Maintaining pavement and increasing the life expectancy of a street may not seem like the most exciting topic, but it is a very important and essential city government function. As a city, we are always looking for new and innovative ways to deliver services — and maintaining Eden Prairie’s streets is a big part of that. There are two new areas of pavement management that are proving to be quite promising. One is a Texas underseal and the other is a fog seal.
First, I will start with the Texas underseal. On most of our city streets we perform the typical mill and overlay. This is when you mill up the current pavement on the road and then complete a new overlay. Within a few years a high percentage of cracks can reappear through the new overlay. When we perform a Texas underseal as part of a mill and overlay, only a small percentage of cracks reappear. Basically, a Texas underseal is when you mill a road, add a chip seal and then overlay. This new second step of adding the chip seal is rather minimal in cost, and does involve more coordination between contractors — but the final product is better.
Next is the fog seal. This is when you place a final layer of oil over a regular chip seal. Fog seals lock the chips in place which can get pulled out by plow operations and turning vehicles. This prolongs the benefit of a chip seal. Fog seals also reduce citizen complaints about loose chips in driveways and garages. It keeps chips out of the storm sewer system (and ultimately lakes, wetlands and creeks). The fog seal also protects the crack fill material from being pulled out and exposing cracks. Finally it looks nice and its black color absorbs heat in the winter helping reduce ice build-up. The fog seal also adds a little cost and causes some traffic disruptions, but the final product is also better.
Overall, the Texas underseal is doing a very good job of improving ride quality, reducing/eliminating reflective cracking and preventing water intrusion into the base. The fog seal locks in the chips, protects and camouflages crack fill material, further waterproofs the road and makes the road look brand new when done.
We believe that the minor added cost for both of these treatments will be greatly offset by the prolonged life we get from our overlays and chip seals. Early indications are that these new treatments will alter the reoccurring need to overlay and chip seal by several years (less disruption) and save the City more money in the long run.