WILMINGTON, Del. (AP) — The International Petroleum Corporation of Delaware has been sentenced to pay more than $3.5 million in fines and restitution for environmental crimes against the city of Wilmington.

The U.S. Department of Justice announced Thursday that IPC must pay $1.3 million in fines and $2.2 million in restitution to the city for operating its Wilmington facility from 1992 through 2012 without conducting the appropriate monthly samples to ensure it was dumping waste water into a local sewer at acceptable levels.

The facility processed used oil and hydrocarbon-containing waste water. Under the Clean Water Act, the company was supposed to be pre-treating and regularly testing the waste water, but IPC admitted it tampered with the monitoring methods and a Clean Water Act monitoring device.