According to the PMBOK Guide, 6th edition, Section 11.2.1.2, Assumptions Log, an assumption is a factor that is considered to be true, real, or certain without proof or demonstration. Assumptions can affect the project planning and execution, and should be identified, documented, validated, and updated throughout the project life cycle. The assumptions log is an output of the Identify Risks process, and it records the project assumptions and their potential impact, validity, and priority. If the assumptions are found to be invalid or inaccurate, they may introduce new risks or change the existing risk exposure. Therefore, the project manager should update the assumptions log and assess the risk associated with the conflicting infrastructure pieces, and plan appropriate risk responses if needed. References: PMBOK Guide, 6th edition, Section 11.2.1.2, Assumptions Log When conflicting infrastructure pieces are identified, the project manager should update the assumptions log to reflect the new information and assess the risks associated with the conflicting pieces. This allows the project manager to make informed decisions about how to address potential issues and avoid future problems.
(Reference: Project Management Institute. A Guide to the Project Management Body of Knowledge (PMBOK Guide) - Sixth Edition, Section 11.3)