Pothole repair for commercial parking lots

Pothole repair replaces failed asphalt with compacted patching material so the surface is level, sealed against water and safe to use. The Federal Highway Administration (FHWA) manual of practice on pothole repair (FHWA-RD-99-168) describes a pothole as localized distress where the asphalt surface breaks up and traffic carries the loose pieces away. It names moisture, freeze-thaw action, traffic and poor underlying support as the usual causes. The Indian Health Service calls water the most common and significant cause of pavement deterioration and describes potholes as a severe form of fatigue cracking, which is why open cracks and poor drainage are treated as early warnings.

The FHWA manual covers four repair methods:

1. Throw-and-roll. Cold mix is placed in the hole and compacted with truck tires, leaving a slight crown of about 3 to 6 mm. The manual prefers it to throw-and-go, where material is left for traffic to compact.
2. Semi-permanent. Water and debris are removed, the edges are cut back until the sides are vertical in sound pavement, and the mix is placed and compacted with a plate compactor or small roller. The manual ranks it among the best methods short of full-depth replacement.
3. Spray injection. Water and debris are blown out, a tack coat of binder is sprayed on the sides and bottom, and asphalt and aggregate are blown in and covered with a layer of aggregate.
4. Edge seal. A throw-and-roll patch is later sealed along its edges with a tack ribbon and sand, which the manual says can improve performance in older, heavily cracked pavement.

The manual describes hot mix asphalt as a preferred alternative for patching, although its own procedures cover cold mix. Where the pavement has failed deeper than the surface, sealcoating guidance from the Pavement Coatings Technology Council (PCTC) and the Colorado Asphalt Pavement Association (CAPA) calls for removing damaged pavement to the full depth of the damage and replacing it with new asphalt. Recurring potholes in the same area usually point to base or drainage problems that call for parking lot repair rather than another patch.

Most potholes start as cracks that let water reach the base. Planned inspection and crack sealing find them early, cut emergency patch calls and trip claims, and leave a dated record of each hazard and repair.

The authority having jurisdiction, the manufacturer and the property’s insurer can require more frequent service, and each location’s schedule is set in its program and recorded on every visit.

• Date and source of each report, with photos and a marked site plan
• Size, depth and location of each pothole, and whether it was in an accessible space or route
• When and how the hazard was guarded until repair
• Repair method and material, with the safety data sheet for cold mix
• Weather, and whether the patch is temporary or permanent
• Before and after photos and the provider’s sign-off
• Follow-up inspections showing whether each patch held

• Number, size and depth of the potholes
• Repair method: cold-mix patch, semi-permanent repair or full-depth replacement
• Choice of hot mix or cold mix, and the season the work is done
• Base or drainage failure under the pothole
• Traffic control, closures and phasing to keep the lot open
• Night, weekend or emergency scheduling
• Restriping of stalls or markings disturbed by the repair

The FHWA manual notes that material is usually one of the smallest parts of a patching operation’s cost, and that longer-lasting materials can reduce the cost of repeat repairs.

• Asphalt, Concrete and Parking Lots
• Parking Lot Repair
• Sealcoating