Concrete Bar-Wrapped Cylinder Pipe (C303) Condition Assessment Increases the Reliability of the City of Calgary's Water Infrastructure

In July of 2011, the Rundle Feedermain, a 24-in. (600-mm) C303 concrete bar-wrapped pipe (BWP) transmission main, failed in a residential neighborhood in the City of Calgary (the City). Residential development had cropped up around the feedermain since its construction in 1973. Although the main is located in an easement, the exact break location was 9 ft (3 m) west of a residential property line. This increased the main's consequence of failure, as additional ruptures may cause serious damage to private property. To return the Rundle Feedermain to operation, the City commissioned Pure Technologies (Pure) to complete an emergency inspection of the pipeline. Pure mobilized available inspection platforms to examine the line upstream and downstream of the failure location to ensure that no other pipe sections were at risk of rupture. The inspection used a robotics platform equipped with Pure's electromagnetic (EM) technology, which is able to identify broken bars and broad areas of cylinder corrosion in BWP. The emergency assessment identified four additional areas of distress and allowed the City to repair a second section of BWP that was likely to fail had the pipeline returned to operation. After the successful inspection of the Rundle Feedermain, the City of Calgary began incorporating BWP inspection into its biannual feedermain condition assessment program. Due to this shift in focus, in August of 2013 the City excavated one section of 30-in. (750-mm) BWP that was identified as badly distressed during the inspection program. The excavation verified that the pipe had broken bars and cylinder corrosion and was a candidate for near-term failure if left in operation. Due to the various operating conditions encountered in the program and with the City's cooperation, Pure has been able to refine and improve BWP inspection technology and apply it to multiple inspection vehicle platforms to assess the City's BWP mains. Through condition assessment, the City is able to identify and repair isolated damaged pipe sections on otherwise serviceable pipelines. This prevents unnecessary and expensive main rehabilitation or replacement, while renewing the condition of the City's critical large-diameter pipeline assets. This paper will outline Pure's BWP inspection technology based on two projects in the City of Calgary and include actual results from field verifications of the electromagnetic inspection data.