Dredging & Dolphins!

Keen port watchers, Freo to Perth and Perth to Freo train passengers, ferry passengers to and fro Rotto, and boaties will recently have noticed TRUD R, a blue and red hopper dredger, moving around Fremantle’s Inner Harbour or mysteriously travelling back and forth from and to Gage Roads.

Credit Fremantle Ports

Well, the TRUD R is a 75 metre long Danish dredger and she’s been removing sediment to ensure the Inner Harbour continues to be navigable for the large container ships that visit Freo.

TRUD R has been hard at work since 15 April and finishes tomorrow, Friday, 3 May.

The project was originally scheduled for 10 days, but had to be extended by a further 7 days lastly for … dolphin pauses!

The dredging has removed sediment that has accumulated in the Inner Harbour since the previous dredging carried out in 2010.

The project involves a total dredge volume of some 80,000 cubic metres over five years. Specifically, 60,000 cubic metres of the sediments will have been removed during the current dredge, with a further 5,000 cubic metres to go annually from 2025 until 2029. The amount being dredged is just 2 per cent of what was removed from the harbour when it was deepened in 2010.

Lots of sediment!

The dredged sediments are taken out to the Gage Roads offshore disposal site, which was used during the 2010 project and is in line with an Australian Government approval.

TRUD R off Fremantle, 19 April 2024. Credit Graeme Waller and. Easel Finder

Maintenance dredging is essential to ensure safe access for ships into the Inner Harbour and to maintain berths deep enough for the larger container vessels that visit Fremantle.

Fremantle Ports has engaged marine consultants to conduct environmental investigations and assessments, including sediment sampling, plume modeling, and seagrass mapping. Dredging in autumn reduces the impact on seagrass as this is its dormant stage.

The TRUD R received a Welcome to Country and was involved in a Smoking Ceremony before work commenced. Respecting country and wildlife in and around the river was an important consideration during the project.

While port watchers have pondered the trailing suction hopper of TRUD R steam back and forth the Inner Harbour over the past fortnight hoovering the high points of the harbour bottom, the vessel’s also been an attraction for the resident dolphin population.

Credit Fremantle Ports

“We’ve had to pause dredging operations quite a few times because dolphins have been in the monitoring zone,” said the port Manager Communications and Community, Neil Stanbury.

‘The good news is they seemed content and happy, with the dredging not showing up changes in their foraging behaviour in the harbour,” Neil said.

“But it’s meant we’ve had to move out of certain areas at times to create some distance.”
On one of the transits returning from the Gage Roads dumping area back into the harbour, a sea lion, also took a liking to the dredge.

Credit Jean Hudson

“It’s hard to say what the exact interest is, but more than likely the sediment around the dredge indicates possible feeding opportunities for these species.”

Fremantle Ports employed Noongar marine species observers aboard the dredge and support vessel to watch for wildlife.

“It was a great initiative, because we helped them gain qualifications and experience and it was another step forward by the Whadjuk Aboriginal Corporation towards its goal of a broader Swan River ranger program, which Fremantle Ports thinks is a very positive concept”.

The Swan-Canning river system is the permanent home to more than 20 dolphins and with salmon and bream teeming in the harbour right now, pods are currently spending a lot of time downstream of the traffic bridge.

The port’s free harbour tours over the past two Sundays have seen continual dolphin sightings – those tours finish this Sunday.

Port Hydrographer Jay Illingworth said the dredging was wholly between the Fremantle Traffic bridge and the ends of the moles. He explained that water didn’t simply flow out of the river in a straight line, but meandered, as it’s done for millennia. This meant most dredging was required at the eastern end of the harbour.

“A lot of the sediment comes through the southern bridge span and is washed in through the tide and ends up settling in that area.

“It’s interesting to see the patterns of sedimentation over time and it’s consistent with the old paleo (ancient) channel as it was once known as, which was the way the river runs from the bridges out to the ocean.

“A lot of river sediment has deposited in the southern corner of the 14.7m basin adjacent to container terminal 4, just off the tug pen.

“Container terminal 4, the eastern-most one, has suffered a lot of deterioration due to sedimentation and the corner of that is only declared at 13 metres, which is a pretty decent constraint on the use of that berth,” he added.

Since 2010, the harbour has had a working depth of 14.7m, meaning it can take the largest container ships visiting Australia, but the river floor is constantly changing, with ships’ propellors and tugs continually creating high points.

Plumes of sedimentation have mostly been within predicted areas, though one band went as far upstream as Freshwater Bay. Port water quality monitoring has been conducted throughout the program, with more after dredging finishes.

Jay said Fremantle was, compared to many ports, a fortunate one.

“We are very lucky, because it’s a very stable environment within the Inner Harbour, however we haven’t been doing dredging but now we are planning to do it regularly to stay on top of that “sedimentation.

Not doing the maintenance dredging would have ended up with more restricted areas for shipping, with less ‘searoom’ for manoeuvring ships.”

By way of example, the Port of Brisbane continually dredges, while the Port of Newcastle owns its own dredge. Fremantle does not, with the TRUD R contracted in for this project. The TRUD R’s next destination is … Newcastle!

With thanks to Neil Stanbury* and Jean Hudson**

* Neil Stanbury is Fremantle Ports Manager Communications and Community

** Jean Hudson @jeansodyssey is our Shipping Correspondent and also a regular feature writer and photographer here on the Shipping News. You may like to follow up her informative Places I Love stories, as well as other feature stories and Freo Today photographs, right here.

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