Sometimes the dirt just has a lot of radiation in it

There still isn't a definitive explanation for how the radioactive whatever got under the street. Wilma Subra's explanation sounds pretty solid, though.

Another possibility, according to Wilma Subra, a chemist and lead technical adviser for the advocacy group Louisiana Environmental Action Network, is that road fill may have contained some source of radioactivity.

“That entire area, including the university, is a (former) low-lying swampy area,” said Subra, referring to Xavier, which is just a few blocks from the site of the radiation. “That whole area is nothing but fill. That could have been a load someone brought in there and dumped in that spot."

Another theory is that someone lost a "tool" near the site with has leaked radiation since.  So maybe Thor's hammer is buried around there somewhere.

Another point to gather from this is that the radioactive hot spot is not actually on the site of the Thompson-Hayward plant but a few blocks away. It's still possible the two are related, or at least it's possible that the radiation is related to the industrial activity and/or subsequent remediation of hazardous materials in the area.  But it may be a separate matter altogether. 

Either way, a lot of people got cancer.

In testimony from a class-action lawsuit filed in 1989 against corporations that owned the plant over the years, residents said the vats overflowed and produced noxious-smelling fumes and dust. 

The suit was settled in 1996 for $51.6 million, with the money distributed among 3,800 residents and their lawyers. The money was divided based on how close a plaintiff lived to the plant and how sick they were. Cancer patients got the most money. Liver and kidney disease came next. People with afflictions like allergies and immune system issues were awarded the least.

Dorothy Travis was part of that lawsuit, as was her neighbor, Patricia Lassair, 55, who was born and raised on Lowerline Street. Lassair’s brother developed leukemia. A neighbor who she said is like a sister to her had four miscarriages. “Almost everyone around here died of cancer,” said Travis, looking out at her neighborhood from her front porch.