Background: Environmental sustainability-focused service-learning programs can aid communities in addressing environmental problems and provide students with hands-on training. Understanding the implementation of such programs can inform research and application. Purpose: We investigate the implementation of an environmental sustainability-focused service-learning program (E-Corps) at a large New England public university. Our inquiry sought to better understand epistemic communities by addressing the research question: What conditions, including contextual factors and resources (i.e., funding, university context) and people (i.e., faculty, their orientation to teaching, how they work together), supported the establishment of an epistemic community in the implementation of E-Corps? Methodology/Approach: We employ frameworks of 1) Design Based Implementation Research (DBIR), which considers problems from multiple stakeholders' perspectives, collaborative design, pedagogical theory and knowledge, and capacity for sustaining change, and 2) epistemic communities-the stakeholders recursively generating, using, and refining pedagogical knowledge. We thematically analyzed interviews with students (n=7), two rounds of interviews with faculty (n=7), and participant observations of four E-Corps team meetings (n=13). Findings/Conclusions: Findings show that epistemic community within E-Corps' implementation was supported by 1) an existing context of resources within the university, and 2) a robust university-partnership prioritizing community benefits with aligned instructor approaches. Our work informs both research on DBIR and epistemic communities as well as the practical implementation of university-community environmental partnerships.