1/19/2012
ITD continues investigation of failing micro-seal on Idaho 75 section in Wood River area
KETCHUM – The Idaho Transportation Department continues to investigate the recent failure of a micro-seal project between Hailey and Ketchum. The portion of roadway between East Fork Road and the Big Wood River bridge near St. Luke’s Wood River was resurfaced in early- to mid-September. The micro-seal failed to adhere to the asphalt surface.
ITD is working with the contractor of the project, Knife River Northwest Inc. of Boise, the subcontractor that applied the product, Valley Slurry Seal of Sacramento, Calif., and industry experts from the International Slurry Surfacing Association (ISSA) to determine the probable cause of the failure.
ITD has received guidance from the ISSA which has been the basis for the micro-seal application specifications. By utilizing these same resources, ITD hopes to find ways to improve the product so its use can continue.
“In order to be innovative, ITD relies on its partners in the private industry to provide new products and technologies that help improve convenience to the traveling public,” project engineer Scot Stacey said.
A micro-seal is comparable to a seal coat but is premixed and applied as a slurry. The micro-seal is often used in higher-traffic areas in place of a seal coat, intended to protect and extend pavement life and provide improved vehicle traction.
In the recent resurfacing project, the contractor completed a scrub coat prior to applying the micro-seal. The scrub coat is a liquid asphalt and sand mixture to fill holes and ruts in the road’s surface but has not been affected by the micro-seal failure.
The micro-seal treatment has been applied between Hailey and Ketchum without failure in the past. Additional application of the micro-seal is scheduled to be take place on the remainder of the Hailey to Ketchum project later this year.
ITD did approve the mix design of the micro-seal prior to its application and the contractor did pass its quality control tests at the time of application.
“ITD wants to ensure the citizens of Idaho that we take our role as stewards of taxpayer money very seriously,” Stacey said. “ITD will take appropriate action based on the findings of our ongoing investigation.”