French scientists, who are in New Caledonia to present their findings on the environmental effects of the Goro Nickel project, have expressed concern over the impact the plant's waste may have on the environment.
The scientists say the manganese content in the waste should not exceed 10 mg per litre, as opposed to the current 100 mg per litre.
They also stress concentrations of cobalt and chrome should be checked regularly.
One of the main project opponents is the Kanak activist group, Rheebu Nuu.
Its representative, Jacques Boengkih, says many questions about the manganese waste remain unanswered.
"Nobody has been asking where the ninety microgramme will go. It is strange that this question was not raised by the scientists. The only new thing we have heard is that the scientists said one should be careful where this waste will be dumped. 15"
Goro Nickel says it has already reduced its manganese content in the marine affluent to twenty milligrams per litre, but its technicians are looking into the matter.