The article says that it was known at the time to be likely to be within a 2000m^2 block, narrowing beyond that will be harder since the rubbish is distributed

The article says that it was known at the time to be likely to be within a 2000m^2 block, narrowing beyond that will be harder since the rubbish is distributed across it (bulldozers keeping it somewhat level as dumping proceeds, rather than keeping it date-sorted). At the time that he first understood his loss the prospective value was $7.5 million: far from negligible but not a slam-dunk proposition for sifting through 10,000 tonnes of mixed bulk waste while continuing to operate the landfill.