The environmental search checks if any near neighbour has permission to store chemicals, store or dispose of rubbish (licensed tip), has permission to extract water from a borehole, or permission to dispose of effluent into a watercourse - that sort of thing. I'm not convinced its worthwhile in a residential area because if one has one's wits about one, you'd have done such a tour around the immediate area anyway. If its a mixed area, with some light industrial premises, its maybe worth having.