And what is a common unknown on construction projects? The exact location, size and presence of Underground Utilities.

Professional engineers, working with public and private infrastructure systems and projects, all too often encounter unexpected costs and delays due to inaccurate or incomplete utility drawings. Typically, the responsibility for providing accurate utility information is passed around from utility to owner to consultant to contractor. It is a problem that is not unique to Canada, it is common throughout North America and the world. We do not have accurate and reliable utility records that show the exact location of our underground utility infrastructure, and yet this information is crucial for increasing efficiency, reducing costs, and improving safety on construction projects. Examples of this problem are evident across the country every day, and it is time to come up with a solution.

In the United States a system has emerged over the last couple of decades to address this problem. Subsurface Utility Engineering, or as it is commonly known, SUE, combines traditional civil engineering practices with new technologies to develop reliable and accurate maps of underground utility infrastructure. The SUE process is effectively like setting up a common language that engineers, owners, contractors and utilities can all understand and utilize. SUE is recognized by the American Society of Civil Engineers (ASCE), and is detail in CI/ASCE 38-02: Standard Guidelines for the Collection and Depiction of Existing Subsurface Utility Data¹ which was published in January of 2003. The intent of this standard is to present a unified system for collecting and classifying utility data so that all parties can clearly understand what is being shown on drawings, and how that information was collected.

Managing the Risk

The main goal of any utility investigation is to mitigate the risk associated with encountering unknown utilities at the time of construction. This includes risk to personal safety, risk to the project schedule, risk to the project budget, and more. The key to mitigating that risk is to gather a sufficient level of information such that the engineer designing the Project can feel confident that there is a low probability of encountering problems in the field.

A SUE firm manages the risk associated with utilities by effectively managing the quality level of the data that is gathered during an investigation. It doesn't make sense to risk the success of a critical component of the project solely on the accuracy of a sketchy record drawing, nor does it make sense to install numerous test holes to determine the exact location of a utility that will have little or no bearing on the project. Almost every investigation should start with records' research and a survey of surface features. This gives a good sense of the congestion of underground utilities and can be used to make a decision on where additional effort is warranted. Additional steps can be taken, where required, to increase the data to quality level "B" or quality level "A". At the end of the investigation the utility drawing may show utilities at all four different quality levels from D to A, quality level D or C in the non-critical areas and quality level B and A where precise information is required.

Another major consideration is that the SUE firm responsible for the utility investigation stamps and accepts liability for the quality of the information collected. For this reason firms offering SUE services would possess a Certificate of Authorization, as well as carry liability insurance. These requirements give the project owner confidence in the information that is collected and portrayed.

Step by Step

The following is an example of how SUE principles are used on a typical construction project. Early on during the planning stages, the engineer responsible for the SUE investigation should advise the owner of potential impacts the project could have on existing subsurface utilities and recommend a scope for the utility investigation. The earlier the process is started, the greater the benefits that will be experienced.

Typically, the first step in the investigation is to gather utility records form all available source. This may include as-built drawings, field notes, distribution maps, and even oral accounts. All the records data should then be compiled into a composite drawing labeled as quality level D.

A site visit should be made to survey all the visible surface features of the existing subsurface utilities including manholes, pedestals, valves, etc. The survey may be conducted at the same time as the topographic survey completed for the project. This information can be used to help further define the location of utilities so that data can be increased to quality level C.

At this point a decision can be made as to which utilities may have an impact on the proposed design, and thus warrant the need for further investigation. Using a variety of geophysical techniques, the horizontal position of these critical utilities is designated. This information is surveyed and compiled into the utility drawings as quality level B data.

The final step in the data collection process is to install test holes at key locations where the exact size, material type, depth and orientation of the utility being investigated are crucial. The test hole information is surveyed and included in the utility drawings as quality level A data.

ALl the information from the investigation is compiled in a utility layer that can be included with the design drawing, or, based on the complexity, may be included as a separate utility drawing in the overall design package, The information is the available for the project designer, as well as for the contractor bidding and building this project. Having this reliable information not only increases the efficiency of the design process, but also has been shown to reduce contractors' bids and virtually eliminate extras associated with utility conflicts in the field.

Asset Management

The same SUE principals of using quality levels can be utilized when gathering subsurface utility information for asset management purposes. Managers of underground infrastructure know all too well that when workers find something in the field that contradicts what is shown on their records, immediately they assume all the information is wrong. Assigning a quality level to your data gives the user of the data a confidence level with regard to the spatial accuracy of the data. If it is labeled as quality level A they can be confident it is where the records say it is. Operators of asset management systems would start with quality level D and C and upgrade the information to quality level B and A in critical areas or on critical infrastructure. The overall goal again is to reduce the risks associated with the presence of these utilities within our right of ways.

Does it Work?

The Federal Highway Administration (FHWA) asked themselves the question after investing millions in grants for SUE projects throughout the U.S. They commissioned Purdue University to do a study of 71 projects that utilized SUE services, and determine the costs savings that were obtained as a result. The study found that for every $1.00 spent on SUE services, there was a savings of $4.62 in project costs². Although there are currently not enough projects completed to do a comparative study in Ontario, the results thus far have shown very similar results as were experienced in the U.S. The University of Toronto is currently working to gather what data is available and publish a comparable study for projects completed in Ontario³.

SUE in Ontario

SUE has been utilized on a wide variety of projects in Ontario over the last three years for a variety of users including the Ministry of Transportation of Ontario, Defense Research and Construction Canada, City of Toronto, City of Hamilton, and the Region of Durham. The results of those initial projects have helped to gain recognition and support of SUE by a number of key groups in the province, including the Ontario Sewer and Watermain Contractors Association (OSWCA), Ontario Road Builder Association (ORBA), and the Ontario Regional Common Ground Alliance (ORCGA). The ORCGA lists SUE as a reference for utility surveying that meets its best practices outlined for Planning and Design practices. Lower contractor bids, reduced delays, reduced redesigns, reduced utility relocations and improved project safety are only a few of the many benefits that users are experiencing. Project owners are seeing the benefits of utilizing SUE services, and their use is steadily increasing in Ontario. Engineers should be encouraged to learn more about SUE and begin utilizing the guidelines set out in the ASCE Standard, such that we can continue to advance towards more efficient engineering practices.

References
1. American Society of Civil Engineers. Return To Reading
(2003). Standard Guidelines for the Collection and Depiction of Existing Subsurface Utility Data. Standard #38-02, Reston, Virginia
2. Purdue University. Return To Reading
(Dec. 1999). Cost Savings on Highway Projects Utilizing Subsurface Utility Engineering. Prepared for the Federal Highway Administration, Washington D.C., as per FHWA.
3. University of Toronto. Return To Reading
Evaluation of the use of Subsurface Utility Engineering in Ontario. Contact: Mr. Hesham Osman, (416) 978-5964.

Credits
Author(s)
Lawrence Arcand  

Publication(s)
Canadian Civil Engineer
Spring 2005