PICTOU, N.S. -- The proposed route of a pipeline that would carry effluent from the Northern Pulp mill into the Northumberland Strait will be changed due to concerns over potential ice damage.

Kathy Cloutier, director of communications at Paper Excellence, said Tuesday a sonar study found ice scouring near the proposed location of the pipeline's outfall off Pictou, N.S.

She said that will mean the pipeline may have to go into deeper waters to avoid the ice that scrapes along the ocean bottom.

"You're doing this study to discover unknowns. Nobody would go into a project without full clarity on your proposed route," she said in a telephone interview.

"You're trying to avoid any impacts and have as clear a route as possible."

In addition, the undersea scans by Marine Geotech and Habitat Assessment in April, May and June found the proposed route was too close to a shipwreck discovered in July 2015 and a collapsed pier.

Cloutier said the new information means a delay in the company filing its environmental assessment report, and will lead to higher project costs.

Under provincial legislation, the mill has until Jan. 30, 2020, to replace its current wastewater treatment plant in Boat Harbour.

The wastewater lagoons contain nearly 50 years worth of toxic waste that provincial Environment Minister Iain Rankin has called one of the worst cases of environmental racism in the province.

It has been a major concern for the local Mi'kmaq community, which launched a lawsuit in 2010 seeking to eject the treatment plant from its land.

The proposal for a pipeline to transport the treated effluent from a new facility into the ocean has also met with opposition.

In February, groups representing fishermen in Nova Scotia, P.E.I., and New Brunswick suspended further meetings with the mill after voicing frustration over its insistence on a pipe.

The company has said it had thoroughly investigated the treatment options available to bleached kraft mills like Northern Pulp, which produce a higher quality paper.

It calls for a system that would meet all federal environmental standards for suspended solids and oxygen depletion.

Effluent would be carried by polyethelyne pipe across Pictou Harbour and released through six dispersal pipes into the Strait.

The company said the proposed system would reduce the need for bleaching chemicals by about 30 to 40 per cent.

Northern Pulp was originally to submit an environmental assessment to Nova Scotia's Environment Department sometime in July.

However, Cloutier said the latest sonar work means the environmental submission likely wouldn't be until the fall.

"This will mean winter construction," she said.

-- Story by Michael Tutton in Halifax.