It will make room for an extra 4 million tonnes of garbage.

A council report said the highest point of the tip extension would be 110 metres above sea level, compared with 83 metres now. The top of the tip above 90 metres high would be visible from Rathmines and Buttaba and residents at Awaba would see it at a height of 80 metres.

The report said "daily cover of the landfill face" would remove lighter colours and reduce its "visual impact".

A preliminary environmental assessment for the plan has been lodged with the Department of Planning.

The extension is needed because the tip, commissioned in 1986 and extended in 1995, is planned to be full in four to six years.

The report said it did not intend to extend the tip to accept more waste each year, but to prolong the tip's lifespan while developing "waste-minimisation practices".

It said the tip received 100,000 tonnes of waste a year, which was expected to increase by 1.2 per cent to 1.3 per cent a year.

There was a "high possibility" that excavating land for the tip extension would effect groundwater, the report said.