Dredging the Port of Melbourne shipping channels
The Gateway has begun dredging the Port’s shipping channels. The Port of Melbourne is required to maintain the declared navigable depth of the channels. The need for dredging the channels is ongoing. Dredging has been part of the Port’s work for over a hundred years.
The Gateway is a Trailer Suction Hopper Dredge owned by Boskalis, a global company based in The Netherlands. Boskalis specialises in dredging, both maintenance and capital.
Boskalis’ Queen of the Netherlands undertook the Port of Melbourne channel deepening project between February 2008 and November 2009.
Equipment on the Gateway drags material from the floor of the shipping channel which is then sucked like a vacuum cleaner into the hopper. The hopper has a capacity of 12,000 m3, much greater than dredges formerly used for the work. The dredged material is then taken to the Port of Melbourne Dredged Material Ground.
Work began at the end of May and will proceed for about 7 weeks with expected completion in early July. The dredging will proceed 24 hours a day, 7 days a week.
The Port of Melbourne’s ten year maintenance dredging programme must proceed in accordance with an approved Environmental Management Plan. Turbidity is an important consideration in the EMP.
The level of turbidity generated by dredging must be closely monitored. Reduced light associated with turbidity can adversely affect the health of seagrass which is a nursery for fish.
Dredging activities must also conform with EPA noise requirements.
There was no EPA, and no noise requirement, when the Melbourne Harbor Trust’s A D Mackenzie dredge kept the Yarra shipping channels clear in the 1970s. The A D Mackenzie, unlike the Gateway, was a bucket dredge. Its moving buckets made a noise that is one of the memories of growing up in Port. One person described it as being like finger nails on a black board. The clanking noise was heard most clearly at night in Port’s neighbouring communities.
Closer to the city, a novel vessel known as Geoff is at work turning a water wheel on the Yarra Birrarung. Geoff is anchored in a high profile position near the Aquarium, just off Spencer St. The flowing River turns the wheel and litter passes through to a bin. A solar panel triggers a notification to Parks Victoria when the bin is full.
It is a trial, an initiative of Ocean Crusaders, a group that is as inventive as it is determined to keep litter out of the marine environment.
The bin will be much easier to empty than the cumbersome method of emptying the Bandalong litter traps. The video below (22 secs) shows the time consuming, labour intensive and very inefficient process. Small material, such as microplastics and polystyrene easily escapes the grab’s clutches.
So much trouble, so much expense to keep litter out of the Yarra Birrarung and the Bay.
Look out for the Gateway and Geoff at work on the Bay and in the River.
Port of Melbourne Dredging Program 2023 – 33 (DP23-33) Environmental Management Plan
Parks Victoria About Geoff, the automatic river cleaner