MDU Resources Group, Inc. (NYSE: MDU) and Calumet Specialty Products Partners, L.P. (NASDAQ: CLMT) announced that the North Dakota Department of Health has issued an Air Quality Permit to Construct for Dakota Prairie Refining, a diesel refinery the two companies are developing in southwestern North Dakota.

Approval of the air quality permit means that we can begin construction within the next month, and the facility can be operational and helping supply North Dakota's diesel fuel market by late 2014," said David L. Goodin, president and CEO of MDU Resources. "We are committed to operating this state-of-the-art facility responsibly and safely, and we appreciate the rigorous permitting process conducted by the health department."

"This facility will be an important contributor to the local and state economy," said Jennifer G. Straumins, president and chief operating officer of Calumet's general partner. "We appreciate the help of the state's agencies and officials to identify issues and help solve problems in a manner that has brought this project from concept to reality."

The facility will process 20,000 barrels per day of Bakken crude oil. The plant will be located on a 318-acre site located west of Dickinson in Stark County, N.D. It will employ approximately 100 people. Hiring and training of operating personnel is expected to begin in 2013. The plant will employ its own plant manager and management team, who will report to a governing board composed of representatives of WBI Energy and Calumet.