The way people participate in decision making has radically changed over the last few decades. Technology has facilitated the sharing of knowledge, ideas and opinions across social structures and, has allowed grass-root initiatives to flourish. Participatory civic technology has helped local communities to embrace civic action on matters of shared concern. In this case study, we describe SENSEI, a year-long participatory sensing movement. Local community organisations, decision makers, families, individuals and researchers worked together to co-create civic technologies to help them address environmental issues of shared interest, such as invasive plant species, abandoned items in the forests and nice places. Over 240 local participants have taken part to the different stages of this year long process which included ten community events and workshops. As a result, over hundred concrete ideas about issues of common interest were generated, nearly thirty civic tech prototypes were designed and developed, along hundreds of environmental observations. In this paper, we describe the process or orchestration of this initiative and present key reflections from it.