The Washington Department of Transportation estimates repair work on the cable will be finished on Saturday, but the question of who will pay the hundreds of thousands of dollars to repair it is still under investigation.
WSDOT officials still don't know exactly what hit the steel anchor cable, which was one of two cables holding the far west pontoon on the 520 Bridge in place.
"Something big hit it," said WSDOT's Dave McCormick.
From a picture of the broken cable, officials know whatever hit it was something significant.
"I don't know what would have done it or could have done it. I mean, it had to be substantial," said Rick Rodda of WSDOT's bridge maintenance team.
They also know roughly when the cable was broken because maintenance workers had been in that pontoon just two to three weeks earlier and found nothing out of place.
Then, four days ago, they noticed strands of the steel cable coming into the pontoon and saw the cable hanging straight down over the side of the pontoon.
"They were all coming undone," Rodda said. "Everything should have been tight, so they knew right away we had a rat's nest down there. Something had clipped it."
WSDOT is working with contractor Kiewit-General-Manson on the repairs, which began on Friday. They're now running new steel cable from the anchor on the lake bed up to the inside of the pontoon.
All that remains now is the question of who is responsible for the damage.
The area is near a throughway for vessel traffic, and Kiewit has constructed barges in the area while working on the new 520 Bridge.
"We're working with the contractor to try to establish where their vessels were and what they were doing over the last few weeks here," McCormick said.
One thing they're certain of is that the cable was nearly new and had passed inspection just last April. McCormick said it did not break on its own.
"This cable was in the best condition that they rate it," he said.
The Coast Guard expects to receive WSDOT's report on Monday. They'll look for two things: One, if someone ignored the marine safety rules and caused the damage, and two, if someone failed to report a vessel strike. In either case, the Coast Guard could issue penalties.
In the end, the responsible party will have to foot the bill for repairs.