INDIANAPOLIS | A prominent Northwest Indiana Democrat plans to grill state officials over controversial decisions to allow major expansions of the BP oil refinery in Whiting and Horseshoe Casino in Hammond.

In a statement late Tuesday, state Rep. Scott Pelath, D-Michigan City, said he will use his position as chairman of a legislative study committee to conduct a "vigorous" investigation of state environmental regulators' recent decision allowing BP to dramatically increase water pollution.

"The Indiana Department of Environmental Management permitted a major manufacturer to discharge (more) ammonia and sludge into Lake Michigan," Pelath said. "I need to understand who made this decision, and why."

IDEM officials weren't available for comment late Tuesday. A new waste water discharge permit approved last month by state and federal regulators will allow the refinery to increase daily ammonia output 54 percent and release 35 percent more sludge as it moves ahead with a $3.8 billion plant expansion expected to create 80 jobs.

Pelath also wants answers about the $485 million Horseshoe Casino expansion that is expected to bring 450 jobs to Hammond.

Pelath, whose constituent base includes Blue Chip Casino in Michigan City, long has argued that the Indiana Gaming Commission might have overstepped its bounds in granting preliminary expansion approvals for Horseshoe and a southern Indiana casino. The commission since has finalized construction rules that Horseshoe officials say will force no changes in their construction plans.