Enid Water Treatment Plant Addresses Challenging Repair of 30-Inch Pipeline

The city of Enid, Oklahoma, operates a two-stage active sludge system treatment plant which treats 2.3 billion gallons of wastewater annually with a primary goal of compliance with National Pollutant Discharge Elimination System (NPDES) permit. Following a recent inspection, sections of a 30-inch bar-wrapped pipe were identified as being close to imminent failure. Without this critical line, the city’s treatment plant could not operate and planning for repair needed to begin immediately following identification of the distressed area. A challenge identified early in the process was that the line could not be shut down to perform the repair. In addition, the distressed area of the 30-inch pipe was located on the interior of a subsurface vault, in a highly congested area. These factors, along with others, limited the number of repair options which would be viable. After consideration of all, carbon fiber applied externally to the distressed segment of pipe was the most feasible option to provide a fully structural repair. This paper will provide a detailed view of this challenge faced by the city of Enid and their process from inspection through repair of the critical pipeline within the vault structure. Technical details on the use of externally applied CFRP for fully structural repairs of pipelines is discussed.