The Pipeline and Hazardous Materials Safety Administration, the U.S. Department of Transportation's regulatory arm, said it had summoned Enbridge Inc. executives in February to discuss problems with the 1,900-mile Lakehead system. Enbridge owns the pipeline that burst, sending oil into Talmadge Creek, which flows into the Kalamazoo River.
The pipeline safety agency informed Enbridge in January that it might have violated safety codes by improperly monitoring corrosion in the pipeline.
The Environmental Protection Agency estimates more than 1 million gallons of crude escaped, while the Canadian company puts the total at 820,000 gallons.
"Safety is our No. 1 priority," Bizunesh Scott, chief counsel for the federal agency, said in a written statement. "That's why we repeatedly pushed Enbridge to address the safety and performance of its entire Lakehead Pipeline system."
The agency has cited Enbridge or its affiliates for 30 enforcement actions since 2002.
Enbridge spokeswoman Gina Jordan said company officials have regular meetings with the agency to discuss operations and inspection results, including the one earlier this year.
"As the largest oil pipeline system in the world with close to 15,000 miles of liquids pipelines in the U.S. and Canada, Enbridge works closely with PHMSA and all our regulators to ensure we not only meet, but exceed safety requirements," Jordan said.
Also Saturday, EPA said it had rejected the company's long-range cleanup plan because of "deficiencies in content and technical details." It ordered Enbridge to submit a revised version by Monday.
In a letter to the company, the EPA said the pipeline repair section lacked a sufficient description and schedule of work to be done. It said water and sampling analysis would have to deal with odor complaints in the Marshall area the night of July 25, although Enbridge says it didn't confirm the spill was happening until the next day.
The EPA also said wetlands, floodplain and marshes should be included in the list of downstream areas to be cleaned.
Enbridge CEO Patrick D. Daniel said the company will modify the plan to meet EPA requirements. He also said the company has submitted a separate short-term cleanup blueprint that the EPA is reviewing.
Meanwhile, company and government officials said they had located the pipeline fissure that caused the spill. Once removed, the section was expected to be taken to a National Transportation Safety Board lab for testing.
U.S. Rep. Mark Schauer said the House Transportation and Infrastructure Committee had begun investigating the spill.
"Enbridge needs to answer some tough questions about how this happened," the Michigan Democrat said.
According to a timeline released Saturday by the Pipeline and Hazardous Materials Safety Administration, Enbridge last year discovered 250 imperfections with the line that eventually would rupture. The company immediately fixed 35 of them but is still working on the others.
During a March meeting, Enbridge gave the agency an updated plan for dealing with the problems. But the company requested permission this month to continue operating the pipe at lower pressure - which reduces the speed and volume of oil - for 2 1/2 years to allow more time for repairs.
After an April drilling rig explosion triggered the Gulf of Mexico spill, the federal agency ordered pipeline companies to review their spill response plans. Enbridge reported July 21 that it had conducted a "thorough review and update" and concluded it was "appropriate for responding to a worst case discharge," according to the agency's timeline.
The agency said it would review Enbridge's response to the Michigan spill "in light of these representations."
Daniel and other executives have defended the company's safety record for the Lakehead network, which transports oil between Neche, N.D., and Marysville, Mich.
The Calgary, Alberta-based company shut down the pipeline Monday and had been looking for the break since. Crews had a difficult time reaching the damaged section because it's in a marshy, oil-covered area.
"It is highly unlikely there is any other break in the pipe" other than the one that was exposed, said Steve Wuori, an Enbridge executive vice president.
Wuori said no oil was leaking from the pipe.
Enbridge has declared the spill contained and says it is focusing solely on cleanup. The company said Saturday it was increasing the size of its team and the equipment at the site and that it has recovered more than 1.2 million gallons of combined water and oil. The mixture contained about 210,000 gallons of crude, the company said.
Daniel also said the company had begun processing claims from people directly affected by the spill. The cause of the spill remains undetermined, he said.
"We will make good on any damage caused by the incident," he said at a news briefing.
Flesher reported from Traverse City, Mich.