On Thursday afternoon, an oil spill into the St. Mary’s River at the Ontario, Canada-Michigan border halted boat traffic between Lake Superior and Lake Huron for about three hours. This spill is small, relative to the massive incidents that usually make the news. Spills of this scale rarely make headlines, and that’s a problem: Small events are the large majority of oil spills, and together they have a big impact.

5,300 gallons of oil originating from Algoma Steel fell into the river at around 10:30 am, according to a press release from the U.S. Coast Guard.

In response, Algoma Public Health—a local Canadian agency—warned residents who obtain their water directly from the St. Mary’s River not to drink it. The municipal water system was unaffected, but the direct advisory remains in effect as of publishing this story. The agency is also warning people to avoid swimming, bathing, or recreating in the river, and to keep pets away from the water.

The spill happened near the Soo Locks, which help move boats between the lakes. The locks were shuttered from noon to 3pm yesterday. No boats could pass, and a few commercial cargo ships were delayed.

The incident made a couple of national headlines, but wasn’t big news. There was a short Associated Press story about it that the Washington Post reprinted. For the most part though, the story stayed local.

Why? Spills like this happen all the time. The overwhelming majority of oil spills don’t show up in headlines at all. There are thousands of instances of oil leaking, oozing, pouring, and, yes, spilling into U.S. waters every year.

Unless it’s one of the most major spills, meaning one categorized as over 420,000 gallons by NOAA, or a large spill of over 219,000 gallons according to the International Tanker Owners Pollution Federation, most people never find out.

Sure, the St. Mary’s River spill is no Deepwater Horizon. But maybe all these small(er) spills should be big(er) news. It’s difficult to find reliable and comprehensive data on smaller spills. As far as Gizmodo can tell, there is no centralized tracker that shows volumes for all oil spill incidents that occur in the United States. But NOAA does keep tabs on a lot of spills via its incident tracker, which covers “selected oil spills off US coastal waters and other incidents.”

So far, in 2022 alone, NOAA has recorded more than 50 recorded oil incidents. Of that 50, the 45+ below both the ITOPF and NOAA thresholds have cumulatively spilled a potential 234,220 gallons of oil into our waterways.

Even small spills can still have big consequences. Water supplies can be impacted and shipping can be disrupted, as in the case of the St. Mary’s spill. And it doesn’t take 200,000 gallons of oil to cause environmental harm. Though different types of oil and different spills have varied effects, oil is poisonous to most living things. Plus, minor spills are often actually much bigger than reported, according to a 2014 study.

Both the Coast Guard and the Ontario Ministry of Environment (along with other environmental groups) are responding to yesterday’s spill in the Great Lakes. “We’re working in lock-step with our Canadian, American, and tribal partners to ensure the sanctity of our river,” local sector Coast Guard Commander, Anthony Jones, said in the CG statement.

In a phone conversation, a Coast Guard representative told Gizmodo that the military branch is still monitoring the St. Mary’s spill, but hasn’t yet deployed any clean-up equipment. A Coast Guard helicopter will be flying over the area on Friday to look for, and assess the expected oil sheen. The environmental impacts of the spill aren’t yet known, said the representative.

Algoma Steel issued the following statement to multiple news outlets:

A quantity of oil left our site early this morning and entered the adjacent waterway. The source of the spill has been safely contained.

The Ministry of Environment, Conservation and Parks, the Spills Action Centre, the Canadian Coast Guard and the City of Sault Ste. Marie have been notified and we are currently coordinating with officials, deploying equipment, resources and personnel to mitigate any possible impact to the environment.

The St. Mary’s River is 75 miles long and is the only connection between Lakes Huron and Superior. It’s been the site of industry like steel and paper production for decades, but remains one of the most biodiverse areas of the Great Lakes, according to the Michigan Natural Features Inventory. It encompasses marshes and other critical wetlands. The river is home to rare fish species like lake sturgeon and species threatened in the state like the yellow rail, a small bird.

To those critters, even “safely contained,” the oil spill might not seem so small.