The City of Sioux Falls selected Banner to conduct a study on rehabilitation methods of unlined metallic water transmission mains. The existing unlined iron pipe (cast or ductile) can develop deposits, contributing to red water issues. The operations staff have had a few emergency repairs on the large diameter transmission mains. A pilot project was completed near the City’s Water Purification Plant. The water transmission mains were located in hard to reach locations: some ran through the Maguire Iron yard, beneath railroad tracks, under an electrical substation, in close proximity to the City's ground storage reservoir, and in the Airport. This made standard open-cut replacement less than ideal for the project. After evaluating alternatives, a Class III Structural Spray in Pipe Liner (SIPP) process was selected for the construction method, which included a thorough cleaning of the pipe interior to remove deposits and nodules to provide a smooth, clean surface. A polymer lining material was then adhered to the smooth pipe interior. In total, over 3,000 feet of 20”- and 16”-diameter water transmission mains were rehabilitated using SIPP during the project. This was the first project of this type performed in South Dakota.