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Utility Mapping

UTILITY MAPPING IS OUR PRIMARY SERVICE

We not only map utilities, but we indicate the reliability of the mapping via a "quality level" attribute. Each line segment has its quality level differentiated by line code and label and/or symbol. The four quality levels - "QL D", "QL C", "QL B", "QL A" - represent an increasing level of assurance to the project owner, designer, and constructor that the utility as shown on the plans is where it actually may be found on the project site. So-Deep first introduced these concepts of utility quality levels to the nation in the 1980s. They are rapidly becoming the standard of care throughout the civil engineering profession. The American Society of Civil Engineers published a national standard (ASCE/C-I 38-02), chaired by a So-Deep principal, entitled Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data that further defines this concept.

"Quality Level D"

Information derived from existing records or oral reports and testimony.  This information is great for planning and preliminary budgeting purposes.  Its effectiveness is limited during design and construction phases of a project.

"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 information. This was the traditional level of effort put into utility mapping during design phases of a project before the advent of subsurface utility engineering.

"Quality Level B"

Information obtained through the application of appropriate surface geophysical methods to determine the existence and approximate horizontal location of existing subsurface utilities.  Appropriate surface geophysics typically include a wide variety of pipe and cable locators (frequencies and manufacturers), magnetics, terrain conductivity, elastic wave methods, and may include GPR, thermal methods, and others.  QL B data has its best return on investment when used very early in the design process.

"Quality Level A"

Precise horizontal and vertical location of utilities obtained by the actual exposure (or verification of previously exposed and surveyed utilities) and subsequent measurement of subsurface utilities, usually at a specific point. Minimally intrusive excavation equipment is typically used to minimize the potential for utility damage. A precise horizontal and vertical location, as well as other utility attributes, is shown on plan documents. Accuracy is typically set to 15-mm (0.05 foot) vertical and to applicable horizontal survey and mapping accuracy as defined or expected by the project owner.  Most QL A data are acquired at the beginning of final design, where small adjustments to cut & fill, structure elevations, structure position, or structure type can avoid existing utility relocations.  However, some QL A data may also be prudent during planning, preliminary design, and construction.

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