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of various pilings, piers and walls. However, in murky or low-visibility water, this amounts to hunting and feeling around in the dark, like the proverbial blind man describ- ing an elephant.

Today there is a better way. For the first time, port authorities can now gain detailed visual documentation of underwater infrastructure conditions to analyze and archive. This is something that was not even possible until more advanced scanning sonar technologies began to be applied to map out harbour floors, piers and docks. Prior to this advance, in most cases port authorities relied on descriptions of a pier’s sub-surface state from divers feeling around blindly in zero-visibility conditions. Clearly, sonar represents a significant addition to the port manager’s insurance risk management toolbox.

Managing the Port’s Insurance Risk

How can sonar be used? According to Abbott, in a proactive maintenance campaign, sonar is used first to map out and image the various targeted infrastructure items to develop a baseline foundation of the port’s cur- rent condition. The harbor floor bottom around docks and slips, and out into the harbor, should be included, and a composite map drawn up that shows all the unusu- al items on the sea floor. (These can range from vehicles, dropped containers, lost suitcases and shopping carts to mishandled cargo and enormous concrete blocks.)

In addition, side-scan sonar enables the real-time view- ing of underwater pier walls buckling either in or out, any damage or deterioration, and the state of support pilings and their bases; in addition, the sea floor underneath docks can be imaged. Electronic pictures of all of this information, once created and saved, can then be assem- bled into a mosaic for easy viewing and analysis by port management at their desks, and subsequently printed and archived electronically as a baseline study for future main- tenance budget planning.

In Portland, Oregon, for example, city engineering offi- cials charged with maintaining the sea wall along the

Willamette River had underwater surveying expert Brian

Abbott of Nautilus Marine Group use sonar to develop a composite underwater image of the entire wall. They were able to use this to establish a visual baseline record of pos- sible weak spots and develop a program of maintenance work. “What’s valuable is that you can go back down in a couple of years and take similar images,” notes Abbott. “Then compare over time to see the changes when you need to prioritize your always-tight maintenance and cap- ital budgets.” “With advances in sonar computing technology, the res- olution and quality of underwater images is now quite high. It’s very eye-opening for port managers,” notes

Kongsberg’s senior projects’ manager Mark Atherton, also the author of the upcoming textbook Visualization of

Underwater Structures Using Scanning Sonar, and an expert in the field. “Sonar is the port manager’s portal for viewing and monitoring the state of the port’s substantial underwater infrastructure assets.”

Most ports have regular survey programs involving divers going down to check out underwater structures, pil- ings, bridge supports and pier walls. The problem is that, in murky conditions, visibility is poor and divers are forced to feel around blindly, raising quality-control and safety issues.

At the Port of Montreal, one of the largest port authori- ties on North America’s eastern coast, geomatics engineers have already used sonar to conduct a survey of the port’s underwater infrastructure. The goal was to establish a baseline not only for maintenance plans, but also for future infrastructure expansion.

The current economic situation, where global trade and 24 MTR September 2010