KALAMAZOO (AP) – The U.S. Environmental Protection Agency on Thursday ordered Enbridge Inc. to dredge sections of the Kalamazoo River to remove sediments tainted by oil from a massive spill.

More than 800,000 gallons spewed into the river and a tributary creek in July 2010 after the rupture of an underground pipeline near Marshall in southwestern Michigan. Oil flowed about 35 miles before it was contained. An investigation by the National Transportation Safety Board determined that the rupture was caused by cracks and corrosion, and the agency faulted Enbridge for failing to take steps that might have prevented it.

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The EPA said Thursday it had confirmed the presence of submerged oil in three areas and determined it could be removed through dredging.

“The dredging activity required by EPA’s order will prevent submerged oil from migrating to downstream areas where it will be more difficult or impossible to recover,” the agency’s regional office in Chicago said in a statement. In a letter to the company, it said the dredging is needed to protect public health and the environment.

The Canadian company has five days to respond to the order and 15 days to provide a work plan. The dredging should begin this spring and isn’t expected to require closing any of the river, the EPA said.

Enbridge, based in Calgary, Alberta, said it would “study the order in detail and respond accordingly.”

The targeted areas are above Ceresco Dam, upstream from Battle Creek and in the Morrow Lake Delta. The agency also told Enbridge to keep sediment traps in the river to capture oil where no dredging is required.

“We are, as we have always been, focused on cooperation with the EPA and other authorities in doing what is best for the river and the environment based on analysis and sound science,” spokesman Jason Manshum said.

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The company acknowledged some oil remains in the river but said it is weathered, degraded and “in extremely small concentrations.” It said the Michigan Department of Community Health had found that incidental contact with the oil would not pose a hazard and that water from private wells near the river was safe to drink.

The EPA initially proposed the additional cleanup work last October and issued the final order Thursday after taking comments from the company and the public.

The agency said it used a method called “poling” to locate the submerged oil. It involves stirring up soft sediments using a pole with an attached disc, causing oil to rise to the surface.

Enbridge response to EPA’s October proposal questioned the accuracy of data from poling and contended there was no immediate need for containment or recovery actions.

The 286-mile-long pipeline extends from Griffith, Ind., to Sarnia, Ontario. Enbridge is replacing and enlarging the line, part of a $2.6 billion project to boost the flow of oil to refineries in the eastern U.S. and Canada.

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