BP’s Whiting Refinery is seen along the shore of Lake Michigan on Tuesday, March 25, 2014, in Whiting, Ind. BP says it is assessing how much crude oil entered Lake Michigan following a malfunction at its northwestern Indiana refinery. (AP Photo/The Times, Kyle Telechan)
Coast Guard spokesman Chief Petty Officer Alan Haraf said the estimate came from BP's initial visual assessment Tuesday of the spill scene at the company's Whiting refinery some 20 miles southeast of downtown Chicago.
One barrel of oil contains about 42 gallons, meaning the estimate indicates between about 378 and 756 gallons of crude oil were released into the lake.
Haraf said a more accurate figure likely will be released later this week on how much oil entered the lake, where crews for BP continued their cleanup work Wednesday. Those crews deployed absorbent booms following the spill, which affected a half-mile of private shoreline that's owned by BP and is not accessible to the general public.
The Environmental Protection Agency, which is supervising the cleanup work with the U.S. Coast Guard, said Tuesday that BP crews had used vacuum trucks to suck up about 5,200 gallons of an oil and water mixture from the site and had also removed oil globs from the shoreline.
The EPA issued a brief statement Wednesday saying an assessment team from the agency, the Coast Guard and BP surveyed the spill site Wednesday and found "minimal oiling of the shoreline."
The EPA said the survey team has recommended that crews continue to scour the shoreline to manually remove any remaining oil.
BP said in a statement Wednesday that its crews "have recovered the vast majority of oil that had been visible on the surface" of a cove-like area where the spill occurred.
The company said it continues its work to calculate how much oil was released into the lake during the spill, which was discovered Monday.
BP and EPA officials said Tuesday the spill apparently occurred when a malfunction allowed crude oil to enter a cooling system that draws lake water into the refinery to cool equipment and then returns that water to the lake.
Haraf said the spill area is confined to a cove area along the shoreline where BP discharges water from the refinery cooling operations into the lake.
The EPA has said the spill was not expected to pose any threat to municipal water supplies that draw on the lake's water.
Agency officials have said they are not aware of any previous oil spills at the site.
Dan Goldblatt, a spokesman for the Indiana Department of Environmental Management, said Wednesday a tentative review of recent state records also revealed no previous oil discharges into the lake from BP's Whiting complex.
Goldblatt said the state agency has no indication any oil had drifted beyond the immediate area along the lake where the spill occurred.
BP's Whiting refinery covers about 1,400 acres along the lake's shoreline.
The company completed work in late 2013 on a $4.2 billion expansion and upgrade of the refinery that will make it a top processor of heavy crude oil extracted from Canada's tar sand deposits.
That expansion sparked outrage in 2007 among environmentalists after they learned a state permit would have allowed BP to increase its discharges of ammonia and pollution called suspended solids into the lake.
BP announced in August 2007 that it would find ways to keep the expanded refinery's discharges to the limits set under its previous permits.