Unsanitised dumpsites and leachate from landfills were among factors that contributed to serious pollution of rivers and the environment, he told reporters after visiting the 680ha sanitary landfill project located in the middle of an oil palm plantation, 50km from Kuala Lumpur, today.

"If we don't take preventive measures by creating landfills like this, then environmental and river pollution could only become worse," said Najib who is also chairman of the Cabinet Committee on Solid Waste Management.

The landfill is developed by KUB-Berjaya Enviro Sdn Bhd, a joint- venture company between KUB Malaysia Bhd and Berjaya Corporation Bhd. It can be filled wih 120 tonnes of garbage from Kuala Lumpur and Selangor for at least another 40 years.

Besides treating solid waste, it also has a treatment plant for leachate, whereby leachate is not released to the water system but to an area planted with greenery within the landfill.

Najib said the landfill project which had a 500-metre buffer zone was progressing well and of international standard.

Asked on the value of the landfill concession, he said: "We still have to sort this out because it is a matter of negotiation with the government. We hope to reach a decision on this soon."

On whether the government would give out more landfill concessions, he said the government were still considering some outstanding matters pertaining to capital expenditure on landfills.

However, he said, the standard for future landfills would be based on the standard of the Bukit Tagar landfill.

When asked on the progress of the closure of 16 open dumpsites announced by the government last year, he said they were in the process of being closed down and the government had appointed consultants to look into the matter.

Meanwhile, Minister of Natural Resources and Environment Datuk Seri Azmi Khalid, who accompanied Najib on the site visit, said the government decided to close only 16 out of more than 160 dumpsites in the country due to the high cost, about RM10 million per dumpsite.

It would also take about 10 years to treat the dumpsite including the leachate and other contaminants produced by the garbage, he added.