Underwater Sewer Pipe Inspection

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

IPI spilt personnel into two crews. One crew operated from the base dock. Using project maps, the crew would take a boat to the position marking a manhole and a certified diver would locate the underwater manhole and mark its spot with a buoy.

The second crew in another boat then would tow a 48-inch caisson supplied by King County to the buoy and lower the caisson into the water. A diver would help guide the caisson into position on the manhole platform, attach it to the platform, and water would be pumped out of it to form a sealed “chimney” to access the manhole cover and pipes. Once in place, safety floats were attached to the caisson.

The first (inspection) crew then moved into position at the caisson. The camera component was lowered down the chimney/caisson and into the pipe and the inspection process was initiated. IPI had to invent and manufacture special winches to attach to the caisson in order to lower the camera into the pipe.

The Versatrax 300 moved through the pipe, and its 360 degree findings were relayed in real time to the home base equipment on the dock and recorded for future inspection diagnostics. A portable hard drive was used to store the information and then delivered to the county.

Data collection (subhed)

Infrastructure Technologies’ I.T.pipes software was used to collect the inspection data and document findings. I.T.pipes database and application were designed to seamlessly integrate with other applications, including ESRI GIS. I.T.pipes is a certified NASSCO PACP software.

After inspection of a section of pipe was completed, the second crew returned, the diver unlocked the caisson, it was filled with water, an air plug was inserted and inflated, and the caisson was towed to the next site where the process would be repeated.

Being able to utilize information from King County’s maps directly with I.T.pipes data was instrumental in finding several previously unknown problems.

“For example,” James said, “we located a missing manhole at Holmes Point by linking the map with the inspection data. We also found multiple occurrences of incorrect pipe sizes and lengths that we immediately corrected in the geo database, allowing us to track the project. These findings were corrected within IPI’s version of King County’s map files, based on the communication between I.T.pipes and the GIS.”

James said the reports are clear and easy to understand by anyone needing to evaluate them.

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