Challenge 4: Environmental Concerns. Half of the job included work around the water shed reservoir that supplies drinking water to area residents. All mill tailings had to be cleaned from the road each day to prevent water contamination. Micro surfacing is a green product and is environmentally safe, but letting it get into the area drinking water was not an option.
Parley's Canyon draws a lot of pop-up rain showers, so the crew watched the weather constantly to ensure the rain didn't wash anything into the reservoir. In addition, as a highly travelled road, the crew made sure everything looked professional to the public so they knew the drinking water would be kept safe.
Preserving I-80 for the long haul
The Parley's Canyon section of I-80 is steep with eight percent grades, windy and has limited visibility at night. The project was also unique because the micro surfacing treatment was put on top of a milled asphalt surface. In most cases, it is laid over the existing asphalt.
Micro surfacing mixtures use four main ingredients, including a polymer-modified emulsion that produces a chemical reaction to force the moisture out and allows it to set in less than an hour -- so traffic can return quickly. In total, Intermountain Slurry Seal used approximately:
- 16,000 tons of Type III aggregate
- 1,850 tons of polymer-modified emulsion
- 80 tons of Portland cement
- 300,000 gallons of water
Due to the environmental restrictions, all of the materials had to be stored at one end of job. Each day, Bergkamp's M1 was first loaded with all of the necessary materials at the stockpile site. Then four Bergkamp mobile support units and three Flow Boy support units were loaded with material and stationed at specific intervals in front of the continuous paver. As the paver ran out of material, a support unit slowly backed up to the paver, connected and transferred materials so it could keep running. Those support units then went back to stockpile and refilled.
"This process reduces the number of construction joints, or bumps, in the final surface," said Price. "We also used Bergkamp's variable width spreader box to adjust to varying pavement widths and prevent overlap and gaps. Combined with a continuous paver, this makes the road smooth and consistent for easy driving."
To ensure a smooth and long-lasting surface, Intermountain Slurry Seal put the micro surfacing treatment down in two layers. The first layer was used as a scratch coat to smooth and level the milled road. It was applied thicker at about 27 pounds per square yard. The second coat was applied as the final driving finish to provide improved skid resistance and protection against the extreme weather conditions. It was applied at 25 pounds per square yard.
"When micro surfacing east, we had a traffic control plan where the heavier trucks ran on the right shoulder and the other vehicles ran in the normal right lane," said Price. "This allowed us to work in two lanes at one time and still meet the UDOT's requirements. When going west, there wasn't enough room to do this so we had to perform most of the micro surfacing in one-lane increments and the center lane at night. "With this micro surfacing treatment, I am confident it will hold up better and won't delaminate from the pavement because it keeps precipitation out."
A favorable outcome
Mayhew drives the route every day to work and says the results have been favorable. "Last winter we only observed about seven total potholes going both east and west," said Mayhew. "And honestly, those had more to do with the underlying asphalt surface that failed than the micro surfacing. With the OGSC, we had more than 700 potholes per year for the last two years. The micro surfacing treatment has held up well and doesn't have the cracking that we saw with the previous treatment."
New Technology Aids Intermountain's Future
Intermountain Slurry Seal's equipment arsenal includes Bergkamp's new M1E continuous paver, which was used to help complement the original M1 unit's preservation of I-80. The difference between the two units is that the M1E uses the EMCAD (Electronic Mix Control And Diagnostic) System to simplify maintenance and calibration and help the owner or operator better monitor production rates and costs.