As a black cloud of burning asphalt rose over Superior during the April 2018 oil refinery fire, nearly 100 tons of greenhouse gases rose with it.

To make up for those emissions, Husky Energy will install a solar array at the University of Wisconsin-Superior and help residents swap out old wood-burning appliances.

That’s the prescription outlined in a proposed settlement with the federal government and state of Wisconsin filed in federal court last week. The settlement is an amendment to one reached in a 2011 court case addressing violations of the Clean Air Act at the refinery.

A federal judge in Madison will decide whether to approve the settlement.

As part of the active $400 million rebuild of the fire-damaged refinery, the settlement also requires Husky to install additional safeguards around its hydrogen fluoride unit. The risk of a hydrogen fluoride (HF) release — though one did not happen — was the basis for the near-total evacuation of Superior as firefighters battled the April 26, 2018, fire.

The refinery is expected to reopen next year, and “rebuild costs are expected to be substantially covered by property damage insurance,” the company said in its earnings report Thursday.

Here are some of the key points outlined in the settlement:

Hydrogen fluoride

Residents and officials urged Husky to stop using hydrogen fluoride, a highly toxic chemical that can turn into a deadly gas cloud in a worst-case scenario, but the alternative wasn’t “commercially viable,” the Calgary, Alberta-based company said.

The settlement would require upgrades to equipment or operations “as an overall improvement to those currently in place.”

That includes advanced leak detection, a backup holding tank, video monitoring and more water mitigation measures, such as remotely operated water cannons.

Solar

If the settlement is approved as written, a solar array with a capacity of at least 440 kilowatts would be installed on the campus of the University of Wisconsin-Superior, which is several miles from the refinery.

The array would need to have at least a 25-year life span. It is expected to offset about 30 tons of greenhouse gas emissions.

Wood-burning stoves

Under the settlement, the refinery would be required to spend “at least $290,000” on rebates, vouchers, discounts or other methods of helping residents in northwestern Wisconsin replace or retrofit inefficient wood-burning appliances.

The project is expected to reduce over 280 tons of carbon monoxide, volatile organic compound and particulate matter.

What was released

According to the settlement, the explosion and fire at the refinery released:

• 31.6 tons of particulate matter

• 22.6 to 48.3 tons of volatile organic compounds

• 16.8 tons of sulfur dioxide

• 6.3 tons of carbon monoxide

• 0.2 tons of nitrogen oxides