The single-vehicle accident happened at the Balzac overpass near CrossIron Mills at about 4 a.m. MT, RCMP said.
The route is closed in both directions as hazardous materials response teams clean up the spill.
It's estimated 2,000 litres of fuel spilled into the ditch, while another 13,000 litres drained into the wetland, Rocky View County officials said.
Alberta Environment and Alberta Emergency Management Agency crews are on the scene to monitor the impact on the wetland.
The truck driver was not injured officials said.
The highway is expected to reopen later this morning.