AMHERST, S.D. -- Although studies are continuing, a preliminary report said a problem that started during construction of the Keystone pipeline almost 10 years ago may have led to the leak of 210,000 gallons of crude oil in a prairie grass field near the South Dakota-North Dakota border in November.
A report said the pipeline rupture may have been caused by a half-moon-shaped concrete weight placed on the 30-inch pipeline to hold it in place in the field near Amherst in northeast South Dakota where there was shallow groundwater.
The report from TransCanada and the federal Pipeline and Hazardous Materials Safety Administration “indicates the failure may have been caused by mechanical damage to the pipeline and coating associated with a weight installed on the pipeline in 2008.”
The report said weights or collars are placed on the pipeline in areas where shallow groundwater could potentially result in “buoyancy concerns.”
A portion of the pipe containing the location of the leak was removed last month and shipped to the National Transportation Safety Board's metallurgical lab in Virginia for further testing. No final report or cause has been released.
A leak in the same pipeline in southeast South Dakota in April 2016 where about 17,000 gallons of oil leaked was found to be caused by a bad weld.
Construction on the Keystone pipeline started in June 2008 and finished in March 2010, with the North Dakota and South Dakota portions among the first completed.
The pipeline running from Alberta in Canada through those two states and Nebraska, Kansas and Missouri to Patoka, Ill., was shut down this past fall on Nov. 6 after the leak was detected. Once found, the company said an emergency response was started within 15 minutes as the pipeline was shut down.
The pipeline from Illinois to the Texas coast refineries remained opened. The northern stretch of the pipeline started up again on Nov. 28, at first with reduced pressure.
Since the leak was found, cleanup of the site has been an ongoing project lead by TransCanada officials and environmental consultant Burns and McDonnell Engineering Co. of Kansas City, Mo.
It’s about half done, according to Brian Walsh, a scientist with the South Dakota Department of Environmental and Natural Resources ground water quality program, which receives and writes regular reports on the cleanup.
After first using vacuum trucks and absorbent pads to recover about 55,000 gallons of free crude oil from on top of the ground, a crew of more than 150 workers began excavating the contaminated soil on Dec. 6.
Reports examined by the Forum News Service state that the oil leaked was not the tar sands oil, but “conventional crude oil.”
Walsh said that before a holiday break was taken in the cleanup starting Dec. 22 and continuing through next Tuesday, Jan. 2, about 840 truckloads of contaminated soil had been hauled to the Clean Harbors landfill in Sawyer, N.D.
The landfill, about 220 miles away near Minot in north-central North Dakota, is for industrial waste, Walsh said. Because the soil is below more contaminated standards, it doesn’t have to be taken to other more restricted landfills.
“Cleanup has been moving along pretty well,” Walsh said. “It’ll be several more weeks, though, before it’s done.”
Reports set a date of Feb. 28 for completion of most of the cleanup project.
Other information in reports state that other damage from the oil leak appear to be fairly minimal. Checks of two private wells, with the nearest 2.5 miles away, found no contamination.
Water in a ditch about 275 feet from the spill also passed testing.
TransCanada continues to also monitor air quality and has 37 soil borings in the area with 24 samples sent to a lab for testing for certain chemicals.
An eagle’s nest about a mile from the spill is even being monitored in cooperation with the U.S. Fish and Wildlife Service.
After soil is removed, workers are backfilling dirt in clean areas. That step is already underway.