HALIFAX -- The Nova Scotia government is moving ahead with plans to clean up one of most polluted corners of the province.

Last year, the province's Liberal government promised to close the Boat Harbour effluent treatment facility in Pictou County by January 2020, and eventually transform the filthy waterway into a clean, tidal estuary.

The government issued a request for proposals Monday, saying it wants an engineering firm to design a major remediation effort that will return Boat Harbour to its natural state.

A meeting with bidders and a site visit is scheduled for Dec. 14 at the Pictou Landing Fire Hall, and the deadline for submissions is Feb. 3.

When the provincial government tabled legislation to require the cleanup in April 2015, it set aside $52.3 million for the initial stages of the project.

The Pictou Landing First Nation has long alleged that effluent from a nearby pulp mill has polluted the harbour.

When the legislation for the cleanup was tabled, chief Andrea Paul said it marked an important milestone for the First Nation.

The bill stemmed from an agreement reached in June 2014 after the First Nation ended a blockade that started when a leak was found in a pipe carrying wastewater from the nearby Northern Pulp mill to the treatment facility.

Northern Pulp was later fined $225,000 under the Federal Fisheries Act. A provincial court judge concluded the leak included 47 million litres of "toxic" effluent.

Government officials have said risk assessments were needed to determine whether the contaminants in the harbour will be destroyed or sent to a secure landfill site.