It was 20 years ago that construction on top of a toxic dump was first considered, in 2001. Neither that or the original dumping of toxic waste 50 years ago should have ever been allowed.
Here in the Netherlands along with the cradle-to-cradle hype a paper reality has been created where all kinds of hazardous waste can be turned into 'building material' and then used (read: dumped) anywhere freely, and making double profits. There was a TV series last year, "De Vuilnisman" (the garbage man) that addressed various ways this happens.