Scientists are planning to dig at least a dozen holes in the ground and send the contents out for lab tests.
It could take up to two weeks to get the results.
"I'm just here really to look at the current conditions, where it is right now and to see if we could pinpoint a potential source to that groundwater contamination," said Bruce Everetts, Illinois EPA.
The contaminated well was sealed in March. Crestwood officials have said they used the well only to supplement the town's drinking supply and there was never any public health danger.