The Indiana Department of Environmental Management (IDEM) on Wednesday set new mercury discharge limits for BP’s massive Whiting, Indiana refinery located just outside Chicago.

The stricter limits will force BP to reduce its mercury discharges into the lake every year by about one-third.

Under the current rules, BP’s mercury discharges must not exceed 23 parts per trillion. The new guidelines reduce that amount to 8.75 parts per trillion. It will go into effect on Nov. 1.

“It’s a significant drop but the technology exists for them to do it,” IDEM spokesman Dan Goldblatt told WBEZ today.

BP spokesman Scott Dean countered that the technology IDEM is talking about hasn’t been tested in the real world.

“These technologies are promising but we do need to see how they work year round in a variety of weather and operating conditions,” Dean told WBEZ. “This is a very, very challenging permit limit and it could be difficult to meet but we’re going to try our best.”

The new technologies were developed by BP in collaboration with the Argonne National Labs in suburban Chicago and the Water Institute at Purdue University Calumet in Hammond.

IDEM is actually forcing BP to work with the entities to make sure its mercury discharges comply with the Clean Water Act.

The effort came about in 2007 after BP announced its $4 billion modernization of the century-old Whiting Refinery in order to process heavier and dirtier Canadian crude oil.

A public outcry from Chicago politicians and environmental groups followed when it came out that BP’s mercury discharges would exceed federal limits.

Since then, BP says it will continue to “try” to meet the reduced limits.

“BP is committed to protecting Lake Michigan and we are cautiously optimistic that our recent investment in new water treatment equipment will further reduce the Whiting Refinery mercury discharge,” Dean said. “Having said that, the mercury limit in the revised permit has decreased by more than half and the refinery needs to gain experience operating the new equipment before we will know if the refinery can successfully and consistently meet this revised limit.

But Goldblatt says there is no trying.

“They can say they’ll try all they want, they will have to meet it,” Goldblatt said. “If not, they’ll be in violation of the Clean Water Act.

He continued, “Fines are always an option.”

Goldblatt declined to say how much the fines would amount to.

Ann Alexander, lead attorney for the Natural Resources Defense Council in Chicago, gives IDEM credit for getting tough on BP, something it hasn’t always done in the past.

“The new permit is somewhat of a pleasant surprise, albeit still a mixed bag.  While IDEM did not do everything we asked here, it adopted some of our key requests, and made modest but significant changes. Overall, the language of the agency’s response to our comments reflects a newfound spirit of willingness to take our input seriously,” Alexander said in a written statement.

Alexander says IDEM should require BP to use the developing technology. She also takes issue with the way mercury discharge from the refinery is actually calculated .

“The State of Indiana must address the health and well-being of Hoosiers and those of us in neighboring states impacted by the potential for wholesale dumping of toxins into the source of drinking water for millions,” Alexander stated. “While we remain deeply concerned that the tar sands expansion at the Whiting refinery has happened at all, these small steps in the right direction by IDEM affords some cautious optimism that environmental regulators can be brought around to recognize that stringent controls on pollution from refining tar sands crude are imperative.  We can hold out hope that IDEM’s more cooperative tone reflects the shape of things to come.”

Follow WBEZ NWI bureau reporter Michael Puente on Twitter @MikePuenteNews and on Facebook.