Enbridge Line 3 drilling fluid spills: What we know so far

By: - August 16, 2021 6:00 am

An Enbridge sign in St. Ignace, Michigan. The company is building the Line 3 pipeline in Minnesota. Photo by Susan J. Demas/Michigan Advance.

Enbridge is done drilling under rivers to build its Line 3 oil pipeline, but scrutiny over potential permit violations in the process isn’t likely to fade away anytime soon.

Enbridge spilled drilling fluid 28 times at 12 river crossings this summer, the Minnesota Pollution Control Agency announced last week. The news alarmed pipeline opponents — including some lawmakers — who had been demanding information about possible “frac-outs” along the route for weeks.

The MPCA released the information partly as a response to a group of 32 DFL lawmakers, who wrote the agency a letter in late July asking for information about the releases and urging the suspension of a key project permit until investigations were completed. 

Because the MPCA is investigating the spills, details about the incidents are classified as private under state law. The agency decided to release summaries to “dispel persistent misinformation circulating on social media,” an MPCA spokesperson told the Reformer.

Sen. Mary Kunesh, DFL-New Brighton, was one of the lawmakers who signed the letter. She said she felt the update validated their concerns — and left her with more questions.

“It just really, really concerns me,” Kunesh said. “We’d been assured and reassured this (drilling process) was safe. We’ll just have to keep a closer watch.” 

Here’s what we know so far about the drilling fluid spills and what to watch for in the coming months.

What is drilling fluid?

Drilling fluid is a mix of mud and chemicals used as lubrication for drilling under rivers.

In Line 3 construction, Enbridge is using bentonite clay — a fine, absorbent powder common in drilling fluid — with additives in some cases. The additives involved in reported spills include:

Where have the Line 3 spills happened, and how big were they?

Of the 28 spills, one was in a river, 13 were in wetlands and 14 were on land, according to the MPCA. They happened between June 8 and Aug. 5.

The amount of drilling fluid spilled ranged from 10 gallons to up to 9,000 gallons. Seven involved at least 100 gallons. The largest was a release of 6,000-9,000 gallons in a wetland near the Mississippi River.

To put that in context, a kiddie pool that measures 5 feet across and 2 feet deep contains about 230 gallons of water. So the largest release was between 26 and 40 kiddie pools. 

Pipeline opponents raised the alarm on social media about the spill in the Willow River in early July, sparking widespread concerns about other potential spills and timelines for cleanup.

According to MPCA records, Enbridge had started containment and cleanup efforts before activists arrived. The spill had “no impacts to any aquifers nor were there downstream impacts because environmental control measures were installed at the location,” Enbridge spokesperson Juli Kellner wrote in an email to the Reformer.

How do these spills happen?

To understand drilling fluid spills, you have to know a bit about horizontal directional drilling (HDD).

Pipelines are typically built by digging deep trenches, but that’s not a good option at rivers, busy roads or railroad tracks, for example. HDD is regarded as the least destructive method for laying pipes through these areas. 

In HDD, drilling fluid is pushed through the head of the drill bit as it creates a hole underground. The mix of bentonite clay, water and chemicals cools and lubricates the bit as it flows back toward the entry point, carrying drilling debris with it.

Spills are “not uncommon” near the drill entry and exit points on land, according to the MPCA. They also happen when the drill path crosses existing fractures in the ground, allowing fluid to flow to the surface.

The MPCA required soil structure analyses at each proposed HDD crossing to check for potential issues before approval. Still, “the risk of inadvertent release was not, and has never been represented as, zero,” MPCA Commissioner Peter Tester wrote in a letter to legislators in August.

Are the spills harmful to the environment?

That depends. The amount of fluid released, length of cleanup and water conditions can all influence how much spills affect the environment. A 10-gallon spill in a fast-moving river likely wouldn’t have much of an impact, but massive spills in other parts of the country — far larger than those reported in Minnesota — have polluted wetlands and contaminated drinking water.

Enbridge says drilling mud is nontoxic, and drilling operations are immediately shut down when spills are identified. Crews follow the containment and cleanup procedures outlined in project permits, and trained inspectors and third-party monitors supervise the process, the company says.

Laura Triplett, a geology and environmental studies professor at Gustavus Adolphus College, said she’s still concerned about potential affects on the river and wetland ecosystems because fine-grained bentonite can affect aquatic life; for example, by clogging the gills of freshwater mussels. Bentonite mud can also suffocate fish and insects, experts say.

Triplett said spills could contribute to the long-term degradation of wetlands, especially given the stress of the ongoing drought. Many people think of wetlands as “swamps, or a bunch of cattails, just something that’s not important,” she said. However, they perform vital roles like regulating river levels and filtering pollutants — as evidenced by the poor water quality across much of southern Minnesota, caused in part by the loss of the majority of the region’s wetlands, according to the MPCA.

How are spills cleaned up?

In response to inquiries about containment and cleanup of reported spills, Enbridge referred the Reformer to plans outlined in permitting documents. 

For wetland spills, workers use lightweight barriers like straw bales, sand bags and fencing to contain drilling fluid, then remove it with shovels or pumps. If there’s not enough fluid to physically remove it without causing damage, “with approval from both Enbridge Environment and Construction Management, the drilling fluid may be diluted with clean water and/or the fluid will be allowed to dry and dissipate naturally,” according to permitting documents.

In rivers, workers contain the fluid with sandbags, turbidity curtains and plastic sheeting, depending on water conditions, then remove it with pumps. 

Within 30 days of completing work at HDD crossings, Enbridge is required to submit a summary to the MPCA describing these efforts, if a spill took place. 

What happens next?

MPCA permits for the Line 3 replacement project bar Enbridge from releasing drilling fluid into wetlands or rivers, so 14 spills are under investigation as potential permit violations. The MPCA hopes to complete those investigations “later this fall,” according to an MPCA spokesperson.

In the meantime, construction on Line 3 is continuing. The pipeline is more than 80% complete and expected to carry oil by the end of the year.

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Rilyn Eischens
Rilyn Eischens

Rilyn Eischens is a former data reporter for the Minnesota Reformer. Rilyn was born and raised in Minnesota and has worked in newsrooms in the Twin Cities, Iowa, Texas and most recently Virginia, where she covered education for The Staunton News Leader. She's an alumna of the Dow Jones News Fund data journalism program and the Minnesota Daily. When Rilyn isn't in the newsroom, she likes to read, add to her plant collection and try new recipes.