2019 Overlay/Chip Seal Street Program

The City utilizes three preventative maintenance procedures each year. This consists of a crack seal, a chip seal and an overlay. Each of these processes help to mitigate the deterioration of our City streets.

Asphalt Over Time

As asphalt pavement progresses through its performance life cycle, its appearance diminishes over time. Fine hairline cracks spread and deepen within the asphalt. Without ongoing maintenance, water may enter through cracks and holes may form, undermining the substrate. In this case, the most effective form of repair is to remove and replace the deteriorated area.

As soon as freshly laid hot asphalt pavement mix begins to cool, the aging process begins.
When oxygen in the air and water combine with asphaltic binder of the pavement, a chemical change takes place. At first, this process is necessary for the pavement to become hard and firm. Later, if this process is not arrested, a complete deterioration of the asphaltic binder will take place and reduce the pavement to a layer of loose stone.

The following items contribute to the deterioration of asphalt:
  • Gas
  • Hot or cold weather
  • Oil
  • Salt
  • Sun oxidation
  • Water penetration

2019 Overlay

This year we will be working on 32nd St W, King Ave W and S. 20th St W
Update: Coming Soon
The overlay process replaces existing deteriorated asphalt surfaces with new asphalt. Generally, the top two inches are milled off as a first step. Once this layer has been removed any exposed problem areas are removed and replaced in a dig-out process. The surface is then prepared and a new two inches of asphalt is put in place. (See link to the right for map)

2019 Chip Seal 

Update: There will be no Chip Seal project for 2019. Instead, we will be patching failed areas of asphalt in preparation for a 2020 Chip Seal.
Click here for a location of work map

How are 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 the opportunity to maintain the roads for very low cost.
  2. A chip seal is about one tenth 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 enhance safety by providing good skid resistance.
  6. Chip seals provide an effective moisture barrier for the underlying pavement against water intrusion by sealing cracks in the pavement.
  7. Chip seals prevent deterioration of the asphalt surface from the effects of aging and oxidation due to water and sun.
How Are Chip Seals Placed?
First, the road surface needs to be properly cleaned of debris and any holes patched. Next, an asphalt distributor truck starts by spraying each lane with hot liquid asphalt to assure an even application. The asphalt used is applied at a temperature between 150 and 185 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, a rubber-tire roller is used to 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.