Portland has about 2500 miles of sewer lines, and about 815 miles of them are 80 years old or more. Rather than taking a reasonable approach and regularly scheduling maintenance/repair, the city "leaders" diverted ratepayer funds toward their own pet projects; apparently in the hope that the sewer fairy would take care of the work. That approach hasn't proven entirely successful, as on occasion a break in the sewer lines will reveal itself in spectacular fashion. One line managed to erode away the substrate beneath a city street, creating a rather impressive sinkhole, as the crew of this Portland Bureau of Environmental Services truck belatedly discovered.
So it seems that there's nothing for it other than to bite the bullet and commence spending ratepayer money on the mundane stuff, like line maintnance and repair. Of course, they're so far behind the curve that crews will be able to attend to only around 2% of the backlog per year. And for this, Portland residents pay the fourth highest rates for "services" in the country.
On the plus side, ratepayer funds constructed a whole lot of bioswales and bike paths while the good times were rolling.