Page 19 - BCCGA Best Practices Version 3.0

18 British Columbia Common Ground Alliance
PRACTICE DESCRIPTION: SUE is applied during the design phase to locate,
identify, and characterize all existing utility infrastructure (and other relevant
non-utility features) found within a given project. SUE is applied in a structured
manner, in accordance with practices and Quality Levels found in ASCE 38-02
Standard Guideline for the Collection and Depiction of Existing Subsurface
Utility Data. Although the Standard is more detailed and comprehensive, a brief
summary of the Quality Levels are defined therein:
The four Quality Levels are as follows:
Quality Level D – Existing Utility Records: Information gathered solely from
existing utility records can provide an overall sense of how much congestion
there is around the utilities. The information, however, may be limited in terms
of accuracy and comprehensiveness. Information at this level should be limited
to project planning and route selection activities.
Quality Level C – Surveying Above Ground Facilities: Information gathered
from the surveying of above ground facilities, such as manholes, valve boxes,
pedestals, and so forth, is to enhance the information obtained at Quality Level
D.
Quality Level B – Surface Geophysical Techniques: This method involves the
use of surface geophysical techniques or “designating” (for example,
electromagnetic measurements, ground penetrating radar, induced
polarization, magnetometer, seismic surveys or shallow direct-current electrical
resistivity sounding) to determine the existence and horizontal position of
facilities, including those facilities found using the Quality Level C step. The two-
dimensional mapping information obtained is often sufficient for excavation
planning. The data can facilitate decisions regarding the placement of new
structures or facilities to avoid conflicts with existing facilities.
Quality Level A – Non-destructive Excavation: The use of non-destructive
excavation devices or “locating” at critical locations can determine the precise
horizontal and vertical positions of existing facilities. This method can also
determine the type, size, condition, material, and other characteristics of the
facilities. A precise plan and profile information on the facilities can assist in
making final design decisions. As well, a Subsurface Utility Engineer can
guarantee the accuracy of the information gathered at this level.