Alberta Transportation Ministers Award for Innovation
Sep 2015 • Civil Infrastructure • Article
Across North America, roadway and drainage asset owners are facing a backlog of aging infrastructure, whose deterioration rate is exceeding the ability and budget to replace it. Many owners are forced into a cycle of reactive, rather than proactive maintenance, repairing and replacing assets as they fail, rather than at the optimal time. This approach compromises safety and costs far more money, in both the short and long term, than a proactive asset integrity management approach. In an ideal world, asset owners would be able to replace all critical structures in advance of their failure, however this would exceed any realistic budget, be wasteful and socially disruptive. With advances in technology, high quality non-disruptive condition assessment data is now available which can be used to both optimize an individual asset’s service life and to form the basis for a long term highly effective asset integrity management program for the entire inventory.
The robust condition assessment of an asset improves the outcomes associated with the management of that asset and is the basis for the innovation presented in this nomination. Applying new non-destructive testing techniques to the condition assessment of highway drainage structures enables the full understanding of the asset’s structural integrity. With full information, repair and rehabilitation efforts can be designed using the most appropriate techniques to address all structurally significant issues presented by the condition assessment.
The specific condition assessment process is trademarked SoilSight™ and is being used in jurisdictions across North America to evaluate the structural condition of corrugated metal pipe (CMP) assets, often used as culverts, storm sewer or levee structures. CMP structures are inherently reliant on the surrounding soil for structural stability and prior to the introduction of this innovation, the soil structure was impossible to inspect in a non-destructive fashion. SoilSight™ condition assessment is the innovation and a compelling use case for its value as well as applicability and adaptability to Provincial Departments of transportation has been developed in conjunction with the New Brunswick Department of Transportation and Infrastructure.
During the 2015 condition assessment project, 14 culverts were put through the condition assessment protocol and a rehabilitation recommendation was designed based on the structural state of each specific asset. Each of these 14 culverts are part of the Departments “Strategic Corridors” supporting infrastructure and were included as top priorities in this project for that reason. To summarize, one (1) of the culverts was recommended for replacement because none of rehabilitation options that were technically possible were economically viable. Four (4) of the culverts were recommended for continued monitoring as they were in stable condition. And, nine (9) of the culverts were considered excellent candidates for trenchless rehabilitation. These nine culverts each had site specific rehabilitations designed as a part of the project and engineers estimates were applied to them. The culverts ranged in depth of bury, length and diameter but in all instances the rehabilitation cost was significantly less costly than the replacement of the culvert. The range of savings for each pipe was 50%-80% on construction cost and the total savings for this project was estimated to be a minimum of $7 million.
The rehabilitation methods applied to the pipes are all techniques used regularly in North America which can all be adopted and sourced using contractors locally available. These methods include many trenchless techniques such as Centrifugally Cast Concrete Pipe liner, Spray in Place Plastic Pipe liner, Slipline and soil stabilization using chemical and cellular grout. Soilsight™ is the multi-tool process, and innovation being nominated, that enables these trenchless techniques to be applied with confidence as the soil envelope surrounding the existing pipe can be verified prior to rehabilitation. It uses a tablet based software system called InScribe™ and a backscatter computed tomography imaging system called Insight™ (Inversa’s patented portable CT scan). InScribe™ is used to capture all field information associated with SoilSight™ for transmission, storage and report generation. Insight™ is the first CT scan for infrastructure, providing meaningful and easy-to-interpret diagnostic images that make critical maintenance decisions crystal clear. When deployed, the scanner produces an image from inside the pipe, through the pipe wall, into the supporting soil to evaluate the soil envelope’s integrity. The system uses the relative density difference between different materials to create an image of whatever is in the scan field by measuring the ‘backscattered radiation from each point within the scan domain.
The condition reports produced by SoilSight™ include several important pieces of information:
- An industry leading visual inspection based on protocols from 15 jurisdictions across North America including Alberta Transportation.
- Acoustic inspection or “knock test” results, screen 100% of the pipe for areas that present potential undermining or soil voiding.
- Plan profile map of the structure, used to evaluate deformation of the pipe, vertical pipe alignment and depth of cover from road to pipe.
- Ovality measurements, which are important indicators of structural instability.
- Insight™ diagnostic imaging results, used to verify the soil structure at all regions of interest.
Alberta Transportation – Structural Condition Assessment of Bridge Sized Culvert
The Government of Alberta Ministry of Transportation requested the structural condition assessment of a bridge-sized culvert located North of the Edmonton International Airport on Highway 19. The culvert is 2.4 meters in diameter, 340 meters in lineal length and is under more than 34 meters of cover at the deepest location.
Over the preceding years, there has been some deflection of the culvert shape at selective rings and the replacement of the asset was being considered. Initial estimates were approximately $10 million for the project. Alberta Transportation had suspicions of void/ instability around the culvert due to geotechnical settlement and pipe deformations. The focus of the project was to use Inversa System’s condition assessment procedure, SoilSight™ to conclusively determine the structural integrity of BF 8958 and guide trenchless rehabilitation efforts. Alberta Transportation wished to identify all relevant structural issues regarding the pipe including where the pipe is unsupported. The results were provided in a condition assessment report and an elegant rehabilitation recommendation was outlined to conclude the project. The proposed repair option is a partial repair estimated at a cost of $4 million. This rehabilitation would safely and effectively extend the useful service life of the asset in a comparable way to installing a new structure and can all be done without disrupting service of the road. “The BCT scanning has given us confidence in the soil structure around the pipe,” says Amy Driessen of Alberta Transportation and it is estimated that the rehabilitation will extend the service life of the culvert 30-40 years.
Proactive asset management planning using robust condition assessment information and the most effective techniques results in optimized asset life cycle and expenditure in the short term and into the future. Innovation means to use new ideas, methods and products to enhance the way our systems function. By applying new tools to old problems, organizations can significantly improve service delivery at a reduced cost. This project shows how approximately $7 million could be saved on a single culvert project. This process has the potential to save significantly more when applied systematically to a larger section of the inventory in an asset management program.