Subdrain

A pervious backfilled trench containing a pipe with perforations or open joints for the purpose of intercepting ground water or seepage.

Subgrade

The surface of a portion of the roadbed on which paving, or railroad track ballast, or other structure is placed.

Subsidence

The settlement of the ground, pipeline or other structure. The effects may not be evenly distributed and differential settlement may occur.

Substantial Completion

The stage in construction when a project can be utilized for the purposes for which it was intended. At substantial completion, minor items and items that are seasonally restricted need not be completed, but the items that affect operational integrity and function of the facility must be capable of continuous use.

Sulfide Stress Cracking (SSC)

Brittle failure by cracking under the combined action of tensile stress and corrosion in the presence of water and hydrogen sulfide.