A conservative analysis of the potential health impacts of a proposed wastewater pipeline into the Pacific Ocean off South Canterbury has found they would be less than minor, a hearings panel was told on Tuesday.

The effects of the discharge on human health (from Oceania Dairys proposed 7.5km wastewater pipe at Glenavy) are predicted to be less than minor, particularly given the conservative nature of the risk assessment, Dr Helen Rebecca Stott, an environmental scientist with the National Institute of Water and Atmospheric Research Limited said.

The advanced wastewater treatment proposed, using UV disinfection, will improve the current microbiology quality of dairy processing wastewater to further reduce potential health risk from wastewaters discharged, Stott told the Environment Canterbury hearing being held in Waimate.

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Stott has more than 20 years experience in environmental research and consultancy focussing on wastewater treatment, water quality and health.

My experience with dairy factories is that typically the wastewater treatment plant is only a dissolved air flotation plant but the wastewater treatment being proposed, particularly with UV disinfection, is an advanced kind of treatment being proposed by Oceania.

Typically, UV disinfection is a very good tertiary treatment in deactivating microbial contaminants, particularly microbial pathogens.

Stott said her quantative microbial risk assessment into the proposed pipelines effect on recreational water users was based on the current system without UV filtration and therefore considered conservative.

My risk assessment included modelling that used information from the predicted wastewater dilution from the shore, microbial pathogens detected in the Oceania processing wastewater and other model input variables including the intensity and duration of exposure.

She found that concentrations of three bacterial pathogens detected in the wastewater (Campylobacter, Listeria and Staphylococcus aureus) were unlikely to exceed the dose required to have a 1 per cent risk of infection after dilution in the surrounding environment.

Stott assessed the impact to humans through direct contact, ingestion and inhalation, such as from sea spray on the beach, despite recommendations that very little recreation activity occurs there.

Panel chairman Paul Rogers asked Stott how her analysis would change if the advised level of recreational activity was wrong, or were to change in the future.

Whenever you undertake a human health assessment we always take a precautionary approach and assume somebody could be walking along that coastline so that is the nature of the risk assessment.

The only differences might be if people were in a more immediate vicinity of that wastewater discharge at the output site, however, within my modelling I have taken a conservative approach in that I have not considered any deactivation of pathogens in the marine environment.

John Bisset/Stuff

Commissioner Hoani Langsbury asked why anglers and landowners against the proposal had not been questioned as part of the research into recreational use of the area.

She also eliminated the impact of sunlight in deactivating pathogens that come to the surface, she said.

The limited recreational use of the coast at the proposed site of the pipeline was presented by Rob Greenaway, an accredited recreation professional with Recreation Aotearoa.

The critical thing is the outfall location is in an area thats midway between two significant recreational areas the Waitaki River mouth and, further north, the Waihao River mouth, he said.

The site is 7.5 kilometres north of the Waitaki River and 11km south of Waihao, so the ability to have an impact on either of those sites is very limited.

He noted some recreational use was made of Morgans Beach Road, which has a picnic area and is used by some anglers and quadbikers, but said youd be very brave to swim in the waters along the coast because of dumping waves and the lack of lifeguards.

Having spoken to three anglers, he argued they were unlikely to travel to the beach at Archibald Rd, the proposed site for the pipeline, where fishing is not as good as at the river mouths and access is significantly harder, requiring travel along an unformed road and a scramble down to the beach.

When questioned by commissioner Hoani Langsbury about his interviews, Greenaway conceded he had not spoken to the anglers who had submitted against the proposal, or the landowners along the coast.

He agreed with the panel that landowners may be more likely to fish there due to convenience.

supplied

Map of the coastline where Oceania Dairy proposes to construct its wastewater pipe, including all beach access points.

Langsbury asked whether access to the coast at Archibald Rd would be improved by the construction of the pipeline and would entice more people, but Greenaway did not think that would be the case because there is still little appeal to the site over others along the coast.

He said there were good reasons that a recreation setting had not been developed there.

It would be a lot of work to create and it would be a lot of work to maintain it. I would be very, very surprised if there was any demand, to be honest, for recreation at Archibald Rd.

Panel member Emma Christmas asked whether recreational use may be further reduced if it were to become a discharge site.

The real effects, the potential health effects, are negligible so that is a good starting point, Greenaway said.

There can be perceptional issues, clearly, and that depends on the angler.

Based on my experience people tend to go where there are fish.

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Health impacts of Oceania Dairy's pipeline 'less than minor', hearing told - Stuff.co.nz