Citizen participation in the planning and development of public water supply infrastructure improvements in becoming increasingly important, particularly as a mechanism to establish public support for a project. Without favorable public support for a capital investment, a public water supplier may not obtain the necessary permits and other approvals or procure the funding necessary to construct the project, regardless of its technical merits and need. In today's climate of social and political activism, fueled in part by the public's skepticism of government and public agencies, people demand more services and greater responsiveness from their public water providers yet also seem to trust less the provider's technical expertise and professional judgement. Effective public participation programs that engage affected communities and constituencies in the planning and development of a public water supply capital improvement temper the public's skepticism and have become an integral component to the successful completion of a project. This paper highlights case studies from three working groups and examines how the groups have operated and participated in the development of the MetroWest Tunnel. Each case study reinforces the need for public support for and participation in the development of public water supply infrastructure improvements. These case studies can be beneficial to other water utilities and government agencies initiating a public participation program for a significant infrastructure improvement project.