On August 8, a severe electrical malfunction at the Tukwila traction power substation caused extensive damage to the unit, according to Paul Denison, director of light rail operations at Sound Transit. Following the outage, drivers were given orders to slow acceleration.

Briefing board members Thursday during the Operations and Administration Committee meeting, Denison said an error during installation caused the electrical failure.

“We found the root cause of the failure and it was because of some loose fasteners on one of the busbars,” Denison said. “It appears when that busbar was installed that those fasteners were not properly tightened.”

According to Wikipedia, a busbar is “a strip of metal used to conduct electricity within an electrical substation, distribution board, electric switchboard or other electrical equipment.”

“It looks like it was a one-off unfortunate event that was missed during the install by the contractor,” Denison said. Sound Transit was not able to provide the contractor’s name, or any plans to recover the cost, by press time.

Denison said Sound Transit has proactively examined the other substations in the system, but ST workers cannot easily access these fasteners. To do so, the entire back wall of the substation must be taken apart. So instead, Sound Transit used an infrared camera to determine if the other busbars were producing any additional heat.

“We have not found any other issues to date,” Denison added. “We are going to take some lessons learned and we are going to set up our substations, more than likely, so we will have some access to the back of the substations going forward.”

On September 12, Peter Rogoff, CEO of Sound Transit, declared the repairs an emergency due to the lack of a back-up to the substation.

“If either of the adjoining substations were to fail, a complete of loss of power to Link could occur between the Rainier Beach and Angle Lake stations,” Denison told the committee.

He said the nature of the failure and the complexity of necessary repairs exceeds the capacity of the current staff, requiring an outside contractor. The committee pushed through a motion recommending the full board approve a $300,000 repair services contract between Sound Transit and Siemens Industry, Inc.

Denison said the $300,000 figure was estimated before Sound Transit understood the extent of the damage and the repair is expected to exceed that amount. He said an additional $300,000 has been placed into Sound Transit’s budget for next year, but can’t be drawn down without board approval.

Denison said once the work is completed Siemens will provide a 12-month warranty on the components, material and workmanship of the repairs.