Cleanup crews are finding more oil-fouled sections along the Yellowstone River as floodwaters recede after an Exxon Mobil Corp. pipeline failure, but officials said Monday that the extent of pollution did not appear to be growing.
A total of 45 locations with oil had been found along the scenic waterway, an increase of 15 sites since Saturday, said Steve Merritt of the U.S. Environmental Protection Agency.
The number is likely to increase again as crews in boats and on foot reach areas previously inaccessible because of high water.
Most damage remained between the spill site and 25 miles downstream, with scattered areas of pollution all the way out to Pompeys Pillar National Monument, about 45 miles downstream, Merritt said.
No significant contamination has been found beyond an isolated spot 70 miles downstream of the July 1 pipeline spill near Laurel.
"The number of sites is going to increase dramatically as we get access to the river," Merritt said. "But it's not getting bigger. Dissipation (of oil) over the length of the river has reduced impacts as you get farther and farther from the spill site."
Exxon Mobil estimates up to 1,000 barrels of crude coming from Wyoming spilled into the river when the 12-inch Silvertip Pipeline failed for still-unknown reasons beneath the Yellowstone.
Because much of the oil was swept away by the river, only between 1 and 5 percent of the crude is expected to be recovered, EPA officials said Monday.
At a Monday briefing, Merritt presented photographs showing progress made at several cleanup sites that crews have been able to reach. For those, Merritt said, work is moving from the recovery of oil to the cleaning or removal of vegetation covered in crude.
Of the fouled sites, cleanup crews were working 18 on Monday.
"We've said from the outset that we are going to clean this up and stay until the job is done," Exxon Mobil spokeswoman Cynthia Bergman said.
More than 100 claims have been submitted to Exxon Mobil from individuals claiming property damage, agricultural losses and health problems, Bergman said. The "vast majority" were property claims, she added. A more specific breakdown was not available.
Despite reports of some people sickened by the fumes coming off the crude, officials said that air and water monitoring to-date has suggested no long-term health concerns.
The EPA planned to test drinking water from several hundred residential wells downstream of the spill as a precaution and take soil samples from oiled cropland.
A plan submitted by Exxon Mobil detailing its cleanup will have to be revised after the EPA said the company provided insufficient information on oil recovery and containment and remediation for slicked areas downstream and around the spill site.
Bergman said the company appreciated the EPA's feedback and would incorporate it into the plan.
A revised plan is due by July 17, said Montana Department of Environmental Quality deputy director Tom Livers.
"So far, we haven't seen any effort to take shortcuts," Livers said. "The proof will be when we're really done with the work plan and can make sure the state's cleanup standards are in there."
Meanwhile, a five-person team of oil spill experts from California began arriving in Montana to assist. Livers said the team would provide an independent source of expertise.
The failed pipeline provided about 40,000 barrels of oil a day to an Exxon Mobil refinery in Billings. There was no word on when it might be repaired.
As the company tries to find an alternative supply source, U.S. Sen. Max Baucus asked Exxon Mobil to pledge that it would not lay off any workers because of the spill.
Baucus said the company was considering deliveries by truck and through the Glacier Pipeline, which is operated by Conoco Phillips Pipeline.
Bergman declined to comment on what options the company has but said the refinery expects to meet its motor fuels contracts "for the foreseeable future." No layoffs are planned, she said.