The Site is located in a mixed commercial/industrial area of Joliet, Illinois.   The most likely source of the oil spill is the Midwest Generation, Joliet Station, located at 1800 Channahon Road in Joliet, Illinois. The Midwest Generation, Joliet Station is located on the Des Plaines River. The geographic coordinates of Midwest Generation, Joliet Station discharge outfall are approximately 41°29' 36.61" North latitude and  88° 7' 23.32" West longitude. The Midwest Generation, Joliet Station discharge outfall is approximately 6.65 miles upstream from Interstate 55 (I-55) and approximately 1.5 miles upstream from the Hollywood Casino.  Adjacent to the Midwest Generation, Joliet Station to the east and downstream is the Caterpillar, Inc. Company. 

On Dec 6, 2012 at 4:23 pm the Caterpillar Inc. Company (Caterpillar) reported an oil sheen on the Des Plaines River adjacent to their property located at 2200 Channahon Road in Joliet IL (NRC 1032523). 

U.S. EPA OSC responded the morning of Dec.7 and observed an oil sheen plume upstream and downstream of Caterpillar on the Des Plaines River. The U.S. EPA OSC suspected that the oil sheen was accumulating at the Hollywood Casino (Casino), located at 777 Hollywood Blvd., about a 3/4 mile downstream of Caterpillar. A Casino representative reported the oil sheen to the NRC (# 1032602). After meeting with the Casino representative and inspecting oil sheen trapped at the Casino, the OSC determined that oil sheen was recoverable.  As a result, ERRS and START were activated and mobilized to the incident, arriving at about 5:30 pm.  Also, an account for $20,000 was opened under the Oil Spill Liability Trust Fund.

On Dec 7 at 6:30 pm the U.S. EPA OSC was diverted to the Midwest Generation, Joliet Station (Midwest Generation) located at 1800 Channahon Road, upstream of Caterpillar and the Casino.  Midwest Generation had reported an oil spill of 1,400 gallons (NRC #s 1032620 and 1032656). U.S. EPA and START met with representatives from Midwest Generation at the Midwest Generation, Joliet Station.  Midwest Generation representatives explained that a maximum of 1,400 gallons of mineral oil leaked from a 25-foot tall turbine oil cooler on the property.  The oil leaked into both the plant's cascading pond settling system and the plant's discharge outfall to the Des Plaines River.  Midwest Generation first observed sheen in Pond 3 of the plant's cascading pond settling system and in the plant's water intake channel off the Des Plaines River, where it was believed that sheen from the plant's discharge channel had recirculated upstream.  The turbine system from which the oil had leaked was taken off-line.  Midwest Generation informed U.S. EPA that SET was hired to perform cleanup activities on the Des Plaines River beginning the following morning, Dec. 8. 

The U.S. EPA OSC determined that Midwest Generation was the most likely source of the oil discharge into the Des Plaines River.   The U.S. EPA OSC issued Midwest Generation a Notice Violation under the Oil Pollution Act. Midwest Generation cooperated and ordered their cleanup contractor (SET) to mobilize additional resources. Midwest Generation provided EPA and START with a sample of the mineral oil from an on-site tank. In addition, the U.S. EPA OSC requested and received permission from Midwest Generation to collect surface water sample from Pond 3 of Midwest Generation's cascading pond settling system where sheen was observed at the water's edge. The sample was collected at about 8:15 pm and Midwest Generation collected a split sample

Since a potential responsible party was found, the U.S. EPA OSC ordered his cleanup contractor (ERRS) to stand down.  EPA's role then became oversight of the cleanup by Midwest Generation and its contractor.  Cleanup on the Des Plaines River. 

Based on its initial search, the U.S. EPA found no drinking water intakes within 11 miles downstream of the Midwest Generation Joliet Station.