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The contractor that damaged a natural gas pipeline in western North Dakota last week has a history of striking pipelines, including hitting 20 utility lines last summer during a project in Iowa.

Carstensen Contracting of Pipestone, Minn., was installing a water pipeline near Watford City last Thursday when it damaged a natural gas liquids pipeline owned by Oneok.

No one was hurt, but the damage caused the release of an estimated 3,000 barrels, or 126,000 gallons, of natural gas liquids.

It is at least the second natural gas pipeline the contractor has damaged in North Dakota while installing water pipelines for the Western Area Water Supply Project in the northwest part of the state.

In addition, city leaders in Fort Dodge, Iowa, “agreed to part ways” with Carstensen Contracting last summer after the contractor hit 20 underground utility lines in less than three months while working on a sewer project, said city engineer Tony Trotter.

The Fort Dodge Messenger reported Carstensen workers broke four gas lines, broke three water service lines, knocked down an overhead electrical line and cut a phone line. The company also left sandbags in a manhole, causing two sewage backups, the newspaper reported.

Trotter said Carstensen Contracting completed a successful project for Fort Dodge a year earlier.

The North Dakota Public Service Commission recently fined Carstensen $15,000 after investigating an alleged violation of the North Dakota One Call Law connected to damage of a different natural gas pipeline in 2015.

In that case, investigators determined that Carstensen called 811 four hours after damaging a natural gas pipeline in Williston, according to the PSC complaint. State law requires companies to call the hotline at least 48 hours before an excavation.

Oneok, which also owned that pipeline, alleged in a complaint that the incident caused $61,000 in damages and the loss of $294,000 worth of wellhead natural gas. In addition, a local homeowner had to evacuate for a day due to safety reasons, Oneok said in its complaint.

Carstensen reached a consent agreement with the PSC this spring, which included suspending $5,000 of the fine on the condition that the company commit no further violations within five years.

Public Service Commissioner Brian Kroshus said regulators have not received a complaint about last week’s pipeline strike, but the commission plans to investigate and could consider requiring the rest of the fine or filing a new complaint if the company is found at fault for the most recent incident.

“We will be taking a very close look at it,” Kroshus said.

Third-party damage to pipelines is by far the leading cause of pipeline spills, Kroshus said.

In last Thursday’s incident, Brad Carstensen, vice president for Carstensen Contracting, said the company took the necessary steps to locate underground oil and gas pipelines, including calling 811 and doing a hydro excavation to determine the depth of the pipelines.

The company is investigating why equipment struck the natural gas pipeline while crews were boring underneath two pipelines in McKenzie County. On the same project, Carstensen workers completed 25 other natural gas pipeline crossings in 7 miles without incident, the company’s vice president said.

“It’s a very, very dense area for underground pipelines, gas and oil pipelines,” Carstensen said.

The pipeline that was damaged serves Oneok’s Bear Creek natural gas processing plant. The pipeline is now repaired and back in service, but the damage caused the gas plant to be down for three days, Oneok said in a statement.

Carstensen said the company has since put a safety coordinator on the project full time, instead of a couple of days a week, and added a foreman with a lot of boring experience to manage the crew.

The Western Area Water Supply board selected Carstensen as the contractor because the company was the lowest bidder, said Mark Owan, chairman of the board.

“From our perspective, they’ve always done good work,” Owan said.

Few statistics are available about how often pipeline strikes occur in North Dakota. The PSC investigated 18 One Call complaints that related to pipelines last year, down from 31 in 2015 and 2014. But not all pipeline strikes lead to complaints.

The PSC is trying to get pipeline owners to voluntarily report how many line strikes occur each year, Kroshus said.

“The more information and data we have on hand, we can identify certain patterns that way and use it for educational purposes and awareness programs,” Kroshus said.

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(Reach Amy Dalrymple at 701-250-8267 or