New Robotic Inspection Technology Helps ID Potentially Critical Situation

By Jeff Griffin, Senior Editor | May 2009 Vol. 64 No. 5

Early this year, water officials in Toronto, Ontario, Canada, became aware there were cracks in one of the city's primary large diameter sanitary sewer trunk mains that threatened the Don River watershed and homes in one neighborhood.

A potentially disastrous impact on the area and its environment could develop if the aging 114-inch pipe should become blocked or collapse.

The three mile long Coxwell Sanitary Trunk Sewer, described as the city's most critical trunk sewer section, was built in the 1950s and serves 750,000 residents typically carrying more than 105 million gallons of sewage per day to the Ashbridges Bay treatment plant.

The first step in determining how to address the problems was to confirm the locations and extent of damage.

However, because of the sewer's 140 foot depth, the long distances between access manholes, and high flow velocities, detailed inspections and condition assessments had not been possible, Lou Di Gironimo, general manager of Toronto Water Services said at a public meeting in January.

To inspect the line and develop a plan to fix the as yet unknown problems, the city called on trenchless sewer rehabilitation specialist DM Robichaud Associates Limited, Oshawa, Ontario.

"We received a call asking if we could inspect the Coxwell Trunk Line as they believed there was some kind of anomaly in the line from a previous incomplete inspection," said Earl Brousseau, senior project manager/owner. "The city initially believed that no equipment would be able to reach the reported anomaly due to the high, fast flows, great depth of the trunk line, and the one mile length between access manholes."

Previous experiences

DM Robichaud had recently completed a pilot project and inspected 11 miles of sewer trunk lines using RedZone robotic multi sensor equipment. City officials asked if the equipment could be used to perform inspections to determine the extent of the anomaly's deficiency that another contractor had been unable to complete using conventional inspection methods.

Brousseau said the unique RedZone Robot is equipped with multiple sensors, including traditional pan and tilt closed circuit television camera, sonar for seeing below the water line, three dimensional laser for measuring pipe ovality and precise surface abnormalities, hydrogen sulfide sensor, inertial measurement unit for line and grade, and water depth sensor. All sensors record continuously and are synchronized over the pay-out distance.