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This paper discusses the City of Calgary, Alberta, Canada's experience with a 1200 mm concrete water feedermain rupture in January 2004. Thisfeedermain services a large pressure zone in the northeast sector of Calgary,servicing approximately 100,000 people. Within a few hours, pressure problemswere reported throughout the pressure zone, and a major hospital was alsoreporting severe pressure problems. Fortunately, the water pressure wasrestored to the area within a few hours of the break. When the break was located, the extentof the damage was discovered and it was obvious that the concretehad severely deteriorated, and the pre-tensioned steel had virtually corrodedaway. Anelectromagnetic survey of the steel was done to determine if there were additional steelwire breaks in the feedermain and three additional locations were discovered to need repairs. Several engineering investigations were undertaken to determine the cause ofthe failure, including soil testing that indicated extremely high sulphate levels, which combinedwith the groundwater conditions led to the deterioration of the concrete, and theeventual corrosion of the steel. Ahydrophone device was installed in the feedermain to "listen" for additional wiresbreaking. To the end of December 2004, 36 individual wire breaks have beenheard. Test pits combined with soil results will be used to determine the limitsof the replacement. Polyurethane-coated steel is being considered for thereplacement at an estimated cost of $2.5 million. Includes 8 references, figures.

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Edition: Vol. - No. Published: 06/17/2005 Number of Pages: 18File Size: 1 file , 620 KB