Rarotonga and Aitutaki Waste Management Project. "Sewage Treatment Pond Facility"

Re your request for advice and comments: Although there is little detail shown in the EIA regarding the Sewage Treatment Ponds, it is noted from the drawings and script that the proposed system does not appear to have any denitrification or nutrient removal facility. The omission of nutrient and particularly nitrogen removal from the plant outflow can have serious environmental and economic consequences. There is considerable data available on this subject and I have listed the history of some of it below.

In 1976, At the request of the Cook Islands Government the South Pacific Commission commissioned Arthur Dahl, a marine biologist specialising in coral reef systems, to undertake a marine survey of the lagoons of Rarotonga and Aitutaki.

In his report, and at various meetings, he alerted the Cook Islands Government and the general community to the serious lagoon degradation that could be expected in the future from "nutrients", particularly "nitrogen" and nitrates, coming from septic tanks and sewage systems. These nutrients he said, would enter the underground fresh water lens and be discharged into the lagoon. He described how the degradation would start, how it would progress, and what would happen as a result.

For the last 27 years I have been watching exactly what Dahl foretold then, happening.

In 1980, Professor Kirk, the head of Geography and Coastal Research from the University of Canterbury carried out a lagoon study on Rarotonga, confirmed the findings of Arthur Dahl, and during a talk to Cabinet on the subject, stressed the dangers we could expect to the lagoons from sewage-sourced "nutrients", particularly "nitrogen".

In 1990, Elliot Norse, Chief Scientist of the United States Centre for Marine Conservation, at a World Conference in Australia, blamed the death of coral in many countries on poor sewage disposal systems, and "nutrients". 'The nutrients encourage algae growth, take over reefs and kill the coral. This is happening all over the world,' he said. Extracts from his speech were reported in the Cook Islands News in December 1990.

In 1994, the Asian Development Bank sent a team of consultants, the Barrett Consulting Group, to Rarotonga to investigate a waste management and sewage system. The sewage specialist, Frank Zaletel, was aware there could be a potential nitrate problem and produced a model to identify these issues. He noted that the outflow from septic tanks and all other treatment plants at the time discharged their nutrient laden liquids into the ground water, which then carried it into the lagoon.

He also recorded that the resulting flow of nutrients, particularly nitrates, has been one of the major problems of lagoon environmental deterioration to date.

In November 1994, Zaletel held a meeting with the Cook Islands "Management Implementation Committee" and explained the dangers of nitrates in tropical lagoons in some detail. He also advised that if the nitrate problem was not addressed then significant algal blooms in the coastal reef lagoons could occur (as we well know, this has now happened) and disclosed alternative plans that in the event a Central Sewage Reticulation System was not feasible to be put in place, then all individual household septic tanks should be upgraded with denitrification capability.

All large sewage treatment plants (like hotels) should also be upgraded to include denitrification.

Fourteen members of the Management Committee attended the Nov meeting which include members from: Conservation Dept, Survey Dept, Dept of Water supply, Development planning, Economic Planning, General Licensing Authority, Health Dept, Ministry of Works, Special Projects Division and the Chamber of Commerce.

In 1997 It was reported that research at the "Waquoit Bay National Estuarine Research Centre" (USA) showed that nitrogen was the critical nutrient in marine systems. At this time numerous reports were also coming from Australia (Great Barrier Reef Marine Park Authority, and Australian Institute of Marine Science) and Hawai'i, warning of the dangers of nitrates entering tropical coral lagoon systems.

In 2000 the US National Research Council Report talked about: Cleaning Coastal Waters: Understanding and Reducing Nutrient Pollution, and said: 'Monitoring efforts must move beyond faecal coliform counts and dissolved oxygen' and 'routinely and consistently monitor for dissolved nitrogen and phosphorus.

In 2002, SOPAC's director, Alfred Simpson, when presenting SOPAC's 31st annual meeting said : 'The greatest threat to the marine environment is from land based pollution and the greatest of these is sewage. What insurance do we carry against the destruction of our reefs and coastal environment?'

In 2002, Dr Dan Walker, National Academy of Sciences, in an editorial titled "Addressing Coastal Pollution": "Let's Get It Right", talked about beach closings, harmful algal blooms, well documented "dead zones" and major threats to coastal environmental quality. He said: 'As with efforts to monitor (and control) the nitrogen and phosphorus responsible for nutrient over-enrichment of coastal waters, it will be just as important to measure (and control) the concentrations in rivers and streams entering these coastal waters.'

Since Cook Islands Government personnel have been constantly informed on this issue for so many years, the question must be: Why on earth are we now going into major projects, on two tourist dependent islands, which will apparently discharge a large concentration of enhanced lagoon-killing sewage nutrients, and specially nitrates, into the groundwater that continually flows into the lagoon?

I do not blame Meritec Consultants for this oversight because it is most likely they were not informed of this problem. However, the Brockman Tym International consultancy which prepared the base report in February 2000 is a different story, because they were told, but apparently did not understand the significance, did not research it, and chose to ignore it.

An interchange of views on an international wastewater Internet site recently is appropriate:-

Azam Khan wrote: 'I am looking for information regarding nitrogen values in seawater for the protection of marine species. We are assessing the discharge of sewage-sourced nitrogen into a coastal area. The current method of treatment and discharge is natural seepage in the foreshore area.'

David Venhuizen, a leading wastewater engineer from Texas well versed with the nitrogen/nitrate problem in marine areas, started his answer with: 'What is "treatment by natural seepage in the foreshore area"? Is this like a septic tank drain-field on the beach?'

Don't laugh, because that is exactly what we are doing here.

It should be clearly understood that one of the results of destruction of life in a coral lagoon is a drop in sand production. This in turn causes coastal beach erosion.

What do you think is one of the main reasons we have been experiencing such widespread coastal erosion and loss of beaches over the last few years? Isn't this exactly what the coastal researchers, one after another, have been saying would happen? For the last 27 years? Statistical reports indicate that over 95 per cent of tourist visitors state they wish to spend time on our beaches. What do you think will happen to the tourist industry and the country's economy when the beaches are finally polluted out of existence? Just because other countries have destroyed their beaches, and their economies doesn't mean we have to.

In this respect, the competency of the Environment Service should be under scrutiny for allowing this project to advance as far as it has in its present form. There is no mention anywhere in the EIA of denitrification or nutrient treatment, but it is mentioned that the normal sewage nutrients will be compounded by the addition of significant quantities of nitrogen nutrients from excess landfill leachate.

The Environment Service should have queried this plan immediately and allowed time for alteration to the design without causing further delays to the project. There is no excuse for not doing so. This subject has been a major environmental agenda item for years. It is in the 1989 SPREP EIA Manual.

Since there is a groundwater lens encircling both the islands of Rarotonga and Aitutaki, which ultimately finishes up flowing into the lagoon, any proposed sewage treatment plant anywhere should be designed with some form of nutrient removal, (there are several methods) with denitrification as a minimum.

This was the intention of the original ADB planning but it got sidetracked, and it seems no-one picked it up. For very good, both environmental and economic reasons, it should be reinstated. We only have one chance at this. As Dr Walker of NAS said earlier: 'Let's get it right'.

Don Dorrell
Managing Director, Coastal Environmental International Ltd.