Plans to reduce the environmental legacy of Norfolk's disused landfill sites – and to maximise income from methane gas generated – will be discussed by councillors at a meeting this morning (Tuesday).

A report to the county council's environment overview and scrutiny panel outlines the effectiveness of work to prevent gas and groundwater pollutants from escaping.

It shows that since the county council took over responsibility for six permitted sites in February 2008, leachate levels at all of them have been brought into compliance with regulatory standards.

Meanwhile, advanced monitoring and engineering solutions have reduced the cost of managing leachate from �590,523 in 2008/09 to �159,692 in 2010/11.

In particular, the report details the work being done at five closed landfill sites – Mayton Wood, Costessey, Snetterton, Bergh Apton and Morningthorpe – to minimise environmental impacts and increase income from gas.

Predicted income from gas produced at the sites is �280,000 in 2011/12, accounting for 22pc of their total management costs.

But this income is expected to reduce by 10pc each year as the waste degrades, and officers are looking at ways to offset this decline.

In July, the council submitted a joint bid for EU funding with the Environment Agency to cover 50pc of the cost of a project to find new ways of assessing and capturing methane from older sites where the quality and quantity of gas is normally considered uneconomic to extract.

Bill Borrett, Norfolk's cabinet member for environment and waste said: 'This report clearly demonstrates that Norfolk County Council is successfully meeting its legal and moral responsibilities to protect people and the environment from the legacy of dumping our waste in landfill sites over many, many years.

'It also shows that we have a first class environmental management approach. While this costs in the region of �2m each year, we are clearly taking advantage of as many opportunities as possible to offset this, for example by turning methane into a useful resource – energy.'

Mr Borrett said the council's obligations would not reduce in the short to medium term, given that Norfolk currently still uses landfill as its primary waste disposal solution.

'Today, our waste management policy is concentrate on doing as much as possible to help boost Norfolk's recycling rates and drive down the amount of rubbish sent to landfill,' he said. 'With the potential for modern waste treatment technology to deal with the rubbish that's left over, the future of landfill – and its potential risk to human health and the environment, plus the huge financial cost of landfill tax which will cost us �13m this year – will steadily decline.'

The report says at Mayton Wood landfill, between Coltishall and Buxton, 'historical' levels of groundwater contamination are not declining as expected, so monitoring officers are planning a further review next year.

At Costessey landfill outside Norwich, which closed in 2007 after accepting 2,100,000 tonnes of waste, a long-standing issue of 'gas migration' along the eastern boundary continues despite continued remedial efforts.

The next steps to resolve the problem include upgrading drainage, multilevel well screening, improved leachate control and repairs to poorly-decommissioned gas wells.

Morningthorpe landfill's contamination levels in the groundwater near Long Stratton are 'slowly but consistently rising'. No quality standards have yet been exceeded, but officers are investigating the cause of the trend.

The report says that the cold winter of 2010/11 resulted in leachate management systems freezing, pushing Costessey and Mayton Wood out of compliance for four months – although both sites are now back within regulatory limits.