The successful delivery of large complex infrastructure projects continues to challenge the civil engineering profession, with a predominance of projects delivered late and over budget. Many researchers have investigated methods and means of improving the less-than-satisfactory record of the execution of these projects. One recent research direction suggests that improvements in project delivery may not be realized until the project setting is understood from the as-lived perspective of the participants. Following this direction, the research described in this dissertation explores the personal and interpersonal dynamics operating within projects, treating them as complex social processes. The social dimensions explored in this study involve team leaders and staff engineers in a matriced organization handling a large urban design-build infrastructure project. The interactions among the participants within and across units and levels had both positive and negative impacts. The data for this exploratory case study comes from semi-structured interviews and online surveys collected at three points over eleven months when the project was in the design phase. Interviews were conducted with a limited number of individuals; the survey was collected from the larger engineering organization. From the interview data, issues which impacted project delivery were identified as the relationship with supervision, the availability of information, an understanding of the larger project context, and the response to project constraints. The survey data was used primarily to understand the social dimensions affecting two engineering disciplines, one that performed well and one that performed poorly. Issues that aligned with the performance differences included frequency of contact with supervision, the ability to make decisions, and effective use of time available to complete design tasks. Data from the two modes of investigation demonstrated strong triangulation. Recommendations for both academia and industry are provided. / Ph. D.