Make field recordings on the site. Amplify that which is unheard to the naked ear. Is there water? Utilise waterproof microphones. Record animal sounds, traffic sounds, the sounds of the distant city...
Use contact microphones to create an audio portrait of the textures on the wasteland.
Weave together sounds to create a collage.
Perhaps mix in interviews conducted on/about the site.
And why not song, too? Think of Ewan MacColl, Peggy Seeger and Charles Parkers' Radio Ballads.