Enbridge has to clean up water it polluted decades ago in order to use it for Line 3 dewatering

Enbridge’s controversial plans to increase dewatering during Line 3 construction got an added complication: Workers need to dewater in areas where the company had past crude oil spills, leaving 8,400 gallons in ground for decades.

That means Enbridge has to treat the dewatered polluted water before returning it to the environment.

A few questions immediately come to mind:

  • Enbridge and state regulators knew, or should have known, about these polluted sites. Why is this information only now coming to the public’s attention on the dewatering work?
  • If Enbridge is able to clean up this old crude oil spill to build its new Line 3, why wasn’t it required to clean it up a long time ago?

Information on these old spills was something of an afterthought, appearing in Enbridge’s Aug. 12 compliance filing with the Minnesota Public Utilities Commission (PUC).

To recap, Enbridge Line 3’s proposed route crosses a lot of wet areas, including wetlands and streams. When workers dig a trench it can fill with water, making work difficult. The company initially applied to the Minnesota Department of Natural Resources (DNR) to dewater 510 million gallons of water so workers could dry out the trench and install the pipeline.

During a drought year, one would think Enbridge would have needed less dewatering, not more. Instead, Enbridge applied to the DNR this year to increase its dewatering to 5 billion gallons, nearly a ten-fold increase. (Enbridge proposed a more water-intense dewatering process. Instead of using sump pumps to dry out the trench, Enbridge proposed drilling pipes below trench level, pumping groundwater out to depress the local water table, and dry out the trench.)

The DNR approved the dewatering increase over the opposition from the White Earth Nation, which worried about the dewatering’s impact on wild rice.

Now Enbridge is reporting that two of the dewatering sites in Carlton County are near old crude oil spills. (They are on both sides of I-35, south of Highway 210, see map below.)

Dewatering sites that overlap with past crude oil spills. Source: PUC filing.

The Minnesota Pollution Control Agency (MPCA) agreed to modify Enbridge’s discharge permit, describing the change as correcting “a small language omission.”

According to its filing, Enbridge plans to dewater near Leak Sites 83 and 84, both what it called closed crude oil leaks. Site 83 was remediated in 1972, and Site 84 in 1955.

Past cleanup efforts accounted for all but an estimated 100 barrels of crude oil at each of the two sites, Enbridge’s compliance filing said. (At 42 gallons per barrel, that’s a total of 8,400 gallons at the two sites.)

Enbridge’s plan is to treat the contaminated water pumped out of Site 83 and discharge it onto land as much as possible. If doesn’t adequately filter into the soil, workers will discharge the treated water into a coniferous swamp wetland, which flows into an unnamed Little Otter Creek tributary.

Workers will try to discharge the treated contaminated water from Site 84 onto land, too. If it doesn’t adequately filter into the soil, workers will discharge it into an “alder thicket wetland … with overland flow to Little Otter Creek.”

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