Environment minister Randy Delorey said Thursday seven of the eight changes to the permit, which was first issued to the mill in April, are administrative and mostly deal with wording.
The eighth relates to reductions in water input usage, and is being returned to the department for further assessment.
Delorey said the decision depends on whether it is possible for the mill to reduce its water use by the amount requested in the approval.
"They've questioned the technical feasibility of achieving those targets," Delorey said of Northern Pulp.
Delorey said department staff set the targets based on the information available at the time the original approval was issued. He said mill officials provided new information to him during the appeal process, which he couldn't share.
"It wouldn't be appropriate for me to engage directly, while I'm making my decision, with technical staff," he said. "So to ensure the integrity of the appeal process, I haven't engaged staff to reassess that information...that's why the decision was to send it back."
Delorey emphasized the criteria for the approval is independent from legislation governing the mill's waste facility in Boat Harbour.
"Facilities like that get regulated under their own approvals," he said. "The industrial approval deals with the operating parameters of the mill itself."
But Delorey also alluded to what he called an interrelationship between water input and waste output.
"If there are changes to the water usage coming in, there may be impacts that are related," he said. "If a certain volume is coming in, you clearly can't have water going out that is greater than (that)."
Northern Pulp said in a statement that it is evaluating the long-term impact of the changes.