Community participation, an imperative ingredient in any intervention, in spite of all the recent emphasis, it has continued to remain a form of collective bargaining. Instead of reversing its position in face of community opposition, governments are tempted to reinforce it by seeking the scientific opinion from experts. By favouring this opinion as the rational approach, the government undermines the essence of community participation. To illustrate this point, the paper traces the recent history of M5 East Motorway Tunnel Exhaust Stock located in a residential area of Sydney. I show how, between two modes of knowledge systems of two groups opposing each other, a privileging process subordinates citizens' preferences and understandings to those held by experts. Thus the process of participation becomes circumscribed by the government's implicit preferences that are imposed on the community in the name of a more 'scientific' view irrespective of citizen opinions.