D the G this bit should really be below the line. However. The idea of contaminated ground did not really kick off until the 90's. The science of determining severity of contamination and remediation is evolving by the day. There must be many brownfield sites redeveloped on top of a nightmare, escaping methane from landfill sites redeveloped as housing to name but one. I could name a few. As time goes by contaminated sites are subjected to far greater precision of investigation and more invasive procedures. As more is known, more has to be done, partly driven by legislation, partly by potential public liability concerns. As a result remediation costs also escalate. Could be making it a museum would make greater economic sense.
As a total aside I worked on an investigation for a sewer tunnel in stoke. We were happily drilling a hole in the street straight into coal workings a couple of meters down.
We has a positive reading for methane from the casing head and got out the gas board and coalboard. Both denied it was theirs. Anyway they had technicians putting a sniffer in the airbricks below the suspended floors of some adjacent houses. Ended up the police evacuated a good chunk of the street.
That made us really popular. We also had some holes to drill in a graveyard. With one we were chiseling on wood at two meters. We abandoned that one. We were in there for a couple of weeks and has to vanish everytime there was a funeral. I should really try and put some of the more entertaining moments in a book or songs.