Repair of a Punctured 48 in. Diameter Prestressed Concrete Cylinder Pipe on a Sixty Degree Slope

A directional driller punctured a buried 48 in. diameter potable water prestressed concrete cylinder pipe (PCCP). The pipeline is part of the City of Columbus (OH) Division of Power and Water system which supplies water to 1.1 million people in the region. The 4 in. diameter puncture occurred below the water level of a creek on a 60 degree slope as the pipeline alignment turns up from the creek crossing adjacent to a bridge abutment. Due to environmental issues associated with the creek and its banks, the lack of access caused by the steep embankment, presence of a large concrete thrust block at the outside of an elbow at the top of the embankment, various utilities, and proximity to the bridge abutment, the pipe could not easily be excavated and repaired from the outside. This paper presents a case study of damage assessment, repair design, and internal carbon fiber reinforced polymer (CFRP) repair construction. Damage assessment included inspection of the pipeline damage area and nearby elbows and joints, and evaluation of the effects of the puncture and soil washout on the pipe and risk of thrust restraint failure. Considerations for the repair design and construction included the 150 psi design working pressure (250 psi working plus transient pressure), stopping the creek water inflow prior to construction, restoring the integrity of the steel cylinder on the lined cylinder pipe, and performing concrete surface preparation and installation of the CFRP repair inside the 48 in. diameter pipe on the 60 degree slope.