Roadway Chip Seal

Chip Spreader

Chip Seal Program

Chip Seal (also called seal coating, or Bituminous Surface Treatment) is the application of a special protective wearing surface to an existing pavement.

This program has substantial benefits for local roadways and the drivers who use them, including: 

  • Improves safety and creates a highly skid-resistant surface.
  • Saves money and is substantially less expensive than asphalt overlay. 
  • Extends the life of pavement.
  • Waterproofs the surface. 
  • Prevents potholes and seals cracks, keeping water from seeping into the roadway structure. 
  • Chip Seal acts as a key to many M&O maintenance activities.    

Slow Down and Expect Delays

Drivers should plan to use alternate routes during project work and expect delays. Speed limits will be lowered to 25mph in work zones, and the Whatcom County Sheriff’s Office will have extra emphasis patrols to ensure safety. Remember that traffic fines double in work zones. 

Road delays are never an enjoyable part of summer driving, and we appreciate the patience of the driving public during this process. This work will last several months, but the benefits will last for decades. 

The Chip Seal Process 

  1. First, asphalt is mixed with about 30% water. This emulsified mixture is then applied to the road using a special spray truck. As soon as the liquid asphalt meets the road surface, the water starts to evaporate.
  2. Immediately after spraying this asphalt, a layer of crushed gravel is applied by a spreader. The gravel (or chips) have a maximum size of 3/8 inch.
  3. Next, the gravel is compacted and embedded into the asphalt by rubber-tired rollers. However, even with high pressure rolling, some gravel will not become embedded in the asphalt.
  4. The new chip-seal surface can require up to two days to cure 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.
  5. After curing, the loose gravel is swept off the surface. This may take several sweepings.

We Appreciate Your Patience

Please be patient when traveling in work zones. Traveling at the posted construction speed limit in construction zones will ensure your safety and the safety of highway workers. It is also the law. Traffic fines are doubled in construction zones. Obeying warning signs and flagging personnel instructions benefits all those who share the roadway with you too.

  • View/print an informational flyer explaining the Chip Seal Program. 

Contact Us


    Monday - Friday 8:00 am to 4:00 pm

    (360) 778-6400

    Ask a Question or Report a Problem

    901 W. Smith Road

    Bellingham, WA  98226

    Andy Bowler, Superintendent

    Gina Miller, Assistant Superintendent

    Michael Koenen, Assistant Superintendent

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