Whale experts have raised concerns that construction works on the new Granite Island Causeway have the potential to affect endangered southern right whales and drive them away from Encounter Bay's whale nursery.
Whale season generally runs between May and November each year and construction of the new causeway - which will include pile driving - is expected to run across at least one whale season.
Whale expert Dr Claire Charlton (Curtin University) and chief scientist, Encounter Bay Right Whale Study said Encounter Bay, inclusive of Victor Harbor and Granite Island is a "critical habitat for the endangered southern right whale and is recognised nationally as a biologically important area for nursing, breeding and migration between May and November".
"Underwater noise is a key threat to marine mammals. The underwater noise generated from the proposed pile driving for the causeway development will impact the whales in the area," Dr Charlton said.
"Pile driving activities produce sound levels that are known to cause behavioural disturbance and potential physical impact to whales, particularly during sensitive life stages with newborn calves.
"It is our duty to provide protection and safety to these endangered whales to ensure that they continue to return to Encounter Bay."
Dr Charlton said proposed construction time-frames were concerning given that the area surrounding Granite Island was considered "a critical nursery ground for endangered whales that reside in the shallow protected waters of the bay for months at a time to rear their young".
"Best practice management would include avoidance of pile driving activities during whale season in a critical nursery area," she said.
Construction works are due to begin early this year, with McConnell Dowell Constructors (Aust) Pty Ltd being the successful company as part of the Early Contractor Involvement process for the $31.1 million project, which is being delivered by the Department of Infrastructure and Transport (DIT).
The causeway project is currently before the State Planning Commission, with public consultation open until midnight Friday, January 22.
As part of DIT's application to the State Planning Commission, an Environment and Heritage Report addresses the potential impacts of the project on marine life including southern right whales and sets out mitigation and management measures.
"Potential impacts to fauna are largely associated with the construction of the new causeway and decommissioning of the existing causeway and are considered to be short term and localised," the report reads.
"Noise impacts on marine mammals will be managed consistent with the Department for Infrastructure and Transport Underwater Piling Noise Guidelines. This includes use of an observation zone and exclusion zone and a spotter along with provision for soft starts.
"In addition, it is expected that noise reduction of 10 decibels or more will be achieved through use of a modified piling gate..."
The report acknowledges the presence of whales in the area surrounding the causeway and states: "underwater noise from piling activity can potentially impact the southern right whale through threshold shift or behavioural impacts".
As part of its application, DIT has proposed an exclusion zone of 300 metres radius, where piling works will cease if a whale/s enters the zone.
This is considered to "provide a conservative approach as at this distance, the criteria to avoid both physiological and behavioural impacts will be achieved", according to DIT.
However, these measures do not go far enough according to Dr Fredrik Christiansen, assistant professor and marine biologist (Murdoch University, WA, and Aarhus University, Denmark), who specialises in southern right whale behaviour and physiology.
Dr Christiansen said the noise produced by pile driving and construction operations during the Granite Island Causeway project would negatively influence southern right whales coming to Encounter Bay and suggested construction works should take place outside of whale season.
"The chance that mother-calf pairs in particular will be negatively affected regarding their nursing behaviour and/or reduced amount of energy available for the calf, is significant," Dr Christainsen said.
"Studies conducted at the Head of Bight in South Australia show that southern right whale calves need to gain considerable energy from their mothers in order to grow to a sufficient size to migrate back to their feeding grounds.
"Further, southern right whale mothers are fasting during their time in Australian waters, which means that they have a finite amount of energy that they can supply to their calves through milk production. Hence, any disturbance on the behaviour of the mothers that could increase their energy expenditure will result in a reduction of energy available for their calf and for their return migration."
Spokesperson for local conservation group Encounter Whales Elizabeth Steele-Collins, said the group was not opposed to the causeway project but was "strongly opposed to any construction work taking place during whale season".
"The purpose of the causeway project is to preserve the Horse Drawn Tram and assure ongoing public access to Granite Island, both valuable tourist attractions. However, the whales are the greatest winter tourist attraction for the area and the proposal to construct the new causeway with the resultant underwater noise, during whale season puts this at risk," Ms Steele-Collins said.
"The noise generated by pile driving and construction works will be considerable. Sound travels at 1.5 km per second underwater, much faster than in air, and is much more intense.
"This noise will be heard by the whales many kilometres away as they approach on their migration corridors.
"Many of the proposed mitigation strategies for minimising the effect of construction noise on the whales are either inadequate or inappropriate for a federally recognised Biologically Important Area like Encounter Bay, which contains a whale breeding and nursery area.
"The threat from the Granite Island Causeway construction will only exacerbate the issues migrating southern right whales already face with increased boating activity and its associated incidental noise, illegal approach, and potential collision.
"It doesn't make sense to do this [causeway construction] in whale season with so much at stake, both economically and environmentally. It just seems a no-brainer."
McConnell Dowell Constructors and DIT have been contacted for comment.
McConnell Dowell Constructors' website states environmental commitments are "a central concern in all areas of our business."
"Environmental management is everybody's responsibility, on every job, regardless of role, or the nature or location of the project and we have been recognised throughout our industry for our collaborative, rigorous approach to environmental standards," the statement reads.
Public consultation on DIT's Development Application currently before the State Planning Commission closes at midnight, Friday January 22 and can be accessed via: plan.sa.gov.au/have_your_say/notified_developments/state_developments?fbclid=IwAR2LKuapgeNA06b1PAtXhHP6ARhCefkaSyB4VI82AnqiSuzmzHXu8knoDEk
The relevant Development Number to access documents and provide feedback is: 453/V010/20.