly and conduct switching to restore power to most customers within 45 minutes. Power was restored to remaining customers, with the exception of a couple hundred, just after 11 p.m.
• Local authorities and emergency personnel responded to the incident and shut down Highway 1, the Lougheed Highway, the Port Mann Bridge and portions of United Boulevard in Coquitlam to ensure public safety. Marine traffic was also affected and managed by the Canadian Coast Guard.
• BC Hydro officials worked throughout the night to ensure the stability of other towers and crews worked in conjunction with emergency officials to clear the fallen infrastructure.
• Tuesday, July 5, 7 a.m.: Highway 1 and Lougheed Highway are re-opened to traffic. Crews are able to successfully remove all remaining cables that had fallen on the roads by 10 a.m.