Chicago Keyhole Standard


NEW (January 2014) Rules and Regulations for Construction in the Right of Way in Chicago recognize and approve Keyhole Coring and Reinstatement.










In January 2014, Section 4.1.10 of the Rules and Regulations for Construction in the Public Way of the City of Chicago, specifically recognizes and approves keyhole coring and reinstatement for subsurface utility investigation or facility leak detection or repair in city streets. In doing so, the Regulation exempts keyhole coring that follows the guidelines from the more rigorous and complex conventional pavement restoration requirements that include full pavement restoration from curb to centreline or to the nearest horizontal or tranvesrse joint, milling and overlay with hot mix asphalt and full perimeter sealing.


The coring guidelines specify that the pavement core shall not exceed 18 inches in diameter and shall have a center hole drilled through the pavement so that it can be lifted out and replaced in its entirety when work is complete. The soft material shall be removed using vacuum excavation as required. Upon completion of utility work, suitable salvaged backfill material (or appropriate replacement aggregate or flowable fill) and new sand shall be placed back in the hole and compacted in one foot lifts using a tamping rod up to about one inch below the core bottom. The final inch of backfill shall be replaced with pea gravel. The hole shall be filled with a bonding compound, Utilibond or equivalent material. Then the pavement core shall be leveled in place leaving a smooth paved surface. After the bonding compound sets, the surrounding pavement shall be cleaned of all debris and excess grout. Grout material to be used must be Utilibond or other similar grout material approved by the Commissioner. The keyhole technology means and methods shall permit normal vehicular traffic to resume over the restored keyhole location within 30 to 45 minutes of the completed repair.