Water vapor is co-distilled with water vapor in room temperature evaporation. Humid air a 70F has a partial pressure of about 0.2 PSI - a substantial amount. I would have to look into tabular data on the H2O TCE system to see, but it is substantial = the smell you get. It also has it's own presence on dry air, but it is higher if water present due to low temperature co-distillation. These soils need to be dug up -washed with super-critical CO2 ($$$), then baked dry with the vapor condensed. This has been done in Toronto at a few old factories. Later they started to create a large underwater landfill area - the 'spit' and created a number of clay and membrane lined lagoons(embayments) where they buried it and covered it with clean fill to make a wild life area. Started about 50-75 years ago and it was well built and monitored since then and has stayed sealed.https://en.wikipedia.org/wiki/Leslie_Street_Spit