Originally established in 1949 as a fishing company, Petuna diversified into aquaculture in 1990 and is now one of Australia’s largest domestic retail suppliers of salmon. Their marine farm at Rowella on the Tamar River employs around 25 people, where salmon are nurtured in pens for approximately 15 months before being harvested for the consumer.
With strong river flows and tidal movements, the Rowella marine farm has a continual supply of well oxygenated water. It also boasts beneficial biosecurity and environmental outcomes, given its isolation from other marine farms. The walkways that link the farm to the shore make it unique to other marine sites, allowing feeding and harvesting without the need for boats.
Over the last 20 years or so, the Rowella marine farm grew organically, from two polar circles, to comprise of 30 x 24m pens. While these expansions were operationally and technically sound, they were ‘pieced together’ add-ons. With improvements in fish health, operational ability and mechanical advances, it was clear that the farm would greatly benefit from a complete re-design. As such, the entire Rowella marine farm was upgraded to 22 x 36m pens.
Valmont Coatings hot dip galvanized the new pens, which were comprised of large Parallel Flange Channel (PFC) base frames, with walkway mesh welded onto the surface. Each frame was approximately 12m long and up to 3.4m wide, requiring double dipping. Valmont also galvanized a range of smaller components like lugs, poles and fittings.
According to Marco Bazzano (Sales Manager Victoria and Tasmania, Valmont Coatings), “Galvanizing was used for the Rowella marine farm for its durability. The years to first maintenance and longevity of galvanizing are second to none. Galvanizing can look fantastic if designed and prepared correctly—painted, tarred and plastic finishes just don’t look as good.”
Innovation in Design
Bazzano described how Valmont’s involvement during the design phase delivered several benefits to the project.
“We were heavily involved in the design of the platforms from a galvanizing perspective, this was to ensure the best galvanizing practises that all components were designed around ensuring all surfaces were coated correctly and adhered to meeting standards.”
Logistics and Installation
The project timeframe was critical. The day-to-day operations of the Rowella marine farm continued as usual while the existing 24m pens were removed, and the new 36m pens were installed. This meant that construction and installation had to adhere to strict timelines to ensure that production at the marine farm was not adversely affected.
The strict timeframe was compounded by various site constraints. The site area itself was very tight, with minimal flat hard standing ground. Truck access was difficult, with the construction area itself also doubling as the only route in and out of the marine farm.
The tides only allowed a six-hour window for removal of the existing pens and installation of the new pens. If a new pen was not moored off prior to the tide turning, the structural integrity of the farm was placed in significant danger.
“The installation of the pens was no mean feat. The Installer had to wear a wetsuit, and jump into freezing cold waters—where the temperature is only about 7°C. The frames and walkways were bolted onto permanent floats and floated out into place for installation. When carrying out this type of installation in the middle of Winter, parts of your body can go numb,” said Bazzano.
Finally, the walkways were manufactured in Launceston, shipped across to Melbourne for galvanizing, and then shipped back to Launceston. This presented a series of logistical challenges, given the considerable number of moving parts.
“Valmont adhered to strict completion times so that the products were on time for the correct ship sailings. Our production scheduling and throughput efficiencies in the plant made this possible,” said Bazzano.
Teamwork and Collaboration
As Bazzano describes, teamwork and collaboration were essential to the success of the project. “The highly effective design of the new pens was made possible through collaboration with the farm, the fabricator, the designers and architects and us—the galvanizers.”
“Teamwork was absolutely paramount in this project. There was daily communication between the galvanizer, the fabricator and Petuna Group. The reasoning was that cranes and teams were specifically locked and loaded on set days, all based on tides and water flow for the installation to proceed.”
“Attention to detail and passage of information were key—it was imperative that everyone involved had ‘buy in’. The active involvement of the entire team ensured that the project was extremely successful,” said Bazzano.
Given the success of the Rowella project, there is ample room for future market growth across salmon farms generally, and particularly in Tasmania. It is expected that extensions and reconfigurations of existing salmon farms will grow due to increasing demand for the product. Valmont Coatings is already in discussions for projects over the next two to five years, and beyond.
Project Team
- Developer and Owner: Petuna Group
- Head Contractor and Fabricator: Crisp Bros.
- Hot Dip Galvanizer: Valmont Coatings (Melbourne and Launceston)
- Pontoon Manufacturer: Mitchell Plastics