Dams and reservoirs are often partially justified on the basis of an intangible benefit related to the property value changes that they allegedly induce. This assumption is tested by using the G. Ross Lord Dam and parkland on the west Don River in Toronto. The project had virtually no impact on residential property values in the summer of 1972 while the dam was under construction. The magnitude of the social benefit related to the residential land value changes induced by such a project is considered.