Smart sustainable planning starts with SUE
With budgets getting tighter and infrastructure getting more complex, municipalities must come up with innovative ways to manage spending. A key element in any project is the design phase – without proper planning the project cannot succeed.
In 2003, the American Society of Civil Engineers (ASCE) provided a guideline for a branch of civil engineering called SUE (subsurface utility engineering). When conducted early in the design process, SUE provides critical data on the exact location of existing utilities in the project area. One prime example for the use of SUE on a large scale trenchless project is the Eglinton Crosstown Light Rail Transit (ECLRT) line, located in Toronto.
The project forms part of “The Big Move,” a 25-year regional transportation plan for the Greater Toronto and Hamilton Area (GTHA) worth $50 billion. The plan was launched by Metrolinx in September 2008.
One of the projects currently underway in the first wave of “The Big Move” is the ECLRT line,which represents an investment of $5.3 billion (2010 dollars) towards better transit in Toronto.
The ECLRT is a light rail transit line that will run across Eglinton Avenue between Mount Dennis (Weston Road) and Kennedy Station. This 19-kilometre corridor will include a 10-kilometre underground portion between Keele Street and Laird Drive, that will be installed with the use of Tunnel Boring Machines (TBMs).
With proper planning and the use of the SUE information provided by T2 Utility Engineers (T2ue), inherent underground utility issues were dealt with upfront during the design stages of the project. The use of SUE processes built a solid understanding of the current conditions that allowed for the proper planning needed to manage the utility relocations and protection schemes for the new ECLRT.
Identifying underground utilities with SUE
Transit City/AECOM/IBI hired T2ue to complete a SUE investigation of eight distinctive areas from Bicknell Drive to Avenue Road in Toronto. This included Keele, Caledonia, Dufferin, Oakwood, Bathurst, Chaplin and Avenue Stations.
The purpose of the utility investigation was to clearly identify the location of existing underground utilities in order to facilitate the design for the new ECLRT system. The investigation focused on telecommunications, gas, electrical, steam, water, pipes and sewers. T2ue collected and analyzed all available utility records and information from Transit City/AECOM/IBI and utility companies in the area.
T2ue used geophysical technologies such as: electromagnetic pipe and cable locators, CCTV and ground penetrating radar (GPR) to determine the horizontal and vertical alignments of utilities. All alignments were surveyed and information was extrapolated into a composite utility design showing the existing utilities at the appropriate Quality Levels in accordance with the ASCE 38-02: Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data. Test holes were then installed at critical locations using vacuum excavation equipment, allowing for precise X, Y, Z coordinates on key infrastructure.
The investigation was successful in confirming and further refining the location of the existing utilities. Few notable findings during the investigation included undocumented storm and sanitary sewers, as well as abandoned watermains and gas mains. Some of these findings would have had a significant impact on the project that could have caused delays and design issues.
The lessons learned from this large scale trenchless project can be applied on all future trenchless projects, regardless of size or scale. The most important factor is obtaining reliable information and quantifying the quality levels by a set standard such as CI/ ASCE 38-02 SUE mapping. By providing the information upfront during the design process, the need for costly redesigns, relocations and surprise delays is greatly decreased. The exposure to risk for the project owner (in this case the tax payers of Ontario) can be properly managed using SUE.
For this project, which is located within an existing dense urban environment, the use of trenchless methods, specifically the TBM, was ideal. For this method to work effectively however, a reliable understanding of the underground utility network is required. Without the use of SUE, the depiction of the existing utilities would have been based on a patch work of old maps creating a very unreliable basis for the design. This could have potentially have led to millions of dollars in cost overruns and countless delays. By adding SUE to the equation, a standard is set for the quality of information being processed. Having the ability to question and then peruse the right information needed to complete such a project is paramount for budgeting and overall feasibility for the decision of what technology and method will be used during construction.