The city of Chicago and a surfing organization have told a judge that a proposed federal settlement over U.S. Steel's repeated chemical spills into Lake Michigan is inadequate.

The Chicago Law Department and the Surfrider Foundation urged the federal judge Thursday to impose tougher penalties on the steelmaker for last year's hexavalent chromium discharges from its Midwest Plant in Portage, Indiana, into the region's primary source of drinking water, the Chicago Tribune reported.

The nearly $900,000 in fines and penalties proposed by the federal government fall short when compared with the ecological damage caused by the carcinogenic discharges, according to court documents filed by the city of Chicago and the nonprofit foundation. The settlement also requires the steelmaker to test for hexavalent chromium daily, create a preventative maintenance program and upgrade all pollution monitoring.

"The government's inadequate oversight ... demonstrates the need for Surfrider to remain vigilant," said Mark Templeton, the group's attorney.

The University of Chicago's Abrams Environmental Law Clinic discovered last year that the manufacturing and finishing plant had violated chromium limits in its federal water pollution permit at least four times since 2013. The plant's chromium discharges are limited to 30 pounds a day, while hexavalent chromium is limited to about half a pound a day.