BISMARCK, N.D. (AP) — Electronic monitoring equipment failed to detect a pipeline rupture that spewed more than 176,000 gallons of crude oil into a North Dakota creek, the pipeline's operator said Monday. 
 
 It's not yet clear why the monitoring equipment didn't detect the leak, Wendy Owen, a spokeswoman for Casper, Wyoming-based True Cos., which operates the Belle Fourche Pipeline, said. 
 
 A landowner discovered the spill near Belfield on Dec. 5, according to Bill Suess, an environmental scientist with the North Dakota Health Department. 
 
 Suess said the spill migrated about almost 6 miles from the spill site along Ash Coulee Creek, and it fouled an unknown amount of private and U.S. Forest Service land along the waterway. The creek feeds into the Little Missouri River, but Seuss said it appears no oil got that far and that no drinking water sources were threatened. The creek was free-flowing when the spill occurred but has since frozen over. 
 
 Suess said about 37,000 gallons of oil had been recovered as of Monday. 
 
 Owen said the pipeline was shut down immediately after the leak was discovered. The pipeline is buried on a hill near Ash Coulee creek, and the "hillside sloughed," which may have ruptured the line, she said. 
 
 "That is our No.1 theory but nothing is definitive" Owen said. "We have several working theories and the investigation is ongoing." 
 
 True Cos. has a history of oil field-related spills in North Dakota and Montana, including a January 2015 pipeline break into the Yellowstone River. The 32,000-gallon spill temporarily shut down water supplies in the downstream community of Glendive, Montana, after oil was detected in the city's water treatment system. 
 
 The 6-inch steel Belle Fourche Pipeline is mostly underground but was built above ground where it crosses Ash Coulee Creek, Suess said. 
 
 Owen said the pipeline was built in the 1980s and is used to gather oil from nearby oil wells to a collection point. 
 
 The company has hired Alberta, Canada-based SWAT Consulting Inc. that specializes in cold-weather oil spill cleanups, Suess said. 
 
 About 60 workers were on site Monday, and crews have been averaging about 100 yards daily in their cleanup efforts, he said. Some of the oil remains trapped beneath the frozen creek. 
 
 "It's going to take some time," Suess said of the cleanup. "Obviously there will be some component of the cleanup that will go toward spring." 
 
 True Cos. operates at least three pipeline companies with a combined 1,648 miles of line in Montana, North Dakota and Wyoming, according to information the companies submitted to federal regulators. Since 2006, the companies have reported 36 spills totaling 320,000 gallons of petroleum products, most of which was never recovered. 
 
 Federal pipeline safety regulators initiated 19 enforcement activities against the three True pipeline companies since 2004. Those resulted in $537,500 in proposed penalties, of which the company paid $397,200, according to Department of Transportation records. 
 
 The potential for a pipeline leak that might taint drinking water is at the core of the disputed four-state, $3.8 billion Dakota Access Pipeline, where thousands of people have been protesting its construction in southern North Dakota. That pipeline would cross the Missouri River. Dallas-based pipeline company Energy Transfer Partners says the Dakota Access pipeline would include safeguards such as leak detection equipment and that workers monitoring the pipeline remotely in Texas could close valves within three minutes if a breach is detected. 
 
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 Associated Press writer Matthew Brown in Billings, Montana, contributed to this report. ||||| FILE - This Oct. 11, 2013 file photo shows cleanup at the site of a Tesoro Corp. pipeline break that spilled more than 20,000 barrels of oil into a Tioga, N.D., wheat field. The massive oil spill still... (Associated Press) 
 
 FILE - This Oct. 11, 2013 file photo shows cleanup at the site of a Tesoro Corp. pipeline break that spilled more than 20,000 barrels of oil into a Tioga, N.D., wheat field. The massive oil spill still isn't fully cleaned up three years and three months after it happened. The company responsible hasn't... (Associated Press) 
 
 BISMARCK, N.D. (AP) — Three years and three months later, a massive oil spill in North Dakota still isn't fully cleaned up. The company responsible hasn't even set a date for completion. 
 
 Though crews have been working around the clock to deal with the Tesoro Corp. pipeline break, which happened in a wheat field in September 2013, less than a third of the 840,000 gallons that spilled has been recovered — or ever will be, North Dakota Health Department environmental scientist Bill Suess said. 
 
 A farmer, Steve Jenkins, who'd smelled the crude oil for days, discovered the spill in his northwestern North Dakota field near Tioga — his combines' tires were covered in it. 
 
 While the nearest home was a half-mile away and the state said no water sources were contaminated and no wildlife hurt, one of the largest onshore oil spills recorded in the U.S. serves for some as a cautionary example, especially given a recent pipeline break about 150 miles south and ongoing debates over the four-state Dakota Access pipeline. 
 
 "What happened to us happened and we can't go back," said Patty Jensen, Steve's wife. This month's pipeline break in Belfield, which belched an estimated 176,000 gallons of oil into a creek that feeds into the Little Missouri River, a tributary of the Missouri River, really rankled her. 
 
 "But I get really upset when I hear of a new one and I wonder what is being done to prevent these spills," she said. 
 
 Both the Tesoro break and the Belfield break occurred on 6-inch steel pipelines — a part of a large network pipelines that crisscross western North Dakota's oil patch. By comparison, the Dakota Access pipeline is made of 30-inch steel and will carry nearly 20 million gallons daily. 
 
 The Tesoro spill was not far from where oil was first discovered in North Dakota in 1951.The Texas-based company and federal regulators have said a lightning strike may have caused the 2013 rupture in the pipeline, which runs from Tioga to a rail facility outside of Columbus, near the Canadian border. 
 
 North Dakota regulators initially thought just 750 barrels of oil was involved in the spill, but later updated the amount exponentially. They also expanded the affected acreage from about 7 — the size of seven football fields — to about 13 acres, Suess said. The cleanup has cost Tesoro more than $49 million to date and is expected to top $60 million, according to recent filings to the state. 
 
 Tesoro spokeswoman Destin Singleton said she could not immediately confirm the numbers, and noted the cleanup completion date remains unknown. The pipeline was monitored remotely, but the company has said the spill wasn't detected. 
 
 Crews have had to dig as deep as 50 feet to remove hundreds of thousands of tons of oil-tainted soil, Suess said. The company has now switched to special equipment that cooks hydrocarbons from crude-soaked soil in a process called thermal desorption before putting it back in place. 
 
 The Dec. 5 spill on the Belle Fourche pipeline also was discovered by a landowner. Crude oil migrated about almost 6 miles from the spill site along Ash Coulee Creek, and fouled an unknown amount of private and U.S. Forest Service land along the waterway. Seuss said it appears no oil got as far as the Little Missouri River, and no drinking water sources were threatened. 
 
 It's not yet clear why monitoring equipment didn't detect the leak, according to Wendy Owen, a spokeswoman for Casper, Wyoming-based True Cos., which operates the pipeline. 
 
 The Dakota Access pipeline builder, Texas-based Energy Transfer Partners, has said the project will be safe and that workers remotely monitoring the pipeline will be able to shut it down if a leak is detected. 
 
 Owen said didn't know how long it would take to clean the Belle Fourche spill, given that wintry weather was slowing down the progress, or how much it would cost. 
 
 Patty Jensen is aware of the glacial pace of oil spill cleanups. For more than three years, it's been part the couple's life. 
 
 "They are there working away 24 hours a day, seven days a week — it's pretty amazing," she said. "The noise from the equipment used to bug us but we've grown used to it." ||||| BISMARCK, N.D. (AP) — A company with a history of oil field-related spills in North Dakota and Montana is being hampered by winter weather in its cleanup of a "significant" pipeline break that leaked crude oil into a tributary of the Little Missouri River in western North Dakota, a regulator said Thursday. 
 
 Bill Suess, an environmental scientist with the North Dakota Health Department, said the Belle Fourche Pipeline Co. spill was discovered Monday by a landowner near Belfield. The cause of the leak is under investigation and the amount of the spill is unknown, in part because of recent blizzards and subzero temperatures throughout North Dakota, he said. 
 
 "Anytime you have cold temperatures, it's going to hinder cleanup and the investigation," Suess said. 
 
 He said the spill migrated about 2½ miles from the spill site along Ash Coulee Creek, and it fouled an unknown amount of private and U.S. Forest Service land along the waterway. He said state and federal inspectors have been monitoring the spill and that it appeared to be contained. The creek was free-flowing when the spill occurred but has since frozen over. 
 
 The spill in the creek is about 20 miles upstream of the Little Missouri River. Suess said it did not appear that any of the oil reached the river and no drinking water sources were affected. 
 
 The 6-inch steel pipeline is mostly underground but was built above ground as it crossed the creek, Suess said. The pipeline is used to gather oil from nearby oil wells to a collection point. 
 
 "It is not a transmission line so overall it won't have a major impact on oil movement," Suess said. 
 
 Belle Fourche Pipeline is part of Casper, Wyoming-based True Cos. A spokeswoman for True, Wendy Owen, said the pipeline was shut down immediately after the leak was discovered and crews had been cleaning it up since. She said it was not known how much oil leaked due to the pipeline breach. 
 
 Owen said she "couldn't even begin to speculate" what caused the breach and that the company was doing its "best to assess the entire situation and what the next step will be." 
 
 True Cos. operates at least three pipeline companies with a combined 1,648 miles of line in Montana, North Dakota and Wyoming, according to information the companies submitted to federal regulators. 
 
 Since 2006 the companies have reported 36 spills totaling 320,000 gallons of petroleum products. Most of the product spilled was never recovered, including after a January 2015 pipeline break into the Yellowstone River. The 32,000-gallon spill temporarily shut down water supplies in the downstream community of Glendive, Montana, after oil was detected in the city's water treatment system. 
 
 The companies' spills caused combined damage of almost $11 million, with most of that attributed to the Glendive spill, records show. A federal investigation into that spill is pending. 
 
 Kevin Pranis, a spokesman for the Laborers District Council of Minnesota and North Dakota, which represents some workers building the disputed four-state, $3.8 billion Dakota Access Pipeline, said Thursday that regulators need to provide better oversight of the True Cos. 
 
 True Cos. also owns Black Hills Trucking Inc., which is accused of illegally dumping saltwater, a byproduct of oil production, in 2014 on a road in northwestern North Dakota. The three-member North Dakota Industrial Commission that includes Gov. Jack Dalrymple is pursuing $950,000 in fines against Black Hills Trucking, but there has been a dispute over whether the commission has jurisdiction. 
 
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 Associated Press writer Matthew Brown in Billings, Montana, contributed to this report.
– Three years and three months later, a massive oil spill in North Dakota still isn't fully cleaned up. The company responsible hasn't even set a date for completion. Though crews have been working around the clock to deal with the Tesoro Corp. pipeline break, which happened in a wheat field in September 2013, less than a third of the 840,000 gallons that spilled has been recovered. While the nearest home was a half-mile away and the state said no water sources were contaminated and no wildlife hurt, one of the largest onshore oil spills recorded in the US serves for some as a cautionary example, especially given a recent pipeline break in Belfield, about 150 miles south, and ongoing debates over the four-state Dakota Access pipeline. Texas-based company Tesoro and federal regulators have said a lightning strike may have caused the 2013 rupture in the pipeline, which runs from Tioga to a rail facility outside of Columbus, near the Canadian border. The cleanup has cost Tesoro more than $49 million to date and is expected to top $60 million, according to recent filings to the state. Crews have had to dig as deep as 50 feet to remove hundreds of thousands of tons of oil-tainted soil, North Dakota Health Department environmental scientist Bill Suess says. The company has now switched to special equipment that cooks hydrocarbons from crude-soaked soil in a process called thermal desorption before putting it back in place. Landowners, not the monitoring equipment in place, discovered both the Tesoro and Belfield breaks, reports the AP.