Managing the “receding edge”

Abstract

So much attention is paid to starting construction activities, and starting new work at regular time intervals to a beat (aka. takt) that-not surprisingly-work to finish those very activities may fall behind. This paper focuses, not on the start-, the “leading edge,”but on the end of activities, the “receding edge.” The receding edge articulates when work is “done-done” and the successor contractor may start their work, unimpeded by their predecessors' unfinished work or “leftovers” (e.g., areas left dirty and cluttered with remnants). This paper describes receding-edge activities related to forming, placing, and finishing post-tensioned, cast-in-place concrete slabs, observed on a project in San Francisco, California. The researchers went to the gemba, described the current situation, and exchanged ideas with the contractor on means to keep the receding edge progressing at the pace of the leading edge, that is: to improve the cycle time from start, to not just finished or “done,” but to “done-done” completion of each slab. Findings include the need to define standard processes (e.g., for clean-up work) as those observed appeared defective (one of Ohno's 7 wastes) or none existed, and to designate resources to accomplish them. This paper contributes to knowledge by articulating the receding edge concept, describing challenges in managing it, and documenting lean methods as countermeasures to those challenges. When managed considering the production impact of receding-edge work on the contractor responsible for it and on follow-on contractors, the case for cycle time reduction is easy to make and worth the money.