Underwater Sewer Pipe Inspection

By Jeff Griffin, Senior Editor | March 2012, Vol. 67 No. 3

In 2011, Interactive Pipe Inspection (IPI) completed inspection of more than 50,000 feet of 30- and 48-inch diameter sanitary sewer lines for King County, WA.

What sets the project apart from routine pipeline inspections is that the sewer lines were underwater in Lake Washington and Lake Sammamish.

IPI specializes in pipe inspection and assessment services using panoramic pipe inspection technology that provides a 360-degree look at inside pipe surfaces and detailed information far beyond the capabilities of conventional pan-and-rotate inspection cameras and equipment.

Sewer lines inspected were:
• Issaquah Interceptor, 14,673 feet;
• Holmes Point Trunk,11,665 feet; and
• Kenmore Interceptor, 24,497 feet.

Bryce James, IPI manager, said the sewer lines were laid more than a half century ago, initially flowing directly into the waters of the lakes. In the mid 1960’s, the lines were diverted from pump stations along the lakes into interceptors and trunks sending raw sewage to treatment plants.

The inspection equipment used was an Inuktun VT300 Versatrax crawler/camera system with multi-sensor capability, said James, adding that IPI is only one of four companies in the United States with this inspection system.

With three cameras and multiple sensors, the Inuktun Versatrax 300 is the solution to long-range pipe inspection, said James.

“With it,” he explained, “IPI is able to inspect more than 6,000 feet of pipe in a single run, the first time this has been done in the United States using a high-resolution, 525-line resolution CCTV camera. This capability not only saved the crew the time and coordination effort of moving the dock to many different sites, but also saved King County money, compared to costs of previous inspections using equipment that would have had to make many, much-shorter runs.”

To implement pipe inspections with the VT300 in the underwater work environment required two experienced IPI crews, supported by certified divers, a portable dock, boats, a caisson to access underwater manholes and other support equipment.

Special procedure devised (subhed)

James summarized the steps necessary to perform the inspections. The first step was preparing the portable dock to use as a float and home base.

“We were unable to use a barge because the manholes in the lakes were too close to the shoreline,” he said. “The dock was outfitted with a cover for protection against both sun and rain, and then the equipment was brought onboard. Tether reel, electronic control and recording equipment were set up on the dock.

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