Exchanging ballast water at sea
Safe Seas Clean Seas Issue 52, August 2017
About 20 NZ-flagged commercial ships will be affected by the change in our maritime laws, along with a few New Zealand ocean-going yachts that may carry ballast. Examples of commercial vessels that may be affected include large fishing vessels operating in other countries and inter-island ferries travelling overseas to dry-dock for maintenance.
New Zealand acceded to the International Maritime Organisation’s Ballast Water Management Convention last year, with its provisions coming into force from September 8.
International vessels travelling to this country, such as those carrying cargo and cruise passengers, are expected to already comply with the convention as required by overseas jurisdictions and existing Ministry of Primary Industries’ regulations.
Maritime NZ Principal Technical Adviser Paul Vorwerk says that from next month New Zealand will require all vessels to manage their ballast water either through exchange of ballast 200 nautical miles out to sea – or through the use of treatment equipment to clean ballast water, if discharging without exchange.
“There are various survey, certification and document requirements, but these vary depending on the size of the vessels concerned. For example, vessels of 400 gross tonnes or more will need to hold an International Ballast Water Management Certificate, while vessels less than 400 gross tonnes will be required to apply for a Ballast Water Management Approval from Maritime NZ.”
Paul says the main purpose of the Convention is to manage and control the risk posed by biological materials going out from, and coming into, New Zealand waters. This is why the requirements relate to ships travelling internationally. Ballast water discharge typically contains a variety of biological materials, which often include non-native, nuisance, exotic species that can cause ecological and economic damage.
In the past ships on international voyages often took on-board ballast in the coastal waters of one country, after discharging wastewater or unloading cargo, and then discharged at the next port of call when loading more cargo.
While initially the requirements of the Convention are mostly managed by exchanging ballast water mid-ocean, the intention is that ship owners will eventually need to install ballast water treatment equipment. Such systems are now generally included in the design and construction of large new-builds.