WASTEWATER
High tides among the obstacles faced during Vancouver Island force main inspection By Mark Fodchuk and Justin Hebner
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ometimes the catalyst for a pipeline inspection can come from an unexpected source. In this instance, the story began when it was noticed that a sewer pipe was exposed because of erosion during low tide along the beach. That observation set the wheels in motion for an eventual inspection of a critical force main that services approximately 41,000 residents in both the Town of Comox and the City of Courtenay on the eastern coast of Vancouver Island, British Columbia. The pipeline was installed in the early 1980s and consists of an 8.75 km large-diameter force main that connects Courtenay, Comox and K’ómoks First Nation Community to the Comox Valley Water Pollution Control Centre. This includes a 5-km portion buried in an “intertidal” foreshore section (area between high and low tide). Over time, a section of beach eroded and exposed the line to coastal wave action (high tide hides the pipe). The Comox Valley Regional District (CVRD) took steps to restore the beach section where pipeline had been exposed, and began developing plans to relocate the exposed force main off the foreshore. A new concept was developed that would utilize a portion of the existing force main within the foreshore, but remove from service the exposed portion. Due to its sensitive location and the environmental consequences of a potential failure, the CVRD elected to complete a highly specialized pipe condition assessment on the entire length of the line, to better understand remaining service life and overall condition. The project timeline was tight as CVRD needed quick results to proceed with corrective action immediately should it be required. The inspected portion of the pipeline was built of two different materials, prestressed concrete cylinder pipe and barwrapped pipe, and three different pipe 18 | December 2018
(Top) Inspection crews had to work quickly and deal with the rising tide. (Left) Retrieving the PipeDiver inspection system. (Above) Analyzing data gathered by the SmartBall.
diameters: 450 mm, 750 mm and 820 mm. As well, the critical line could not be taken out of service. Associated Engineering, CVRD’s consultant, assisted in developing the request for proposal process. Pure Technologies, part of Xylem Inc., was selected to conduct the condition assessment. This included an electromagnetic inspection, structural curves, leak and gas pocket detection, and transient pressure monitoring. Pure Technologies proposed using its acoustic-based SmartBall tool for the leak and gas pocket detection, and its free-swimming PipeDiver inspection
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platform for the electromagnetic inspection of the line. Transient pressure monitors were installed at the Courtney Pump Station. For more than four weeks, recorded pressure data was used to understand the operational and surge pressures within the force main and their impact on structural integrity. While transient pressure data was being collected, Pure Technologies deployed SmartBall, a multi-sensor tool used to detect and locate the acoustic signature related to leaks and gas pockets in pressurized pipelines. The tool has the abil-
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