Randolph Avenue meets Shepard Road in St. Paul near the banks of the Mississippi River , hemmed in by railroad tracks still serving the industrial corridor. Beyond the intersection, nearing the river, a winding network of dirt paths and pitched tents have become a makeshift neighborhood – St. Paul’s largest encampment – for hundreds of people without permanent shelter.

Posted around the site are Minnesota Pollution Control Agency (MPCA) “no trespassing” signs, many of them defaced by graffiti, warning of a stew of toxins in the soil, including lead, arsenic and mercury. The levels are so high, the signs say, that the area is listed as one of Minnesota’s permanent environmental priority sites.

The MPCA has tracked the toxins for years and has labeled the area that is now home to the encampment as a state superfund site, meaning it is eligible for state-funded cleanup.…