The Tamar River will be cleaned up if promised upgrades to major infrastructure and catchment projects along the estuary and upstream go ahead.
Prime Minister Malcolm Turnbull will announce the $94.6 million fix in Launceston on Friday, which will need to be jointly funded by the state and federal governments.
It comes after a report from the Tamar Estuary Management Taskforce, released on Thursday, made 12 project recommendations to clean up the river.
The taskforce was established under the Launceston City Deal framework.
The recommendations included $10 million worth of “catchment actions” across dairy, grazing and urban areas, and $84.6 million worth of “priority projects” within the combined system.
The catchment actions would seek to exclude stock from streams, rehabilitate vegetation buffers on grazing properties, ensure better effluent management on dairy farms, and remove sewage intrusion into the separated stormwater system in Launceston, the report said.
That was expected to reduce pathogen concentrations in the Launceston to Legana zone by more than 4 per cent.
The combined system actions included improved pumping rates and transmission capacity to take greater volumes of combined system flows to the Ti Tree Bend sewage treatment plant, implementing a series of offline storages to capture the “first flush” of combined system sewage, and diverting separated sewage catchments straight to Ti Tree Bend.
Those projects were expected to reduce pathogen concentrations in the Launceston to Legana zone by 35 per cent.
Mr Turnbull said the federal government would partner with a re-elected Liberal state government to complete the comprehensive list of actions identified by the taskforce.
“The partnership will enable 12 projects to be undertaken along the Tamar Estuary… and will receive equal funding from the state and Commonwealth,” he said.
Premier Will Hodgman said work would be undertaken over a period of five years from 2019.