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Subsurface Utility Engineering
The inability to obtain reliable underground utility information has long been a troublesome problem for highway designers in the United States. Many States utilize consultants to identify the quality of subsurface utility information needed for highway plans, and to acquire and manage that level of information during the development of highway projects. This engineering practice is known as Subsurface Utility Engineering (SUE).
Subsurface Utility Engineering: An Introduction
SUE is an engineering practice that has evolved considerably over the past few decades. The SUE process combines civil engineering, surveying, and geophysics. It utilizes several technologies, including vacuum excavation and surface geophysics. Its use has become a routine requirement on highway projects in many states.
Since 1991, the FHWA has been encouraging the use of SUE on Federal-aid and Federal Lands Highway projects as an integral part of the preliminary engineering process. Costs for SUE services are eligible for Federal participation.
The proper and successful use of SUE benefits both highway agencies and the impacted utilities in the following ways:
SUE Standards and Definitions
The American Society of Civil Engineers' (ASCE) Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data was published and distributed in 2003. The ASCE standard makes it very clear that SUE is a process, not a technology. It defines SUE as a branch of engineering practice that involves managing certain risks associated with:
These activities, combined with traditional records research and site surveys, and utilizing new technologies such as surface geophysical methods and non-destructive vacuum excavation, provide "quality levels" of information.
SUE Quality Levels
Quality levels may be thought of as degrees of risk, or how much information is really needed to adequately design and construct a highway project. Highway plans typically contain disclaimers as to the accuracy of the utility information. The use of quality levels allows project owners to decide what quality level of information they want to apply to their risk management challenge and to certify on project plans that a certain level of accuracy and comprehensiveness has been provided.
There are four recognized quality levels of underground utility information ranging from Quality Level (QL) D (the lowest level) to Quality Level A (the highest level).
The highest level of accuracy and comprehensiveness is generally not needed at every point along a utility's path, only where conflicts with highway design features are most likely to occur. Hence, lesser levels of information may be appropriate at points where fewer conflicts or no conflicts are expected.
Each of the four quality levels is described as follows:
How SUE Works in Project Development
The highway agency assumes responsibility for taking appropriate actions to consider and deal with utility risks. On many small projects, where few subsurface utilities are present, and/or where information about subsurface utilities is believed to be generally accurate and comprehensive, this will only involve making a conscious decision to proceed with the project using readily available information. On larger, more complex projects, the state highway agency may elect to employ the services of a SUE provider to obtain expert advice and to use available technologies to provide better information.
The engineer, when involved, will advise the highway agency of utility risks and recommend an appropriate quality level of utility data as described above for a given project area at the appropriate time within the project planning and design process. The highway agency will then specify to the engineer the desired quality level of utility data.
The engineer will furnish the desired utility quality level to the highway agency in accordance with the standard of care and will be responsible for negligent errors and/or omissions in the utility data for the certified utility quality level .
Additional Information about SUE