Potholes - how they're formed, how they're filled

Public Works recently shared information on the popular subject of potholes:

See a pothole? Call or email 311 ([email protected])

Following the rain and the record breaking temperature on Sunday, the Roads and Parking Services team have sprung into action to address what is inevitable with this type of weather pattern, pothole repairs. We will be taking advantage of the mild weather expected over the next few days by redirecting additional resources and deploying more crews to fill potholes.

Since January, Ottawa has seen all sorts of weather – everything from a record snowfall, prolonged freezing rain, temperatures above zero, rain, flash freeze and then more snow. We know this winter season will wreak havoc on our roads, sidewalks and winter cycling network as the freeze / thaw cycles take hold this month, bringing with it an increased number of potholes. We are on the job and ready!  

How are Potholes Formed?

Potholes are formed when water (from rain or melted snow and ice) seeps into small cracks or holes in the road. As temperatures drop, the water under the road freezes and expands pushing up on the road above, creating larger cracks – when the temperature rises above zero, the water evaporates and leaves an open space under the road. The weight of cars and trucks travelling over these weak spots breaks the asphalt, resulting in potholes. 

How do we Repair Potholes?

Potholes are filled by cleaning the hole of debris and water, then packing it with asphalt and rolling or pounding it down. At this time of year, some potholes in high traffic areas may need to be refilled more than once. This happens because water works its way back into the hole preventing the asphalt from forming an adhesive bond with the pavement.

Filling Potholes in Winter 

In winter, conditions are not ideal for pothole repairs. The unstable conditions, including ice and water in the holes, as well as the cold temperatures and frequent freeze / thaw cycles, prevents the patch from adhering as well to the roadway making the repair temporary. Products that staff use to repair potholes during the winter months are Cold Patch and Warm Mix asphalt.

Cold Patch asphalt is a blended asphalt material which can be stored for extended periods of time. It can be used in all temperatures, does not require special equipment to compact and can be applied directly to the roadway without heating.

Warm Mix asphalt can be used year-round and produced at a lower temperature using different adhesives in the mix. Once the material is heated, the adhesives become thinner allowing improved workability and flow. The material can be manually compacted with a tamper, or shaped and compacted with power plate tampers or rollers.

What’s Next? 

Based on the forecast, we are anticipating several freeze-thaw cycles over the next few weeks. Residents can expect to see our pothole crews across the City as we begin some of our spring road maintenance operations. Ottawa winter’s are hard on our infrastructure, and this year in particular, we are anticipating an increased number of potholes. We appreciate your patience as we complete our operations.

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Address: 110 Laurier Ave W, Ottawa, ON K1P 1J1