TIOGA, N.D. – Cleaning up the more than 20,000 barrels of oil that leaked from a pipeline near here will take at least $11 million and up to two more years, but a health official says the process should allow the land to be farmed again.
The North Dakota Department of Health announced Friday it has approved a remediation plan for the Tesoro Logistics pipeline spill that will involve excavating the contaminated soil and heating it to high temperatures to remove the oil.
The plan includes installing a segment of natural gas pipeline to the site to power the heavy equipment.
“It’s going to be a big operation,” said David Glatt, chief of the environmental health section.
An estimated 20,600 barrels – or 865,200 gallons – of oil spilled as a result of a pipeline leak discovered last September in a wheat field near Tioga. It’s the largest spill in North Dakota’s current oil boom and one of the largest onshore spills in recent U.S. history.
To date, about 6,000 barrels of oil have been recovered, Glatt said. Winter weather slowed recovery efforts.
“There really wasn’t much they could do when all the soil was frozen,” Glatt said.
Contractor Nelson Environmental Services will begin working at the site within the next few weeks with remediation expected to begin late this spring or early this summer, a Tesoro Logistics spokeswoman said.
The health department said remediation is expected to continue for at least two years. Tesoro says work is expected to continue into 2015.
Antea Group, a St. Paul-based environmental consultant firm, analyzed different technologies to clean up the soil and was in communication with health officials and the landowners, Steven and Patty Jensen.
The consultant recommended excavation and thermal treatment of the soil, estimating the cost at $11 million to $15 million in a report submitted to the health department. The Tesoro spokeswoman declined to comment on the cost, but said the company would pay for the full cost of remediation.
Glatt said the contaminated soil will be excavated and treated with equipment known as a thermal desorption unit. That piece of equipment requires a considerable amount of power, and the plan includes installing a natural gas pipeline to the site, Glatt said.
The natural gas pipeline is less than one mile long, the Tesoro spokeswoman said. Crude oil in the soil will act as a fuel source and natural gas will be a supplemental fuel source, she said.
After the soil is treated, it is tested, stockpiled and returned to the excavation.
“We’re thinking it’s all going to be treated on site and put back on site,” Glatt said.
The area that is contaminated is about 2.5 acres within a 7-acre site. Some contamination extends 30 feet below ground, with contamination as deep as 42 feet below ground in four small pockets, the consultant’s report said.
Monitoring wells and tests of private water wells in the area have not shown any impacts to groundwater, the consultant’s report said.
Recently, Tesoro officials notified the health department the contamination may have spread a little bit, Glatt said. The health department has asked the company to define the boundary of the contamination.
Health officials will oversee the cleanup, likely visiting the site weekly during the early stages, Glatt said.
The thermal treatment technology has been successfully implemented at sites with similar crude oil impacts and is capable of reducing crude oil concentrations to very low levels, the consultant’s report said.
Some cons to the method include potential for noise, nuisance odor and dust generation, the need to import suitable topsoil to the site and the significant power requirements, the report said.
Other methods investigated would have been less effective, taken more time, involved significantly more truck traffic, or affected a larger footprint, according to information submitted to the health department.
Glatt said the method selected aims to restore the land to its original state.
“We want it to be as productive post-pipeline break and remediation as it was pre-pipeline break,” Glatt said.