Frequently Asked Questions about the Superior Refinery incident


General Questions

1. What did burning asphalt release into the air? Is it harmful?

Based on air quality monitoring, the levels of emissions do not appear to have been harmful.

The refinery produces three different grades of asphalt, which generally have similar properties. Asphalt is a thick liquid refined from crude oil. Its most common use is to construct roads. It contains heavy petroleum compounds, sulfur, and trace metals such as iron, nickel, and vanadium.

The black smoke during the fire was caused by the asphalt burning and was a mixture of particulate and gases.

2. What else was released into the air during the fire? Is it harmful?

Based on air quality monitoring, the levels of emissions do not appear to have been harmful. In addition to asphalt, the refinery produces gasoline and diesel. When gasoline and diesel burn, they produce carbon dioxide and water vapor, similar to when fuel combusts in a vehicle.

3. What is in the foam used to put out the fire? Is it harmful?

Firefighting foam is very important, in part because it can remove oxygen from the fire and prevent the release of vapors. As with many chemicals, the foam is potentially harmful if ingested. The foam contains chemical components collectively known as Perfluoroalkyl Sulfonate (PFAS).

We are regularly collecting surface water samples from our on-site storm water ponds, and at multiple locations along the length of Newton Creek. Water samples collected from Newton Creek post-incident to date are comparable to baseline samples collected prior to the incident under normal refinery operating conditions, with the exception of trace amounts of PFAS.

Water from the site is treated at the refinery’s wastewater treatment plant and then moved through a treatment system designed to remove PFAS-related compounds, consisting of specialized granular activated carbon, followed by a polishing resin. It is then discharged, following normal refinery practice. The PFAS-treatment system was designed in close consultation with the Wisconsin Department of Natural Resources.


4. Was Hydrogen Fluoride released?

No. The first layer of protection in place, the fire suppression system, worked as it was designed to.

The tank was not compromised in the fire.

The HF storage tank is designed with multiple protection levels including a dedicated deluge system that douses the tank with a water curtain to keep it cooled and mitigate potential releases.

The HF tank also has a pressure safety valve. In the event pressure builds in the tank, the safety valve opens and the HF gases flow to a scrubber where they are neutralized and sent on to the flare system for destruction. The remaining liquid HF would be drained to the acid neutralization pit and rendered safe.

5. Who was doing the air and water monitoring after the incident?

Husky and the Wisconsin Department of Natural Resources tested water quality. Husky and the Environmental Protection Agency monitored air quality, with results posted on the Douglas CountyHealth and Human Services website.

6. Were there harmful substances inside my home?

Particles in smoke are not easily transported inside buildings. The gases that may have been produced by the fire dissipate naturally and would not remain inside a home.

7. I am concerned about my health, what should I do? What if I inhaled smoke during the incident?

Please contact your medical provider if you have any concerns about your health.

8. What about soot?

If you have questions with respect to soot, you should contact the Douglas County Department of Health and Human Services.

Read information from the Douglas County Department of Health and Human Services and the Wisconsin Department of Health here.

9. Do I need to clean inside my home or in my ducts?

It is unlikely that particles or gases made it into homes.

10. Is it safe to play outside?

Smoke from the fire was likely removed from play surfaces by natural processes, such as rain or snow, in the weeks following the incident.

11. What about soil and gardening?

Read information from the Douglas County Department of Health and Human Services and the Wisconsin Department of Health here.

12. Did you do any soil sampling? How do you know soil and livestock in areas affected by the smoke plume are safe?

The Wisconsin Department of Health Services says soil sampling would not have been useful due to the lack of visible soot deposition. Its memo posted to the Douglas County Department of Health and Human Services’ website states: “We do not have reason to believe soils or livestock in the areas downwind from the fire have been affected in any way that should alter gardening or farming practices or the use of agricultural products from those areas.” The memo can be found here.


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Husky Superior Refinery