By ELIOT CAROOM
SAN ANTONIO (Bloomberg) -- A Tesoro line in North Dakota that carries oil from the Bakken shale formation to a rail operation leaked about 20,000 bbls of crude near Tioga, in the northern part of the state.
Tesoro shut the segment involved and repairs were under way, the company said in a statement. Most of the regions oil production, or about 67% in July, is exported by rail, with 25% sent by pipe and 7% used at Tesoros Mandan, North Dakota, refinery, according to the state Pipeline Authority.
The state was notified of the spill on September 30, and the initial estimate of the amount released was 750 bbls, said Dave Glatt, chief of environmental health for North Dakota. He said the extent of the 7.3 acre spill was discovered later because much of the oil is below the surface, permeating the soil to a layer of clay 10 to 12 ft underground.
The line carried domestic crude to a rail site at Battleview, Maxine Herr, a spokeswoman for the state Mineral Resources Department in Bismarck, said by phone.
The spill is the second-largest in state history, Glatt said. The date of the release wasnt known. Its probably something thats been going on for a little bit of a time, we just dont know how long, Glatt said. Due to the extent of what happened, what kind of leak was it and what kind of safeguards in place do they have to detect these things, that will be part of the investigation.