Port on priority cleanup list

00:58, Aug 14 2014

A highly contaminated site at Port Nelson has been named as one the 10 areas in New Zealand which most urgently require a cleanup.

Calwell Slipway became contaminated after ships were washed and maintained there from the 1970s onwards.The main contaminant is tributyltin, formerly used in marine paints to reduce the growth of weed and other organisms on ship hulls.

Following international recognition of its serious effects on marine life, its use was stopped in the 1990s.

However, it is long-lasting in the marine environment and high concentrations are common around slipways, where hulls are routinely stripped and resurfaced.

Resource Management Act consents now require that vessels being serviced must be out of the water and fully "bunded" or surrounded by a containment wall before work begins. Washwater and debris from ship maintenance must be collected and disposed of appropriately.

Calwell Slipway is included in a list of 10 contaminated priority sites which the government named yesterday as part of a new initiative intended to help funding be allocated towards remediation in a more transparent way.


The area has been under stage three of its remediation since 2012, and is now approaching its final stage. Port Nelson infrastructure manager Matthew McDonald said the announcement did not herald any new stage or changes in the way the cleanup was being conducted.

"The contamination is historical, the issue is that sooner or later we're going to have to dredge it and we need somewhere to put the contaminated dredgings."

Previous remediation phases have focused on research and planning, and the project has cost $184,631 to date. The government has contributed $92,000 of this through the Ministry for the Environment, which is working with Port Nelson and Nelson City Council on the project. NCC does not contribute financially to the project but sends staff to assist.

McDonald said Port Nelson's preferred solution to the contamination was to refill the slipway with treated contaminated material, but it would cost "many millions".

"It is very expensive and therefore we're stepping back to review all our options as to how best to take it forward."

Port Nelson and NCC are discussing options for the remediation of the Calwell Slipway with the Ministry for the Environment.

The nine other contaminated priority sites are: Prohibition Mine, West Coast; Alexander Mine, West Coast; Kopeopeo Canal, Whakatane; Te Mome Stream, Lower Hutt; Miramar Gasworks, Wellington; Onehunga Aquifer, Auckland; Rotowaro Carbonisation Plan, Waikato; Masterton Gasworks, Wairarapa; Rudolf Steiner School, Christchurch.

The Nelson Mail