A saltwater spill estimated at 42,000 gallons flowed into a tributary of a Missouri River reservoir in western North Dakota, damaging vegetation in its path but not threatening drinking water sources, a state health official said.
Inspectors and cleanup crews have been on the well site since the spill earlier this week in McKenzie County, said Kris Roberts, an environmental geologist with the North Dakota Health Department. Houston-based Oasis Petroleum Inc. reported the spill Wednesday, Roberts said.
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Saltwater is an unwanted byproduct of oil production and can be many times saltier than sea water. It is considered an environmental hazard can easily kill vegetation exposed to it.
Roberts said the briny water spewed from a corroded steel pipeline near the well site. Some of the wastewater was cleaned up at the site but some of it reached a creek that is a tributary to Lake Sakakawea, about 5 miles downstream. The wastewater contained no chemicals used in drilling operations, he said, adding that the saltwater likely will be diluted to safe levels by the time it drains into the Missouri River reservoir.
"By the time it reaches Lake Sakakawea, I doubt if we'll even be able to detect it," Roberts said.
Oasis Petroleum did not immediately return calls on Friday. Roberts said the company is removing 6-inches of topsoil along damaged areas of the creek and replacing it with fresh dirt.
North Dakota, the nation's No. 2 oil producer behind Texas, also produces millions of barrels of briny wastewater daily.
The pipeline breech was the second saltwater leak in recent months to threaten Lake Sakakawea, the biggest reservoir on the Missouri River dam system.
About 1 million gallons of saltwater leaked from a pipeline in July near a tributary of Lake Sakakawea. The Environmental Protection Agency said it had no confirmed reports that the saltwater reached Bear Den Bay on Lake Sakakawea. The water body provides water for the Fort Berthold Indian Reservation in the heart of western North Dakota's booming oil patch.
The EPA said most of the spill was pooled on the ground, soaked into the soil and held behind beaver dams.
North Dakota had 74 pipeline leaks in 2013 that spilled 22,000 barrels of saltwater, 17,000 barrels of which was from a single spill in Bowman County, state records show. Oil drillers in the state produced a record 313.5 million barrels of crude in 2013 along with about 350 million barrels of contaminated water, state data show.