In the early 1990s a major gas utility company in Ontario began the development of keyhole technology using long-handled tools to allow operations such as cast iron pipe leak repairs, service reconnections and the installation of cathodic protection, to be undertaken through a 450 mm diameter core hole in the pavement. This avoided the need for conventional open road cuts and reinstatement. To further enhance the benefits of this technology, a program of laboratory testing and field trials were undertaken in the City of Toronto (City) to allow efficient core removal, followed by vacuum excavation and finally a system that would allow the removed core to be used to permanently reinstate the pavement. Laboratory trials were undertaken on 20 potential bonding agents to identify a product that would be fast-setting with rapid strength gain so that repaired pavements could be opened to traffic in less than an hour. The cementitious bonding compound which was specially designed for the process was used on a number of field trials in the City. The reinstated cores were monitored for performance over a seven year period in sections of composite pavement. Based on the results of these trials, the procedure was approved for use in the City as a permanent utility cut repair. This keyhole technology and core reinstatement technology is now used widely throughout North America by gas utility companies. The cost savings are significant. In 2010, one utility company undertook some 4,500 keyhole cores and reinstatements, with an estimated cost savings of over $4 million when compared to conventional open cut procedures. In addition, with the reduction in materials, equipment time, and less traffic disruption, the sustainability benefits of this technology are significant. In some instances, the road can be re-opened to traffic within 30 minutes of the repair. This paper will review the development of this technology, other areas of application, and the benefits it offers in terms of providing a faster, better and more sustainable method for utility repair and maintenance.
