Before there was Erin Brocavich, before there was Dark Waters, there was The Brook.  Based on actual events that happened in a small Northern town in 1988, The Brook is a fictionalized retelling of these events, where names have been changed.

Harry Bonner is the new mayor of Comptons Pond, a small
suburban town where he goes about his days officiating weddings
and attempting to solve post-election issues. But one evening after
curiosity leads him to open a locked file cabinet in his office, Harry
has no idea that what he finds inside will forever change the lives of
the people in his community, his own family included.
After a paper falls out of a binder inside the file cabinet, Harry soon
discovers that it is a proposal to clean up toxic waste in his town,
specifically at Smithfield Powder Works. With assistance from his
wife, a seasoned environmental investigator, a borough attorney, and
several environmental activists, Harry begins what quickly becomes
a perilous investigation that he hopes will help build a case against
a company with executives determined to do whatever it takes to
cover up their illegal activities, even as more citizens in Comptons
Pond become gravely ill.
The Brook is the compelling story of a small town mayor and his crew
of experts as they embark on a race against time to save their town
and its people from the tragic effects of corporate greed.