The American Society of Civil Engineers (ASCE) has developed an important standard of care guideline which breaks up SUE investigations into four quality levels of utility depiction:
Quality Level D – Information derived from existing records or oral recollections. This would include historical plan research, aerial imagery, etc.
Quality Level C – Information obtained by surveying and plotting visible above-ground utility features and by using professional judgment in correlating this information to Quality Level D.
Quality Level B – Information obtained through the application of appropriate surface geophysical methods (i.e. ground penetrating radar, radiodetection) to determine the existence and approximate horizontal position of subsurface utilities. This information is correlated with Levels C and D.
Quality Level A – Precise horizontal and vertical location of utilities obtained by the actual exposure and subsequent measurement of subsurface utilities, usually at a specific point with soft digs (i.e. hand dig, air knife).
End Product- This information is compiled and drafted into an as-built plan that can be used by many different construction disciplines for planning and maintenance.