Irish Water says it is working towards submitting a planning application in 2019 for wastewater infrastructure for the towns of Rathmullan, Milford and Ramelton.
The water company plans to build treatment stations to ensure treated effluent is discharged into the Leannon Estuary.
At present, wastewater treatment is non-existent in Ramelton and Rathmullan and substandard in Milford. The three towns are discharging untreated or partially treated wastewater into the environment.
Ending this practice, according to Irish Water, will be achieved through the construction of pumping stations at the three locations, rising mains and a combined wastewater treatment plant.
The environmental studies required to support the planning application for these works are ongoing.
It is envisaged that planning, design and construction will take approximately 3 to 4 years and will be undertaken between 2018 and 2021.