| Subsurface Utility Engineering:
Cutting construction costs and claims with reliable underground utility information
Since people began building civil infrastructure in North America the task of obtaining reliable, accurate, and up-to-date information about the location of underground utilities has been a formidable one. While the location of these subsurface utilities might be found on plans and records, all to often it is the contractor that discovers the utilities are not where the records say they are. Owners, designers, engineers, and contractors have learned the hard way that the lack of accurate utility information can result in costly conflicts, damage, delays, service disruptions, redesigns, claims, injuries, and the loss of life.
There is, however, a process gaining broad acceptance in the United States and Canada that can provide this much-needed utility information. Subsurface Utility Engineering (SUE) combines civil engineering, geophysics, and surveying to produce accurate and reliable maps of existing underground utilities.
A proven methodology, widely used in 38 American states, SUE is being introduced to Ontario by TSH/TBE Subsurface Utility Engineers JV, a partnership of TSH, an Ontario-based engineering firm, and the TBE Group of Clearwater, Florida, the leading provider of SUE services in the United STates. To date, TSH/TBE has undertaken SUE assignments for the City of Toronto, and the Regions of Durham, Niagara, and York. Bruce Miller, senior vice-president, highways with TSH, and the director responsible for the joint venture says: "So far, the results have been very encouraging. The feedback from our clients has been very positive, and our investigations have provided a level of information that has been effectively utilized in the design stages of the projects involved".
The SUE Process
Subsurface Utility Engineering involves four major professional activities - records research, designating, locating, and data management. Records research is the starting point for any utility investigation. However, the information gathered can not be considered accurate until it is verified through designating and locating. Designating involves the use of geophysical prospecting techniques to determine the existence and horizontal position of underground utilities. Locating utilities non-destructive excavation, such as vacuum excavation, to install test holes at critical points along a subsurface utility's path to determine its precise horizontal and vertical position. Data Management is the surveying of utility information obtained through designating and locating, and the entering of that information into the client's computer-aided design and drafting system. The cumulative effect of the process is to provide a reliable, and accurate map of the underground utilities within project design plans.
Clients who contract for SUE services can receive four quality levels of information. Level D is the most basic level of information, and it is obtained through an examination of existing plans and records. Level C supplements Level D information with a visual ground survey of utility facilities, such as manholes and valve boxes. Level B is the first quality level where SUE designating information is used, and it provides two-dimensional horizontal mapping information. Level A is the highest quality level of accuracy and involves the augmenting of Level B information with test hole data to provide precise three-dimensional horizontal and vertical mapping of utilities and related structures.
Lawrence Arcand is the TSH/TBE JV SUE project manager and he points to two recent SUE assignments as evidence of the effectiveness of the process. "The City of Toronto requested SUE levels A and B during the design phase of a water main rehabilitation project at the intersection of Kipling and Evans Avenues in Etobicoke. Our investigation showed that a telephone duct system and electric transmission facilities were in conflict of the original design so design changes were made well in advance of construction. We are being told that the contractor estimated that its bid was reduced by 5% due to the accuracy of the utility information provided.
On another project, for Durham region in the City of Oshawa, SUE services accurately verified the location of the gas main in the corridor, and eliminated the need to relocate that gas main to accommodate the project, said Arcand.
Savings Fourfold Plus
Initial SUE results in Ontario seem to be in line with the U.S. experience. Studies done for the Federal Highway Administration (FHWA) show that for every dollar spent on SUE services there was a savings of $4.62 in the overall cost of the project. Moreover, the studies revealed that there were fewer delays due to utility conflicts, claims were reduced, and there was an overall improvement in construction safety.
FHWA endorses the use of SUE on all highway/bridge design projects. But Paul Scott, formerly of the FHWA Office of Engineering, and now a senior consultant with the TBE Group, says incorporating SUE makes good engineering and design sense for any type of construction project - building, airport, utility, transit, or any other public works construction - requiring excavation around existing underground utilities. According to Scott: "SUE enables owners or engineers to locate those utilities early in the design process when inexpensive design decisions and alterations can be easily made".
Bruce Miller believes that the need for SUE will grow as municipalities move to upgrade and rehabilitate the existing urban infrastructure. "While SUE services are a cost at the design stage of any project, the benefits of reduced utility damage, reduced claims, reduced delays, improved safety, and reduced overall project costs will outweigh any concerns that clients might have. Moreover, the detailed information generated will assist both municipalities and utilities in better managing their capital assets in the future".
Author Not Identified
The Road Builder
Fall / Winter 2003