A duct assembly for flowing fluids includes a first duct positioned above the ground. The first duct is configured to flow a first fluid. In addition, the duct assembly includes a second duct positioned above the ground. The second duct is configured to flow a second fluid. The first duct and the second duct isolate the first fluid and the second fluid from each other. Further, the duct assembly includes a stand supporting the first duct and the second duct above the ground. The stand has an upper end positioned below the first duct and the second duct.