Portland Mayor Ted Wheeler says he’s exploring his options to try to block the growth of a terminal that unloads oil train cars in North Portland.

Zenith Energy, tucked between the river and Forest Park in the city’s northwest industrial district, began receiving train shipments of crude from Canada’s oil sands last year, records show. Now there are obvious signs of construction underway; the company is building three new rail platforms used to offload oil.

The expansion could more than double the number of oil trains that pass through Portland. The company received permits and approval for the project in 2014, but since then public awareness and opposition to oil train shipments has grown.

“I’m having legal counsel take a look at what options are available to me as mayor,” Wheeler said at his monthly press conference Tuesday. “I also have external partners who are interested in this question from an environmental perspective.”

Wheeler refused to be more specific, but suggested he is working with the same coalition of environmental groups that successfully lobbied for Portland’s moratorium on new fossil fuel infrastructure in 2016.