The clean-up by Tesoro Corp. of a nearly 21,000-bbl oil pipeline leak in North Dakota in 2013 will continue into next year, a state health department official said Wednesday.
"There is still active remediation ongoing at the site,” which is in the heart of the Bakken Shale about 10-12 miles northeast of Tioga, and Tesoro is “still in the process of cleaning it up," said North Dakota Department of Health’s Bill Suess, spill investigation program manager.
Suess said the company had projected completing the clean up this spring, but he expects the project to continue into the fall.
There will be several years of monitoring the site by the company and the state after everything is excavated, treated and backfilled, Suess said, noting that state officials need to assure there continues to be no impact on underground domestic water supplies.
Tesoro has spent nearly $50 million to date for a clean-up effort originally estimated at about $61 million, he said.
An eventual fine for Tesoro would be determined after the remediation work is completed. "It is a nice motivating factor, but in this case it wasn't needed," Suess said.
Three years ago, a 20,600 bbl spill from a leak in a Tesoro Logistics LP (TLLP) pipeline in a wheat field was not fully contained for several weeks, according to state and company officials. Originally detected in late September 2013, the leak was mistakenly thought to be smaller.
The incident has had widespread impact on both industry and state oil/gas stakeholders, and North Dakota redefined its policy for handling oil/natural gas releases as a result, culminating in a series of reports of small incidents in fall of 2013. Longer term, state officials set new guidelines affecting both the Department of Mineral Resources (DMR) Oil/Gas Division and the health department.
The state initially issued a notice of violation and the U.S. Department of Transportation's Pipeline and Hazardous Materials Safety Administration (PHMSA) issued a safety order to the Tesoro High Plains Pipeline in response to the leak, the largest in the nation in 2013.
Tesoro has addressed the remediation work as expected, Suess said, but the size of the spill has caused the cleanup to linger. What is involved is a 45-foot deep excavation spread over 13 acres and the related treatment of all the soil.
"This was a buried pipeline that leaked slowly over a long period of time, so most of the spill went down rather than coming up," Suess said. "There has been a lot of digging, so it is a slow process of digging and processing on site and then backfilling areas."
The 20-year-old six-inch diameter pipeline involved carries crude oil north of Tioga to Columbus, ND, where it is loaded on railcars for shipment to various refineries.
Despite the prolonged aftermath of the spill clean up, Tesoro has maintained a hearty appetite for investing in North Dakota. TLLP went on a buying spree in November, scooping up $700 million in assets in the state, and earlier in the year Tesoro acquired the Dakota Prairie Refinery in the Bakken from a unit of MDU Resources Group.