BP spokesperson Christina Audisho said Tuesday that “the Whiting Refinery is back to normal operations" at the site along Lake Michigan some 15 miles southeast of Chicago.

These are old wells that could be leaking oil, natural gas, or salt water into the environment potentially polluting public drinking water supplies, harming livestock, and impeding agriculture and other land uses.

Oil refineries emit benzene a chemical that can cause cancer and other health problems. From 2018 to 2021, 25 oil refineries in the U.S. had high levels of benzene at their fence lines for more than two weeks after the plants should have taken action to lower them.