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By Liz Hampton and Ernest Scheyder
HOUSTON, Dec 2 (Reuters) - Delays to the Dakota Access Pipeline have added millions of dollars to Energy Transfer Partners' construction tab - but even if the line is approved, the freezing temperatures will bring their own challenges to finishing the drilling process.
Frigid weather makes some aspects of pipeline construction more difficult, though not impossible, engineers and experts interviewed by Reuters said this week.
While the majority of the construction on the 1,100-mile (1,770 km) line is complete, work on a one-mile segment in North Dakota was halted in September following protests from the Standing Rock Sioux tribe and others, who said it could desecrate sacred lands and contaminate drinking water. That stretch would be expected to take 90 to 120 days to finish, ETP has said.
Construction equipment used to bore under rivers can break through any layer of frost, said Eric Hansen, the director of environmental services at Westwood Professional Services, a surveying and engineering firm in the U.S. upper Midwest.
At issue, however, is the fluid construction companies use to lubricate the drill head. That drilling fluid, which circulates to clear out debris and keep parts lubricated, freezes at air temperatures between 10 and 20 degrees Fahrenheit (-12 to -7 Celsius).
To avoid this, pipeline crews will keep equipment running nonstop, which allows them to avoid warming up equipment that's been turned off in cold weather, said an engineer who has done work in North Dakota but declined to be named.
The median temperature in Morton County, North Dakota, near the pipeline route is 13 degrees F between December and February, according to the National Weather Service. The NWS is forecasting a 60 percent chance that temperatures will be lower than that median for the next three months.
Hansen added that the high winds in North Dakota and heavy snow accumulation can also slow operations. The temperature in Cannon Ball, North Dakota was 30 degrees F on Thursday.
As the U.S. government weighs whether to grant Energy Transfer the easement, the pipeline operator said in a legal filing in late November that delays following the projected Jan. 1 start-up would cost about $84 million a month.
Energy Transfer Partners this week said it still expected to complete the pipeline in the first quarter of next year, even after the U.S. government in November further delayed a decision on whether to grant the company an easement needed to drill under Lake Oahe, a reservoir that is part of the Missouri River.