Chip sealing is the most common preservation method in Spokane County. Chip Sealing is usually used to pave long stretches of rural roads, but has also been used on urban roads with success. Emulsified oil is applied to the road surface, with road chips added on top. There may be some minor delays during the application. This process helps seal the road and provides a new riding surface. To view a map of scheduled chip sealing routes, please visit: Chip Seal Status Map
What is a Chip Seal?
Chip Seals or seal coating, is the application of a protective wearing surface to an existing pavement.
Why chip seal the road?
To keep water from penetrating the road structure on paved surfaces.
- To fill and seal cracks and raveled surfaces of old pavement.
- To seal the pavement surface-minimizing the effects of aging.
- To provide a highly skid-resistant surface, particularly on wet pavements.
- The cost of chip seals is 15%-20% of the cost of pavement overlays.
What is the chip seal process?
- The road is prepped by fixing any small pavement discrepancies, crack sealed and then swept.
- An asphalt distributor is used to apply emulsion to the road. As the liquid asphalt meets the road surface, the water starts to evaporate.
- Immediately after spraying asphalt, a layer of crushed gravel is applied by a spreader. The gravel or (chips) size will vary depending on the road; from 1/4 inch to a maximum size of 1/2 inch.
- Next, the gravel is compacted and embedded into the asphalt by rubber-tired rollers. However, some gravel will not become embedded in the asphalt and is loose on the surface.
- The new chip-seal surface can require up to two days to set properly. Hot, dry weather helps speed up this process in which all of the remaining water in the emulsion evaporates and the asphalt hardens. Traffic can pass over this surface at reduced speeds during the curing process.
- After curing, the loose gravel is swept off the surface, and the road striped if applicable.
As with any road construction project, motorists must exercise caution. Reduced speeds ensure your safety and minimize the chance of damaging your vehicle.
During the chip seal process, from the time the gravel is placed on the road to when the excess is swept away, the speed limit is 25 mph. At that speed, vehicles should not be damaged by flying rocks.
Traffic moving at higher speeds can create dust, limit visibility, and cause an inconvenience to local residents. Increased speeds can also cause gravel to break loose from a fresh chip seal creating the risk of flying rock. Rocks thrown from your tires may crack or break a windshield. Flying rocks might also injure pedestrians, bicycle riders, or motorcyclists.