Infrastructure owners must decide between rehabilitating or replacing aging assets, however, appropriate asset health information is simply not available for certain structures. An asset class identified by The Ontario Good Roads Association (OGRA) that presently lacks health information is major roadway pipes (culverts). A critical culvert failure mode is due to the formation of undermining or voids behind the culvert wall caused by soil erosion. The level of “undermining” is currently not measured when evaluating replacement or rehabilitation possibilities. This information gap is of particular concern for planning “slip-lining” or other rehabilitation projects since significant undermining compromises the culvert’s fundamental structural integrity. Lack of complete integrity information can lead to unnecessary and costly replacements, and poses a risk to public safety. During the summer of 2011, OGRA supported an integrity analysis pilot project on selected roadway culverts using recently-developed inspection equipment capable of quantifying undermining. This new modality, Backscatter Computed Tomography (BCT), is a practical in-situ form of Computed Tomography also known as a CAT Scan. The purpose of the pilot was to evaluate the technology’s potential to measure undermining, thereby facilitating the planning of major roadway culvert replacements or rehabilitation. Three culverts in the City of Toronto were inspected to determine the culverts’ structural condition using BCT equipment provided by Inversa Systems Ltd.
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