A regional council spokeswoman said Pan Pac's reasoning for the extension was to further dilute effluent which was often visible.
Whirinaki residents had also become concerned about the visible effluent, she said.
The consent was granted on September 16 last year . But Maungaharuru Tangitu Trust has appealed the decision on grounds of cultural values. These values include the ability of the hapu to exercise kaitiakitanga and the effect on the environment's mauri, not just for Maori but for all.
They want alternatives to ocean discharge to be explored further and exhausted before the extension goes ahead.
Discussions are ongoing between the regional council, Pan Pac and Maungaharuru Tangitu Trust in an effort to reach a solution agreeable to all parties.
The treated pulp mill effluent would include sawmill effluent, water treatment plant effluent and landfill leachate with a maximum rate of discharge being 15,000 cubic metres per day.
Included in the consent was an expectation that the rate of discharge would not exceed 0.5 litres per second. There were several other measurement restrictions, including the average effluent temperature not exceeding 70C.
A clause in the resource consent states Pan Pac must report various figures about the effluent each month to the council. The effluent discharge must not cause oil or grease films, scums or foams, or floatable materials, conspicuous change in colour or visual clarity.
It must not emit odour, affect aquatic life, change the temperature of the water by more than 3C or the dissolved oxygen concentration to be less than 80 per cent, or undesirable biological growths.
The effluent discharge also means shellfish taken from the area would be unsafe to eat and Pan Pac was obliged to signpost that as well as undertake a mussel monitoring study at adjacent sites.
If the trust lost the appeal and the resource consent was to go ahead then Pan Pac would need to establish a Mana Whenua Kaitiaki Liaison Group with an agreed terms of reference contributed to by the trust, Petane Marae and any other appropriate mana whenua.
The liaison group's purpose is to promote shared understandings between mana whenua and the consent holder of their respective cultural, social and economic objectives and to develop a cultural monitoring programme.