"Defense industrial complex pollutes town then pretends they didn't despite everyone dropping dead from cancer" is a tempting and juicy narrative and will generally be welcomed with open arms around here even if it turns out reality is a lot more mundane (reality is almost always more mundane than the story).
This does not appear to be an example of corporate bad behavior because it is lacking in both negligence and malice.
If you want to be outraged over evil corporations go read about DuPont poisoning the water in various places. There's been a few longer articles posted here about it fairly recently and they seem to actually be acting in bad faith.
It's really easy to sit in an air conditioned office in 2019 and look at decisions made decades ago and say "they should have known" when in in all liklihood the people doing this probably didn't know they were leaving behind an unsafe level of radioactivity.
Speaking generally about pollution, not this specific case, everybody wants to see everything as the result of some bad actor(s) so they can have someone to blame. Reality is often much more mundane. Usually either it was not widely known that the thing was dangerous at that level of exposure, the people who could know didn't want to go looking for the knowledge or society considered the pollution worth it and if it bothered you the onus was on you to limit your own exposure (social media comparison anyone?). If you didn't want to smell paint all day you didn't live downwind of the paint factory. Times have changed a lot and to try and look at decisions in the past through the lens of modern values is a fools errand, to put it charitably.