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Common keyhole methods involve creating a pavement opening only 12 to 18 inches in diameter, usually made with a circular core-hole cutter, allowing for remote access to the facilities. Restoration is accomplished by replacing the cored pavement coupon after repairs are made.


Once the core has been cut and removed, vacuum excavation equipment is used to excavate down to the pipe. Debris removed from the hole is stored in a tank on the vacuum truck, and, ideally, the debris can be re-used to backfill the keyhole. Vacuum excavation is defined as a means of soil extraction through vacuum when using water or air jet devices for breaking the ground. This method of excavation is commonly referred to as “soft excavation” and is commonly accepted as being equivalent to hand digging within the “tolerance zone” around underground facilities.


With the help of specialized, long-handled tools, various utility operations can be conducted through a keyhole opening. These activities currently include: potholing/depth checks, valve box cleanouts, meter guard installations, plastic pipe squeeze-offs, service installation and abandonment, cathodic protection, and cast-iron joint sealing.


Backfill and soil compaction are integral to the effective replacement of the cut core. Using the proper materials during backfill and core replacement will prolong the life of the pavement. After proper backfilling the keyhole core that was originally cut from the pavement is reinstated back as a permanent restoration of the roadway using special bonding products. Site restoration requires no temporary patching, overnight road plating, or return trips to make final restorations. The road is restored to traffic-bearing strength in as little as 30 minutes following job completion.