should have been prevented. There is no way that officials in Michigan could not have known that the Flint River was polluted, or been able to do appropriate feasibility studies to determine if that water even could be treated adequately to be safe for drinking. But this particular story has an even uglier facet to it--Flint isn't alone.
Actually, a lot of communities have drinking water that is substandard or at-risk. Vox has found that there is lead poisoning in communities throughout the country. And it shouldn't be a surprise that a lot of the communities that have contaminated water are poorer communities--they are all-around more exposed to contamination, and remediation of pollution is expensive.
But lead isn't the only contaminant--there's pathogens (like the E.coli and Legionnaire's disease that may also be contaminating Flint's water), arsenic, radon and more. Some contamination is very area-specific, like the uranium in the groundwater used by thousands of Navajo nation people, or areas whose water can be jeopardized by coal ash spills.
So while the crisis in Flint is the most visible story about unsafe drinking water, and one of the more egregious cases of how the people there came to be drinking poison, keep in mind that people in St. Joseph, LA and Firebaugh, CA also have water they simply can not trust. And while there are ways to fix the infrastructure to provide these people with safe water--the resources to do it are not to be had locally, and this dynamic perpetuates poor health outcomes.