At the gateway to the San Juan Islands sits the Andeavor (formerly Tesoro) oil refinery. It's a major employer in Anacortes, but also major air polluter.

The company now has a $400 million plan to upgrade and build new equipment to reduce emissions and produce cleaner fuels, but there's a catch.

"The problem is they've paired that with this Xylene manufacture and export project," said Alex Ramel with the environmental group Stand.earth.

Xylene is a toxic, flammable chemical used to make plastic. Some 630,000 gallons a day would be processed at the Anacortes refinery. A new pipeline would have to be built, and 60 additional tankers would navigate the waters each year bound for Asia.

Opponents say all that increases the risk for a catastrophic spill, endangering an already fragile ecosystem.

Ramel said that's not all.

"The greenhouse gasses from this project directly on this site are the equivalent of adding roughly 75,000 cars to the road."

However, local business leaders see the situation quite differently.

"It's a win-win," said Anacortes Chamber of Commerce President Stephanie Hamilton.

Hamilton believes the economic and environmental benefits of the upgrade outweigh any potential risks.

"The vapor emission control unit is going to be able to capture something like 98-percent of bad vapors. That's going to be good for everybody," she said.

The project would also create 20 new jobs -- jobs that would pay about $120,000 a year, according to Hamilton.

"For every job created at a refinery another job is created in the community," she said.

In order for the project to proceed, Skagit County must issue a special permit. Ramel believes it's a rare opportunity for the public to have a real impact on how the refinery is run.

Environmentalists see the permitting process as a way to further clamp down on pollution and enforce federal recommendations put on the refinery after a fatal explosion in 2010. Tesoro implemented some additional voluntary controls but has resisted others.

A decision from Skagit County is expected later this week.