Quality Level D (QL-D)

The lowest ASCE 38 quality level: utility information taken from existing records and verbal recollection, with no field verification of any kind.

QL-D is where every project starts, because records research is the cheapest step. Its reliability is entirely a function of the source, and the failure modes are well known — field routing changed during construction, later repairs rerouted segments, additions were made by whoever was on site, and some records are simply missing. Treating QL-D as if it were QL-B is the most common way a design ends up in conflict with something that was always there.