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Subsurface Utility Engineering

A Process Named SUE

Southwestern Region is assessing a new utility location/identification process to ensure project employees have all the information they need on the job. This process, called Subsurface Utility Engineering (SUE), identifies utility infrastructure buried underground, and is intended to help keep projects on-time and on-budget, minimize work-related delays, and improve safety. The interchange upgrade at Homer Watson Blvd. and Highway 401 in Kitchener is the first MTO project to use this process. This pilot will help MTO determine the benefits of SUE for future detail design projects.

In a SUE investigation, utility line information can be identified to four increasing levels of quality. Staff must determine the potential impact of each utility and decide what quality of information is critical to safety and efficiency. Utilities that have only minor impact need only minimal investigation. Quality level D, the level of least detail, entails information about a utility gathered only from existing records and oral accounts. Quality level C supplements this with a visual survey of the aboveground indicators of utilities, such as manhole covers. The engineers then determine how this data fits in with the information from quality level D. Generally, a utility in a non-critical area of a project will suffice with only level D or C information. The higher the quality level, the more time and resources required.

When utility lines can have a crucial effect on a project's progress, quality level B or A is essential. Quality level B is achieved by using geophysical prospecting techniques, such as electromagnetic cable locate equipment and ground-penetrating radar, to determine the horizontal position of utilities. This creates a two-dimensional map for engineers. Quality level A involves installing test holes to gather data about the utility's size, orientation, material type, and depth, thus creating a precise, three dimensional map of the utility.

Why is utility data so vital in a project? Inaccurate utility data, during the design stage, is typically one of the leading causes of cost increases and construction delays on projects. In addition, an accidentally cut utility line can cause major inconveniences for the people it services, and can also endanger personal safety and lives. It is imperative that both the designer and laborers can get the best information they can when working on a project.

Southwestern Region selected the Homer Watson Blvd. /Highway 401 interchange upgrade for this SUE trial because of the nature of the project. The scope of this project is extensive, including bridge replacement, building new ramps, reconstruction and realigning some of the existing ramps, and expanding the commuter parking lot. This interchange has a variety of utilities, a high volume of traffic, and a limited right-of-way for construction, making it a good candidate for a pilot use of the SUE process.

SUE is a part of MTO's effort to prepare contract packages with more accurate information. It also shows MTO's continuing efforts to mitigate construction conflicts, delays, and claims. Construction on this project is expected to begin in spring 2005.