Pottawattamie County utilizes seal coat roads to provide dust free gravel roads. Majority of these roads have been paid for by the residents that reside on that road and have been maintained by the County ever since.
Since the roads are gravel they are less stable than traditional paving. Due to the work being paid for by the residents utilizing special assessment they were constructed with the lowest cost method deemed acceptable. The roads are seal coat with an 8” deep stabilized gravel base.
Given the long history of these roads and the 10-12 year service life; many people are unfamiliar with the work to repair them. The process begins by recycling the surface and base into a new base. This may take several passes with a reclaimer to depth of 8”; but the final pass may include adding more asphalt emulsion. The recycled material is then reshaped by motor graders and compacted. The color of the material is similar to dirt due to the color of the asphalt oil, it can be alarming but functions well if compacted before getting rained on.
After the base is repaired, shaped, and compacted the asphalt emulsion is allowed to remain open so any water may evaporate and help harden the base. Once dry (usually indicated by a “darkening” of the surface) asphalt emulsion is sprayed on the surface to seal out water. The asphalt emulsion is then covered with chips to protect it from damage and cars from getting asphalt on them. We may double seal the surface or single seal the surface depending on conditions. We leave the loose chips on the surface to protect traffic from the “tar” usually through the rest of the summer season. It looks like a gravel road, but the intent was originally suppress the dust and the dust should be nearly nonexistent at this point. Normally by the following spring the road is free of loose material and the road is color of the aggregate used. Some people don’t like the color of the gravel, but when it becomes the color of the asphalt then we’ve lost our wearing surface and seal and the road will fail.
We understand it can be a frustrating and messy project; please be patient with the crews and workers they want to do the best they can and it is a tough job.
If you are interested in upgrading your gravel road please review the policy on the Secondary Roads website.