Forklift was being driven, unloaded, back to the loadout area. The pavement had been wetted to suppress dust. Employee was traveling too fast, swerved to miss a pallet in the line of travel. Forklift spun 120 degrees. His right rear wheel slid into ditch and the left rear side of the forklift climbed a berm along side of ditch. Forklift overturned on its right side.