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Keyhole Studies and Reports

New Approaches to Utility Cut Pavement Repair Final Report (2016)



On August 22nd , 2014 the Federal Highways Administration (FHWA), pursuant to FWHA-PROJ-14-0015, awarded an Engineering and Technical Services contract to NTH Consultants Ltd. to carry out a study to comprehensively research and evaluate effective and durable approaches to the repair/restoration of utility cuts in asphalt and Portland cement concrete pavements.

The scope of research was not limited to the United States; indeed, it was of interest to the FHWA to explore what other countries were doing in this subject area. The study will document, assess and determine the efficacy of repair/restoration of pavements in the context of cuts to access buried utilities or other subsurface facilities. Particular emphasis will be placed on urban conditions where utility cuts occur frequently, and the desire is to
minimize their impact on both the highway agency infrastructure and the traveling public.

The research effort will focus on proven effective and novel, non-conventional and experimental techniques, with the scope of the investigation extended beyond North American practices. The analysis will document the effectiveness of each practice and make recommendations on techniques roadway agencies and utility companies should employ. Emphasis will be placed on urban applications.

Over the next two years the Research focused on the examination of four pavement utility cut and restoration methods including (a) Conventional Pavement Cut and Replace; (b) Infrared Repair; (c) Precast Concrete Pavement Sections; and (d) Keyhole Excavation.

The Final Report, submitted in March 2016, provides an evaluation of the benefits and constraints of each of those methods that roadway and utility owners can use to establish best practices to guide themselves toward repair method selection as an overall practice and on an individual project basis.

Pacific Gas and Electric (PG&E) Uses Keyhole Coring and Reinstatement Technology November (2017)


Keyhole Technology has allowed PG&E in Northern California to significantly increase its operational efficiencies in performing a number of critical gas operations. For example, a few years ago, a typical crew using conventional methods, would have been able to complete one or two T-Cap replacement jobs in a day. Now, with keyhole technology, that same crew is able to complete ten of those same jobs in a day. A five-fold increase in efficiency and a five-fold decrease in public inconvenience.

In addition to being environmentally friendly, PG&E has found that Keyhole Coring and Reinstatement can reduce pavement restoration delays and public inconvenience from what typically used to be an average of 10 days to just one day – the same day the work was performed.

Keyhole Technology is a Safer, Better and more cost-effective way of performing many gas operations services in the streets and is much more convenient for the public than conventional pavement excavation and repair methods.

Why Cities Are the Frontline Defense Against Climate Change, 2019



Cities and other urban areas consume more than two-thirds of global energy and emit more than 80 percent of the world’s total greenhouse gases, and many, because of their location, are expected to suffer the most significant consequences of climate change.

This paper identifies how cities can use keyhole coring and reinstatement technology to reduce both GHC emissions and costs. By performing utility cuts using keyhole technology, GHC emissions can be reduced from 845lbs for a conventional excavation and repair to 69lbs per cut as well as reducing costs by up to 87%.

APWA Reporter, September 2009: Keyhole coring and replacement: the right solutions for right-of-way owners.

MURVYN MOREHEAD, Right of Way Manager, City of Overland Park KS, DENNIS JARNECKE, Principal Project Manager, Gas Technology Institute, Des Plaines IL, and T. MARK ANDRAKA, Senior Engineer, PECO Energy, Philadelphia PA, explain the advantages and benefits of Keyhole Coring and Replacement for ROW owners, utilities, the public, and the environment. It's a fact of life for every right-of-way (ROW) owner: At some time or another, there will be a need for repairs to the utility infrastructure under your roadways. Keyhole coring and replacement is the best solution for everything from the simplest daylighting, to exposing the utility, to major line replacement. Coring is a better, smarter, and environmentally sensitive way to make and repair utility cuts through pavement.

Our Planet Magazine 2009


Our Planet was a syndicated television magazine that aired across North America in 2009 on CNN Business News and other local networks. Hosted by Greg Gumbel, each episode explored important new, innovative and sustainable environmental technologies that can help make a difference in our daily lives. On this episode that aired in in 2009 on a variety of local stations, Our Planet explains how Keyhole Coring and Reinstatement can help to reduce the impact of pavement utility cuts needed to repair and maintain the more than 20 million miles of gas, water, sewer and telecommunications infrastructure that lies buried under the nation’s six million miles of paved roadways.

January 2007: American Water Research Foundation (AWRF) “No-Dig and Low-Dig Service Connections Following Water Main Rehabilitation Report” recommends Keyhole Technology for reconnecting service laterals following pipeline rehabilitation and trenchless construction methods.


The AWRF has identified the expense and disruptive nature of reconnecting service lateral pipes as a significant impediment to greater use of water main rehabilitation techniques. The emergence in recent decades of various pipeline rehabilitation and trenchless construction methods had raised the hope that more work could be accomplished with limited funds, but the added cost to reconnect service laterals when using these methods has often disappointed. By the time that holes are excavated to tie each service lateral to a main installed or rehabilitated with trenchless technology, the project begins to resemble the open-trench projects that the water utility is trying to avoid—and so do the costs. This study, among other things, helps to resolve this problem by identifying ways in which laterals can be reconnected in “no-dig” and “low-dig” manners by utilizing keyhole techniques to efficiently perform the necessary tasks. (See:  pp. xix, 14, 21, 48-51, 65-75, 106.)

ROAD UTILITY CUTS - National Research Council of Canada and U.S. Army Corps of Engineers Field Investigation
Toronto Site


The research and development project entitled "Restoration of Utility Cuts (RUC)" is a joint effort involving a number of North American organizations including cities, utility companies and U.S. State departments of transportation. The objective of the project was to develop a guide for best restoration practice based on sound engineering principles. The National Research Council Canada and the U. S. Army Corps of Engineers have joined forces and built a collaborative research project, which investigated the problem and developed the necessary corrective measures for restoration practices that lead to poor performance in the past. The project was managed by a steering committee formed from member organizations contributing to the consortium.

The Toronto field experiment was one of five RUC project sites selected to cover a wide range of utility cut restoration practices and environmental conditions. The Toronto experiment offered an opportunity to investigate the use of unshrinkable fill, a concrete low strength material (CLSM), as a backfill for reinstating utility cuts. City of Toronto specifications for unshrinkable fill follow general flowable fill material guidelines and have been used effectively since 1988. The city manages the quality of this material through a certification system that produces a list of approved unshrinkable fill suppliers (current list includes approximately 20 manufacturing plants). The experimental site included two cut sections, a conventional transverse trench and a keyhole. This report discusses the outcome of in-situ tests conducted in Toronto and laboratory investigations performed at the NRC campus in Ottawa.

The Golder Report - Longitudinal testing and report on the keyhole coring process


This study is an update of the work carried out over the previous ten years on the materials and installation methods used to repair or install subsurface utility plant using Keyhole Technology. Keyhole Technology was originally developed by The Consumers Gas Ltd. (now Enbridge Gas Distribution) over the ten years. The method developed is less intrusive employing, among other things, a rotary cutter and improved pavement reinstatement techniquires including a propietary pavement cutting drill to remove the pavement surface. Using the cutter, the pavement coupon is removed and preserved. The hole is vacuum excavated to expose the plant and the repair iof the plant or installation of new equipment is achieved using long handled tools. After the reapir, the hole is backfilled and the pavement coupon is reinstated with a proprietary bonding compound (Utilibond) bonding the coupon back into place as a permanent repair.


The Golder study is the only longitudinal engineering study of its kind that examines the core reinstatement process over a ten year period

Proceedings of the International Gas Research Conference, 2014

A Cost Savings Strategy for Minimizing Pavement Restoration Costs



The cost of installing and maintaining underground utilities continues to increase. Pavement restoration costs can be reduced by as much as 80% by employing new and safer construction techniques such as the keyhole coring and reinstatement process developed and field proven over

20 years in the gas industry.


This paper identifies a core strategy for addressing the short-term issues of pavement failure related to utility excavations using solutions with long-term benefits. In doing so, it focuses on the need for highway agencies and municipal public work officials to provide and maintain a

smooth and safe road surface, while addressing assessment, inspection, and maintenance of utility infrastructures buried under the roads. As time goes on, more of the underground utility infrastructure reaches the end of its useful life, and more utility excavations will be required to

maintain and replace this aging infrastructure.

North American Society for Trenchless Technology (NASTT) NO-DIG, New Orleans, Louisiana 

Healing the Utility Cut: A Unique Coring and Pavement Restoration Process



E. Marshall Pollock, President & CEO, Utilicor Technologies Inc., Toronto, ON, Canada ABSTRACT: This paper discusses Utilicoring™, a unique pavement excavation and restoration technology. This technology was developed and field-proven over the last ten years by Enbridge Consumers Gas. This process facilitates utility access to underground plant and is a key cost-saving element in the growing utility maintenance trend to “keyhole” technology, which allows crews to cost-effectively perform repair or maintenance work on underground pipe or other buried plant from the road surface without resort to more costly, disruptive and inherently more dangerous excavation methods. It also has direct application to other utility service and trenchless operations including test holes and daylighting for directional drilling, inspection holes for pipeline integrity and subsurface utility engineering.

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