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Potholes 101

Updated: 05/25/2018

We all hate potholes - sometimes even driving out of our way to miss the biggest ones. But here in Minnesota, they seem to be a fact of life.

A pothole is a type of failure in asphalt pavement caused by the presence of water in the underlying soil structure and traffic passing over the affected area.

Skidloader patching pothole on Gorman StreetThe introduction of water to the underlying soil structure first weakens the supporting soil. Traffic then fatigues and breaks the poorly supported asphalt surface in the affected area. Continued traffic ejects both asphalt and the underlying soil material to create a hole in the pavement.

In the winter, when melting occurs during the day and refreezing at night, this can increase the number of potholes. The water will expand as it freezes, pushing the asphalt up. After several times, the asphalt will crack and pop out causing the pothole to form.

Pothole patching methods fall into two distinct categories: temporary and semi-permanent. Temporary patching is reserved for winter weather conditions that are not favorable for a permanent solution. It usually includes using a cold mix asphalt patching compound to temporarily restore pavement smoothness.

Crews adding new bituminous to fill potholeSemi-permanent patching uses more care in reconstructing the perimeter of the failed area to blend with the surrounding pavement. It usually uses a hot-mix asphalt fill. A pothole could be also milled out and cleaned. Crews then apply tack oil to bond old asphalt to the new asphalt and fill with a hot mix asphalt and compact, making the road smooth again. 

Unfortunately, fixing potholes is a regular part of street maintenance, especially in cold-weather climates. We do our best to keep city streets as smooth as possible, but Mother Nature and traffic always seem to be working against us.

Need to report a pothole?