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. MDU Resources Group, Inc., a member of the S&P MidCap 400 index, provides value-added natural resource products and related services that are essential to energy and transportation infrastructure, including regulated utilities and pipelines, exploration and production, and construction materials and services companies. For more information about MDU Resources, see the company's website at www.mdu.com or contact the Investor Relations Department at firstname.lastname@example.org . Calumet Specialty Products Partners, L.P. is a master limited partnership and is a leading independent producer of high-quality, specialty hydrocarbon products in North America. Calumet Specialty Products Partners, L.P. processes crude oil and other feedstocks into customized lubricating oils, solvents and waxes used in consumer, industrial and automotive products. Calumet also produces fuel products including gasoline, diesel and jet fuel. Calumet Specialty Products Partners, L.P. is based in Indianapolis, Indiana and has eleven facilities located in northwest Louisiana, northwest Wisconsin, western Pennsylvania, Texas and eastern Missouri. Forward-Looking Statements Except for the historical information contained herein, the matters discussed in this release are forward-looking statements that involve certain risks and uncertainties that could cause actual results to differ materially from results anticipated in the forward-looking statements. These risks and uncertainties include, among other things, the ability of the parties to complete financing of the project, the ability of the parties to obtain required regulatory permits, the cost and time to complete the project, and the availability of crude petroleum product and markets for processed products. These and any other statements about future expectations, beliefs, goals, plans or prospects constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Any statements that are not statements of historical fact (including statements containing the words “believes,” “plans,” “anticipates,” “expects,” “estimates” and similar expressions) should also be considered to be forward-looking statements.