The city reports that emergency repairs were necessary after a break in the pipeline that supplies treated effluent to Alder Ranches Ltd. at the spray irrigation site a month ago.
The break released a significant amount of water that caused a large washout and cavity five to eight metres in depth near the bottom of a steep slope. Several areas along the pipe alignment upslope from the cavity to Kelly Road have collapsed or partially collapsed, according to an administration update presented to city council.
Further investigation showed that water had been flowing alongside the pipe, causing erosion, slumping, void space and leading to the collapse and washout.
The cavity, estimated at 300 metres-cubed, was filled in a week ago and parts are currently being sourced to supply the ranch with water for a second seasonal crop through an overland firehose service.
A geotechnical study has already been completed and permanent repair solution is in the works, with construction anticipated to start later this summer.
The city estimates the cost of the work to date, as well as the temporary and permanent solution, is approximately $400,000.
Mike Matejka, the city’s Manager of Infrastructure Planning & Delivery Division, said factors such as a poor initial design and construction when it was installed roughly 30 years ago were responsible for the break.
“The installation method that they used would have been suitable for a level ground or a more mild slope, but it was about a 50 per cent slope; it was hard to climb up, and the pipe they used did not have any restraints or trench dams in it, which would have been good engineering practices,” Matejka told council. “…so when there were some issues with some erosion around the pipe and some water eroding around there, there wasn’t anything holding the pipe together and essential the weight of pipe and the material in it would have just pulled it apart.”
Funding for the repairs is being sourced out of $500,000 earmarked for the 2019 sanitary sewer road program budget as part of a $8.2 million grant submission, in which the city has to pay 10 per cent. The grant application has been submitted to the province but a funding announcement isn’t likely to be made until later in the year.
If the city’s grant application is successful, $500,000 of the 10 per cent contribution will be siphoned from the sanitary sewer fund surplus — a fund that is expected to reach $3.9 million by the end of the year and well in excess of the city’s target of $2 million.