The most toxic compounds in the estimated 50,000 gallons of oil that spilled into the Yellowstone River evaporated quickly after the pipeline break last month, leaving gobs of sticky crude that pose no threat to human health, federal officials said Thursday.
There were no surprises in the recently released results of air, water and soil samples taken after the July 1 pipeline break near Laurel, said Steve Merritt, the on-scene cleanup coordinator for the Environmental Protection Agency.
Samples taken downriver four days after the break showed that the most dangerous components like benzene, toluene and total xylenes were no longer in the oil. They likely evaporated, were broken down by ultraviolet light or dissolved into the water to be released at lower levels downstream, the EPA said.
The ugly, sticky goo that was left is made up of components that aren't a threat to human health and will continue to degrade, Merritt said.
"Those do not pose a toxicity threat," he said.
Montana Gov. Brian Schweitzer on Thursday announced similar findings from the state Department of Environmental Quality, which analyzed samples gathered by state workers and private citizens who took the governor up on his offer to do their own testing.
The 87 soil samples taken at 23 properties found low concentrations of petroleum at seven of the properties and another seven more with higher concentrations that required cleaning. As with the EPA samples, state officials found that the lighter, more toxic compounds had largely evaporated or weathered away.
Tests of groundwater and wells showed no significant contamination, Schweitzer said.
"We dodged a bullet," he said.
The state and federal announcements appeared aimed at alleviating concerns about the risk to public health from the oil that spread into the wetlands while the river was running high from snowmelt. As the water receded, cleanup officials found the spill contaminated roughly 60 percent of shoreline areas up to 30 miles downstream.
In the days following the spill, some residents along the river complained that the fumes caused them to become nauseous, dizzy and short of breath. They worried the oil could seep into their drinking water and harm their crops and livestock.
One resident affected by the spill, Jim Swanson, said he's not convinced by the state and federal announcements. He is awaiting the results from his own soil and water samples taken by an expert hired by his attorney.
"I'm not disputing what they have come out with, but I would like confirm it before I form any kind of opinion," Swanson said. "You could actually see (the oil) burn itself off, and it's not a pretty sight. The thing is, it's in my tall grass and it's down there heavy."
Swanson said nobody has come to clean up his property, and he wants to see for himself whether the remaining oil poses any danger.
"I'd be grateful if there's nothing really wrong with it, but the fact remains that they dumped it on my property," he said, referring to pipeline owner Exxon Mobil. "I'm still exposed to it."
Merritt said landowners must go through a claims process to bring cleanup crews hired by Exxon to their properties.
"I think Exxon is going to do whatever a property owner requests of them," he said.
Air samples taken from several locations along the Yellowstone showed no public health concerns from the release of oil into the river. Explaining residents' sickness from the fumes, the EPA said hydrogen sulfide gas from the crude may have been an irritant "but was not detected by first responders at harmful levels in the ambient air."
Surface water samples taken between Laurel and Miles City showed no petroleum hydrocarbons above drinking water standards, while samples from dozens of private residences along the river verified that private wells were not affected by the spill, the EPA said.
More than 800 cleanup workers and support personnel are involved in cleaning the Yellowstone spill, with the cleanup expected to last into September, state officials have said.
State and federal officials said testing will continue in an effort to ensure that the job is being done adequately.
Associated Press writer Matt Gouras contributed to this report.