Union Pacific has 100 people working around the clock this week in North Portland.
They're replacing about a mile of track inside a tunnel to Swan Island. They started the $2 million project on Friday and hope to be done before Thanksgiving.
"We’re operating 24 hours a day, seven days a week, 365 days a year," said Aaron Hunt, spokesman for Union Pacific. "Our railroad track, we really need to keep it open at all times. So when we do maintenance it’s something that we try to do in the smallest window of time possible."
Hunt said freight trains are taking detours until the work is done.