Gravel Chip Spreader

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Spot Oil Application

Finishing Touches

Chip Seal Fact Sheet

“Chip Sealing” is a common pavement maintenance practice that extends pavement life and provides a good driving surface.  Mason County is responsible for the maintenance of 620 miles of roadway. Of that there are approximately 370 of road miles maintained with BST-Bituminous Surface Treatment (Commonly referred to as chip seal).

The chip seal will last an average of seven years, which will vary with the type and amount of daily traffic. The candidate roads are reviewed annually for condition, and added to the chip seal program if warranted. We typically work on road’s county wide.

The Fact sheet is to provide the residents of Mason County information about the chip seal program by answering some of the frequently asked questions.

How is Chip Seals Different from Asphalt Overlays?

The difference is in the construction method.  Hot Mix Asphalt pavement is produced by heating liquid asphalt and mixing it with aggregate, with the mix then spread and compacted to form a durable road structure and riding surface.  Chip Sealing uses the same ingredients as asphalt concrete paving, but the construction method is different.  With chip seals, a thin film of heated asphalt liquid is sprayed on the road surface, followed by the placement of small aggregates ("chips").  The chips are then compacted to orient the chips for maximum adherence to the asphalt, and excess stone is swept from the surface.  The ingredients of hot mix asphalt and chip seals are the same; only the construction methods are different.

Why Use Chip Seals?

  1. Chip seals provide Mason County Public Works (MCPW) with the opportunity to maintain the roads for very low cost.
  2. A chip seal is about one fourth to one fifth the cost of a conventional asphalt overlay.
  3. By extending the time between asphalt overlays, chip seals result in lower costs over the long term.
  4. By placing a chip seal sooner than an asphalt overlay would be placed, the traveling public benefits from roads maintained in better condition.
  5. Chip Seals eliminate the need to crack seal.
  6. Chip seals enhance safety by providing good skid resistance.
  7. Chip seals provide an effective moisture barrier for the underlying pavement against water intrusion by sealing cracks in the pavement.
  8. Chip seals prevent deterioration of the asphalt surface from the effects of aging and oxidation due to water and sun.
  9. In hot weather, chip seals re-seal cracks by flowing back together.

What steps are involved in Chip Seals?

The year prior, the roadway is pre-leveled to eradicate the deficiencies in the roadway. The next process to the chips seal program, start with properly cleaning the road surface sweeping debris and patching holes. Once prep-work is completed, county crews averaging 19 employees start application. An asphalt distributor truck starts by spraying one lane with hot liquid asphalt to assure an even application.  The asphalt used is applied at a temperature of approximately 190 degrees Fahrenheit.  A chip spreader follows as rapidly as possible with a rock application, preferably within one minute.  The asphalt must be fluid so the rock will be embedded by the displacement of the asphalt.  The rocks are an aggregate crushed to a special specification for size and cleanliness.  Next, two pneumatic rollers set the rock into the liquid asphalt.  Rolling orients the flat sides of the rock down and produces a tighter chip seal.  It takes two to four passes of the roller to set the rock. 

Two or three days after the application, the road is watered, excess rock is swept from the surface, warning signs are removed, and speed limit is re-established. Permanent road striping is redone before the end of the season.


What issues affect a quality chip seal application?

Since a roadway is rarely closed to traffic for the chip seal application, a smooth flow of traffic through the work area is required. Driving slowly, not turning sharply, braking quickly or tire spinning is crucial for the fresh chip seal not to be disturbed.


Until a road is broomed, the lowered speed limit needs to be observed so chip rock isn’t dislodged, and passing vehicles aren’t damaged by “flying” chip rock. 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. By driving 25 mph, you protect your vehicle from unnecessary damage that can be caused by the sprayed asphalt and loose gravel. The slower speed also decreases the chance of damage from rocks which may be thrown up from other vehicles.

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

The chip seal operation is supported by the Mason County Sheriff’s Department Road Deputies, who ensure the lowered speed limits are being observed.

Please be patient. Traveling at the posted construction speed limit in construction zones will ensure your safety and the safety of the county road crews. It's 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.


The chip seal operation is supported by the Mason County Sheriff’s Department Road Deputies, who ensure the lowered speed limits are being observed.


What does it cost?

A mile of chip seal costs Mason County about $32,000, compared to $250,000 + per mile for asphalt overlay, it is very a cost effective program.

Who does the work ?

The chip seal program is done by Mason County Road Operation & Maintenance employees. The only element contracted out is striping that may need to be redone, and the manufacturing and delivery of chip rock to various stock pile sites.

When is the work done ?

The chip seal program usually starts after July 4 th and completed by early to mid August. We also do work for the City of Shelton. Check the County website under Public Works Road Maintenance to see where crews are chip sealing each week or to get a list of roads to be chip sealed for the year.