I might have an idea what the cargo was.
Had a little stint doing freight brokerage the past few months and I did some loads out of Portland area hauling huge tanks up to a couple destinations in BC using that route. They were massive oversized loads but not terribly heavy. Hope none of my former carriers were involved.
It was a truck from Alberta that did it. He was hauling drilling equipment. At the bottom of this article it gives more detail LINK
I just took this road about an hour ago. At 1am with no traffic it took me about 10 minutes to do the detour. The detour goes through the middle of downtown of the city there and you have to go through about 20 lights. I had a friend who went through during the day and it took him 2 hours. It's going to be a nightmare. About 71,000 cars use that bridge every day.