CHICAGO, Nov. 15 (Xinhua) -- The U.S. Steel Corporation has reportedly spilled toxic chromium near Lake Michigan in October and asked local environmental regulators to keep it secret.
Citing newly revealed documents, the Chicago Tribune reported on Wednesday that the 56.7 pounds (25.7 kilograms) of chromium leaked in late October by U.S. Steel's Midwest Plant in the Indiana State was 89 percent higher than relevant pollution permit.
The spill was caused by a malfunction of the plant's waste water treatment system on Oct. 25. Indiana environmental officials were notified days later, and the company asked for "confidential treatment" of the toxic leakage.
The company's spokesperson maintained that the spill wasn't serious enough to merit reporting to the National Response Center at the federal level, insisting the incident "did not pose any danger to water supply or human health."
Chicago Tribune said the Pittsburgh-based steel giant may face lawsuit for repeatedly violating the federal Clean Water Act since 2011.
In April, the same U.S. Steel plant reported another more serious spill of 346 pounds (157 kilograms) of chromium from a rusted pipe into the waterway, prompting a nearby township to temporarily shut off its Lake Michigan intake.
The City of Chicago in neighboring Illinois State also conducted emergency testing of its own water supply.
