Case Study of an Innovative Forensic Investigation of a Dramatic Pavement Failure, 14 Street NW, Calgary, Alberta.

On the evening June 5th, 2007, the City of Calgary experienced an extreme weather event; over 70 mm of rainfall, much of which fell within one hour. This resulted in significant consequences in terms of surface runoff, storm sewer capacity and other related pressures on surface and subsurface infrastructure. Likely the most dramatic of the damage was the resulting distress to an approximate one kilometer section of 14 Street NW, a primary north/south commuter corridor accessing the City downtown core. Surface damage included severe upheavals in both the roadway and adjacent sidewalk, the extent and magnitude of which required closing of the facility to both vehicles and pedestrians. The City of Calgary, Roads Division, commissioned EBA Engineering Consultants Ltd. to undertake an integrated pavement and subsurface assessment program. This included Road Radar™, geotechnical Ground Penetrating Radar (GPR) and Falling Weight Deflectometer (FWD) testing. This information was supplemented with detailed visual surveys and interviews with City personnel. In addition, the City undertook assessment activities such as video inspection of sewer installations. This paper describes the innovative pavement assessment methodology and data presentation features, along with the methods used to identify the cause, nature and extent of pavement and subsurface distress. The design concepts employed for the necessary restoration are provided as well as several innovative project delivery concepts and construction details. These aspects were focused on addressing the impacted infrastructure, mitigating the reoccurrence of this phenomena, and fast-tracking the project to minimize traffic disruption on this primary route.