Senators John Hoeven and Kevin Cramer and Representative Kelly Armstrong released a joint news release on Friday regarding Sandia National Laboratories’ study that found Bakken crude has comparable physical, chemical and combustion characteristics as crude from the Permian Basin and the Strategic Petroleum Reserve.

The Sandia study bolsters the delegation’s efforts to overturn a Washington State law requiring crude oil unloaded in the state to meet a 9 psi Reid Vapor Pressure, which would effectively block the Pacific Northwest as a destination for Bakken crude oil.

“The Sandia study proves that Bakken crude is not more volatile than other crude oil produced in the United States and can be safely and efficiently transported using the same standards as other oils,” said the delegation. “This study shows that the Washington State law has no basis for targeting Bakken crude.”

Wayne Stenehjem, attorney general for North Dakota, said Wednesday that the study “vastly undermines the reasoning behind the state of Washington enacting this statute because they assume without evidence that Bakken oil is more volatile,” according to an Associated Press story. “The net result is Bakken oil is no different than any other kind of oil with respect to volatility.”

The study analyzed oil from the Bakken, the Permian Basin in Texas and crude stored in the federal Strategic Petroleum Reserve, each with a different vapor pressure. Researchers conducted the studies by igniting pools of oil on fire and creating fireballs while measuring the height of flames, burn rate and fireball dimensions, among other factors, the Associated Press reported.

Kari Cutting, vice president of the North Dakota Petroleum Council, said in a statement that the study “conclusively determined” that Bakken crude does not have different physical and combustible characteristics from other crude oil, according to the Associated Press.

Earlier this month, Hoeven, Cramer and Armstrong led a bicameral letter urging Pipeline and Hazardous Materials Safety Administration to preempt the recently-passed Washington State crude-by-rail law. The letter supports the petition filed by the states of North Dakota and Montana, stressing that the Washington State law violates the U.S. Department of Transportation’s primary authority over the shipment of crude oil within the United States and the Interstate Commerce Clause of the U.S. Constitution.

Additionally, in June, the delegation contacted Transportation Secretary Elaine Chao to make the case that the Washington State crude-by-rail law violates the Interstate Commerce Clause of the U.S. Constitution and interferes with the U.S. Department of Transportation and its primary authority over the shipment of crude oil within the United States. The call followed a letter sent by the delegation to Washington Gov. Jay Inslee, outlining the law’s unscientific basis and lack of a solid legal foundation.

Current North Dakota regulations require companies to extract the most volatile gases from Bakken crude oil to guarantee the vapor pressure does not surpass 13.7 psi. North Dakota state officials established that threshold based on a national guideline for stable crude oil, which is 14.7 psi.

Rails transport more than 160,000 barrels of oil on a daily basis from North Dakota to refineries in Washington, which equates to roughly 11% of North Dakota’s day-to-day oil production.