Mr Hosking said a 4000 square metre area was left exposed when a 21-lot subdivision was quashed when rubbish overflow from the Chisholm Street tip was found on the land.

The area was originally to have been a subdivision road and had been dug out to prepare for bitumen to a depth of 400 millimetres. 

However, Mr Hosking said the works undertaken took off the landfill’s “capping layer” instead.

“The area...is part of a water course and the water, instead of going over the top of the landfill, is going straight into it,” Mr Hosking said.

“Once in contact with decomposing solid waste, the water becomes contaminated.

“It then flows out of the waste material and is termed leachate.

“This additional leachate produces a wide range of other materials including methane, carbon dioxide and a complex mixture of organic acids, aldehydes and heavy metals.”

“This leachate is free to leave the waste and flow directly into the groundwater. 

“In other cases of this type, high concentration of leachate have been found in nearby springs and creeks.”

Mr Hosking also pointed to the 2014 auditor-general’s report into landfills which found: “Ballarat council has not adequately assessed or managed the legacy gas and leachate risks at their closed landfills”.

The Black Hill landfill operated between 1978 and 1982 but subsequent 2012 investigations found rubbish had overflown onto Duggan Street land.

Mr Hosking said few landfills built in the 1970s had environmental controls, including liners, and often received a wide range of waste materials.

Mr Hosking, who found 14,000 cubic tonnes of rubbish on his land during a private search by environmental firm Cardno Lane Piper, complained to the Environment Protection Authority.

The EPA has since given the council until November 30 to map the former landfill’s proper boundaries.

The council said it would continue to “work with the EPA following the receipt of the formal notice relating to the site”.