Accidental damage to underground utility facilities during highway construction results in lost lives, serious injuries, project delays, and aggravating service disruptions. This has been a problem for many years. Subsurface Utility Engineering (SUE) is proving to be a viable solution.

SUE is an engineering process that locates underground utilities during the early development of a highway project. However, it is not limited to highway work. It can be used on any public works project and in conjunction with any excavation activity.

SUE involves two major activities: designating and locating. These activities are best defined in terms of quality levels of information. There are four recognized quality levels, beginning with Quality Level D (QL-D) and ascending to Quality Level A (QL-A).

* QL-D is the most basic and least desirable level of information. It comes solely from existing utility records. It may provide an overall "feel" for the congestion of utilities, but is often highly limited in terms of comprehensiveness and accuracy.

* QL-C is probably the most commonly used level of information. It involves supplementing QL-D with above-ground survey information that depicts visible utility facilities, such as manholes. Although better than the QL-D information, it is not unusual when using QL-C to find that 15 to 30 percent of the underground utilities are either omitted or are plotted two feet or more in error.

* QL-B is the first level where SUE information is used. It involves supplementing QL-D information with "designating" and supersedes the need for QL-C information. Designating is the use of surface geophysical techniques to determine the existence and horizontal position of underground utilities. This provides information for two dimensional horizontal mapping and is usually sufficient to accomplish preliminary engineering goals. Decisions can be made on where to place storm drainage systems and other design features to avoid conflicts with existing utilities. Slight adjustments in the design can produce substantial cost savings by eliminating utility relocations and moving excavation work away from utilities. Even so, the designer still does not know the vertical position of the underground utilities.

* QL-A information is the highest level of accuracy presently available and involves full use of the SUE services. It involves adding "locating" to the QL-B information. Locating is the use of the nondestructive digging equipment at critical points along a subsurface utility's path to determine the precise horizontal and vertical mapping. The use of nondestructive digging equipment, such as vacuum excavation, eliminates damage to underground utility facilities caused by backhoes. The small work area involved, 20 x 20 centimeters at the top of the hole, eliminates pavement damage traditionally caused by backhoes. Knowing exactly where a utility is positioned in three dimensions, the designer can often make small adjustments in design elevations or horizontal locations and avoid the need to relocate utilities or excavate near them.

Eliminates Delay, Accidents

The use of QL-A information benefits highway projects by eliminating unexpected conflicts with underground utilities during construction. This, in turn, eliminates unexpected deaths, injuries, project delays, and service disruptions.

There are consultants that do the SUE work. They designate and locate to desired levels and transmit resulting data in a format compatible with the highway agency's computed aided drafting and design (CADD) system. They do everything necessary to accurately characterize underground utilities. THey are professional engineers, professional geologists, and licensed surveyors. They provide a set of plans or just the information to go in the plans. They seal their work and stand behind it. They take full responsibility for the accuracy and comprehensiveness of all utility information provided and they have adequate insurance to back them up.

The Virginia Department of Transportation (DOT) has been using SUE since 1984. Twenty or more other States highway agencies are using it too in some manner, including big users such as Maryland, Pennsylvania, Delaware, North Carolina, and Arizona. In addition to State highway agencies, a number of city and county highway agencies use SUE. In Arizona, the City of Phoenix and Maricopa County use it. In northern Virginia, Fairfax County has been using it since 1980. Engineers at the Federal Highway Administration (FHWA) are not aware of any highway agency that has SUE and been unhappy with it. Usually it is just the opposite - for first-time users accelerate their use of SUE once they see what it can do for them.

SUE is relatively inexpensive to use. It typically costs less than one percent of the total cost of a highway project: whereas project savings may approach $15 or more for every dollar spent for SUE, and the time required to design a project may be reduced by as much as 20 percent.

Success stories abound. Many have not been documented because the benefits have been so obvious. But, several have:

*On a major highway project in Virginia, the Virginia DOT's consultant designated utilities dug 156 test holes at locations where it was thought highway/utility conflicts were possible. Using the data obtained, the DOT's roadway and hydraulics designers determined that conflicts would occur at 75 of the sites (almost half). As a result, design changes were made and 61 (almost 80 percent) of the potential conflicts were eliminated. By making these changes, $731,425 worth of utility adjustments were avoided; whereas, the cost of SUE was only $93,553, resulting in a savings of $637,872.

$56,000 Saves $1.3 Million

* On a highway project in Maryland involving realignment of a state road and widening from 2 to 6 lanes, the use of SUE enable the Maryland State Highway Administration (MSHA) to minimize conflicts with utilities. Instead of impacting about 5,000 feet of each utility (gas, water, and sanitary), conflicts were reduced to about 400 feet. The cost for SUE was $56,000. Combined cost savings to MSHA and the utilities amounted to more than $1.3 million.

*The Florida DOT found that it save $3 in contractor construction delay claims for $1 spent for SUE

*The Columbus Southern Power Company in Ohio used SUE during the design of 1.2 miles of a 138 kV electric pipeline through the downtown area of Columbus. The cost of SUE was less than $100,000. Subsequently, the successful bidder for construction stated that it has been possible to reduce its bid price by $400,000 due to the availability of reliable utility information. Furthermore, there were no utility relocations, no utility change orders, no contractor claims, no utility damages during the project, and the project was finished ahead of schedule.

It is impossible to determine how many lives have been saved or how many injuries have been avoided as the result of using SUE on highway projects. It is only known that SUE has dramatically, some believe totally, reduced unexpected conflicts with underground utilities on projects where it has been used.

Complements One-Call

In addition to all of the above, SUE complements the One-Call systems that have been established in the United States to aid in the prevention of damage to underground utilities. SUE services are provided early in the development of a project, years before the excavators go to work, early-on when plans can be changed and conflicts avoided. The results of the SUE investigations are comprehensively and accurately plotted on highway plans. Even so, utilities depicted on plan sheets may be overlooked, excavators may not understand how to read the plans, there may be such a rush to complete work that shortcuts are taken, etc. One-Call is needed to mark the utilities' locations on the ground just before the excavators go to work. Typically, the SUE information obtained early in project development will be made available to One-Call. SUE and One-Call working together can virtually eliminate unexpected conflicts with underground utilities.

There is a great need for the highway agencies to begin using SUE. The FHWA believes it should be used on any highway project which is likely to involve conflicts with underground utilities. The FHWA estimates that when all highway agencies are routinely using SUE, the nationwide savings will be more than $100 million per year. This figure does not include savings in lives, injuries, and service disruptions, but those savings will be substantial. Unexpected encounters with underground utilities will almost be a thing of the past.

Credits
Author(s)
C. Paul Scott 

Publication(s)
Underground Focus
Nov/Dec 1994