Home | Case Studies | Supporting Nicor Gas Efforts

The Situation
In recent years, utility companies across the country have realized significant time and cost savings through the use of keyhole coring and reinstatement, a trenchless technique that enables crews to make repairs through small openings (12″ to 18″ in diameter) in the pavement and using debris removed from the hole to backfill the keyhole.

Many U.S. gas utilities have embraced the process and are working with their respective jurisdictions to gain approval and acceptance. Recently, GTI worked with Nicor Gas, one of the country’s largest gas distribution companies serving more than two million customers in northern Illinois, to gain approval from the Illinois Department of Transportation (IDOT) for use of the keyhole coring and reinstatement procedure for underground repairs.

The Technology
Coring and reinstatement offers many advantages compared with traditional pavement cuts. Often compared with microsurgery in the healthcare industry, keyhole coring or “keyholing” is a process in which a core is cut in the roadway pavement to access buried utilities, for locating purposes or inspection, or to use specialized tools for performing repair, maintenance, or installation.

Vacuum excavation is used to access the pipe. Debris removed from the hole and stored in a tank can often be reused to backfill the keyhole. The previously cut pavement core (or coupon) is restored with bonding material after repairs are made.

Utility operations and the communities they serve can realize substantial benefits through the use of this process, including: less traffic delays and disruption, minimal damage to roads, a reduced environmental impact, quicker repairs to underground utilities, and improved worker safety and productivity.

The Challenge
Nicor Gas has been a regional leader in the adoption of keyhole technology since 2001 and has been using the keyhole coring and reinstatement process in its underground repair work for years. For many years, Nicor engineers have worked to gain official approval from IDOT for use of the process.

An Opportunity for State Approval
In early 2008, at the invitation of Nicor Gas Senior Manager, Keith Griffin, an IDOT representative visited a number of project sites, including a gas main installation site on Higgins Road (Route 72) in Pingree Grove, Illinois. The IDOT representative compared conventional pavement openings with openings that had been sealed through the keyhole core reinstatement process. “The conventional openings were failing – the patches were worn,” he said. “The cores were holding up pretty well.”

“This is a significant achievement for us and should lead to improved relations and approval of core reinstatement acceptance with local jurisdictions.” Bart Hill Senior Manager, Technical Support Nicor Gas

GTI and IDOT
With its proven 10-year track record of developing engineering reports and test data, GTI is helping utilities like Nicor Gas gain quick approval for the keyhole coring and reinstatement process from municipalities and other highway authorities and departments of transportation.

Following the inspections by IDOT of the Nicor Gas projects in 2008, Nicor Gas submitted research analyses and testing documentation supplied by GTI on the coring reinstatement process and bonding agents to IDOT. That documentation was then forwarded to the IDOT Materials Department in Springfield, Illinois.

A document entitled “Technical Reference for the Reinstatement of Keyhole Cores: A Synthesis of Testing Programs and Procedures” prepared by GTI provided in-depth testing information about the process, as well as:

• Research and testing programs conducted with various agencies to evaluate the performance of various materials used for bonding the reinstated cores to the intact surrounding pavement under loads
• Laboratory tests performed at the University of Illinois to evaluate the strength of several bonding materials
• Field stress tests conducted with an Accelerated pavement Loading Machine (APLM), as well as tests performed by the National Research Council of Canada and the U.S. Army Corps of Engineers on reinstated cores.

Outcomes and Next Steps
In October, 2008, IDOT issued its formal approval for keyhole coring and reinstatement on state right-of-ways. Once additional tests are completed, it is anticipated that Utilibond, the bonding agent manufac¬tured by Utilicor, will be added to the approved materials list for the coring and reinstatement process.

The Future
With the support of GTI, gas utilities, major keyhole vendors, and other partners, many jurisdictions have already approved the use of coring and replacement of the core as a permanent paving technique. GTI continues to work to advance acceptance of the process, as the nation’s infrastructure continues to age.

About GTI
Based in the Chicago area, GTI has been meeting the nation's energy and environmental challenges for more than 65 years by developing technology-based solutions for consumers, industry, and government.