Direct Answer
Document field modifications by maintaining a field modification log that records: what changed (member ID, original condition, modified condition), when it changed, who authorized it (engineer's written approval), the cost impact, and whether the shop drawing needs to be revised to reflect the change. All engineer-authorized field modifications must be reflected in the as-built drawings.
Full Explanation
Field modifications to structural steel — burning an additional bolt hole, adding a field weld, flame-cutting a flange for clearance — must all be authorized in writing by the engineer of record. The documentation chain: (1) Field condition identified. (2) RFI submitted with proposed modification. (3) Engineer responds with written approval (often a sketch or redlined drawing). (4) Modification is performed by a qualified tradesman. (5) Modification is inspected and documented. (6) The shop drawing is revised to show the as-built condition, or a separate as-built sketch is created. (7) Field modification log entry made.
What This Means for Your Shop
Unauthorized field modifications are non-conformances. If discovered during final inspection, you may be required to restore the original condition — which is always more expensive than getting proper authorization first. 'Field engineering' (solving a fit-up problem yourself without the engineer) is a liability exposure.
Common Mistakes
Accepting verbal authorization from a field inspector or GC PM for a structural modification, then having no paper trail when the engineer challenges the change weeks later.
Recommended Process
Establish a field modification procedure at project kickoff: all modifications require written approval from the EOR before execution, even under time pressure. Keep a field modification log and submit it to the engineer at project close-out as part of the as-built record.