Posted on September 19, 2016
By Matthew Bingley, CBC News
New hydrographic boat purchased to combat sediment through future dredging operations
The Port of Saint John has a new vessel which will allow it to continue mapping the ocean floor in order to tackle the tricky task of removing two constant sources of sediment.
The hydrographic survey vessel, named the Tide Line, cost the port authority $416,000. The 30-foot aluminium boat is in itself expensive, but the most costly portion is the sonar equipment. The sonar head alone cost more than $100,000, which doesn’t include the retractable arm it is mounted on.
Still, the port authority’s harbour master and vice-president of operations Chris Hall said the equipment is a necessary part of its operations.
“The harbour is continuously in-filling with silt that gets deposited from the river and the incoming Bay of Fundy,” he said.
In order to stay ahead of the natural process, the port needs its own vessel to map the sea floor.
Ottawa provided services
In the past, the services were provided by the federal government. Hall said that process was inefficient because data was usually out of date by the time it was received by dredging contractors.
“Being able to perform the surveys on a timely basis is of critical importance” said Hall.
For the past 10 years, the Port of Saint John leased a survey vessel through an agreement with the Fisheries and Oceans Canada. Before that, the port depended on data provided by the federal government. The federal department shared the vessel with the port in exchange for the information it gathered.
Hall said at 30 years of age, it was time to purchase a new vessel and buying it through port revenue would be more efficient.
Crew of two
On board the Tide Line, a crew of two can easily patrol the harbour to map the ocean floor. Quite similar to many other fishing boats, the main difference is the desk set up on the cabin’s port side. A computer attached to the sonar equipment allows hydrographer Alec Ketchum to see real-time data displayed on two monitors.
The images are so detailed, Ketchum said the differences before and after dredging can easily be spotted.
“You can see quite evidently where the dredge has removed material, you can see the little claw marks from the dredge,” he said.
While the data is eventually passed off to the port, Ketchum said the onboard computer can build detailed models of the ocean floor in about an hour.
The day-to-day details aren’t as easily spotted, said Ketchum, but without regular dredging sediment can quickly build up. Over a six-month period in Courtney Bay, Ketchum said “It could infill by 80 centimetres, 100 centimetres.”
However, those figures are variable, changing each year, regardless of weather patterns.
The Tide Line will soon be put through a rigorous test in the next year as the port begins its west side modernization program. Significant dredging will take place along the piers and in the main channel, taking it from a depth of 8.4 metres to 10 metres.
“This vessel will play an absolutely critical role in that operation” said Hall.
Source: CBC News