It is operating at 9.7m and the consent would deepen it to 10.7m.
The port believed the extra depth would assist with improving safety margins for ship movements and provide greater capacity for vessels to take on additional cargo, a note to the NZX yesterday said.
The increased depth would be achieved by removing some higher areas that limit width and depth in the entrance channel.
Extensive consultation had been undertaken and the port had completed environmental assessments in preparation for lodging the consent, chairman Rex Chapman said.
"This is a major project for the port and will provide benefits to the region’s customers for years to come and aligns with the company’s purpose to facilitate the best logistic solutions for the region," he said.
Chief executive Nigel Gear said with uncertainty over the potential closure of New Zealand Aluminium Smelter by 2024, it was crucial the port continued to look for opportunities to secure growth and its future.
It was important Southland had a port with a competitive channel depth that would provide flexible options for shipping companies and new industry considering coming into the region.
"Covid-19 has also significantly impacted the world’s supply chains. An increase of depth in the harbour would assist in alleviating current congestion issues, as well as providing for growth in the future," he said.
It was expected the consent would be processed this calendar year and work could start within the next 24 months.
