Most power plants were designed with 30 year life spans. With “life extension” work, they can reach 50 years. But many of the oldest plants had lousy heat rates (BTU consumed to make a kWh of electricity) and weren’t really economically viable. The only reason they were kept running was because all the government regs made it so damned hard to build anything new anywhere...including on the same property as the old plant.
When a plant is shuttered, the fly ash storage area must be cleaned up.
I have a friend who drives a truck and has been making two drips daily from the plant to the disposal site, approximately 400 miles. He has been doing this for about three years, and has at least 4 more years left on this job.
This was a viable plant. Not a big producer, but ran during peaks. Wasn’t worth it to upgrade to the new EPA pollution control requirements.