A group of independent European scientists has completed its latest visit to New Caledonia to assess the Goro Nickel project in the territory's south.
One of the scientists, Jean-Charles Massabiau, says the manganese content in the pipeline discharge into the lagoon has been reduced.
He says Goro Nickel is now looking at reducing it by up to 80 percent to 20 milligrammes per litre.
But he says this is still way in excess of the 1 milligramme per litre demanded by the Kanak Rheebu Nuu environmentalist group.
The scientists will issue their final report in two months after which a so-called ICPE operating licence can be considered to be issued for Goro to operate.
The last ICPE licence was annulled by a Noumea court this year but Goro Nickel has continued building its two-billion US dollar plant.
Rheebu Nuu still demands a halt to the construction until environmental concerns have been dealt with.