This all depends on what standard of living your inhabitants want.
I mean are they going to watch TV? Turn on their lights? Eat canned food? Read Stack Exchange?
You have about 2 and a half million people living in Portland and the surrounding area. That's a huge amount of food, energy, and waste to deal with.
Do you have energy generation for that many people?
Waste disposal and sewerage is probably fine as that's already distributed although it does depend on where your treatment plants are.
Water supplies? That depends on whether the reservoirs are in your area. The taps may run dry.
Food you may be able to grow enough to live on if you have enough farm area. The diet is going to be much reduced in variety though as you lose all imported foods.
The problem you have is that the modern would is so inter-connected and everything depends on everything else. Your factories are going to shut down as they can't get components they need, and they can't sell their products to enough people. With all the people out of work there no longer spending money the rest of the economy also collapses.
Equipment is going to break down as you can't get spare parts. Do you make any cars in Portland? If not everyone is going to be walking soon.
Do you have oil wells or other sources of fossil fuels and the refinery to process them? If not people are going to be walking even sooner.
The good news is that with 90% of your population unemployed and no power for heating or food to eat that 90% are all going to die. The remaining 10% can then settle down to a simple agrarian subsistence farming existence that will let them survive for a while.