BISMARCK, N.D. (AP) — North Dakota regulators are expected to take action Wednesday on a proposal to expand the capacity of the Dakota Access pipeline.

The Public Service Commission signaled last month that it would approve a permit for a pumping station that’s needed for Energy Transfer to double the capacity of the pipeline to meet growing demand for oil shipments from North Dakota.

Opponents say the expansion would increase the possibility of an oil spill. They argue the commission should have considered effects all along the line and not solely at the pump station location.

Permits for pumping stations in Iowa and Illinois are still pending.