Prior work in engineering education has shown that individuals who do not identify with engineering groups, maintain a sense of belonging to, or perceive themselves as engineers are more likely to leave the profession. While significant research has been conducted on various internal, intimate (e.g., gender, race, sexuality, and religion) and external, social perspectives of identity (e.g., discourse, nature of engineering work, and content knowledge), little is known regarding the ways in which these identities intersect and evolve to form students' professional identities, particularly within a single engineering discipline. In this work in progress paper, we present the preliminary findings of the first phase of a quasi longitudinal grounded theory study consisting of 20 interviews with sophomore-, junior-, and senior-level undergraduate civil engineering students. By sharing our preliminary findings, we aim to describe and further establish the grounded theory methodology within engineering education research; engage engineering educators in a scholarly discussion regarding the value of this topic; and gain further insights for advancing this work.