Geotechnical risk assessment for buried infrastructure in Regina

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Regina, Saskatchewan is situated on an expansive clay deposit possessing high volume change capability. TransGas Limited is responsible for providing natural gas through a pipeline network (comprising 1160 km of mains and 78180 services) that is supported by the indigenous clay. Alternate shifting movement in the expansive soil has severely affected buried infrastructure systems. The pipe failure rate in the city ranges between 40-110/year with an annual average of 65. Based on past experience, the company has recognized the significance of periodic soil deformations as the main factor influencing pipeline integrity in Regina. Departing from routine practice of conservative design (based on site-specific and time-specific approaches), this research proposes a comprehensive investigation of the volume change problem. Locally, swelling and shrinkage is governed by the following parameters: soil properties (conductivity, saturation); ground cover (vegetation, pavement); climatic condition (precipitation, evaporation); and hydrologic condition (drainage, ponding). The main objective of this research is to develop a geotechnical risk assessment method for management of buried infrastructure in Regina. The research methodology broadly comprises two main activities, namely: description of uncertainty and estimation of hazard. The transfer of technology from academia to the company will be in the form of a technical report that will contain the geotechnical risk assessment method as the end-user deliverable. The applicant will also be available to assist TransGas Limited to integrate the newly devised method into routine practice. This project will help TransGas Limited to achieve the following: (i) minimize the number of leak surveys and (ii) prioritize critical areas of interest. The new risk assessment approach (which captures the effects of soil, cover, climate, and hydrology) will be beneficial in reducing the geotechnical hazards, operational costs, and social uncertainty associated with the natural gas distribution system in the city. The findings of this research will be applicable to other buried utilities (water supply and sewage collection) in Regina and will also be useful to other communities in Canada with similar issues.