Idaho highway project used recycled glass but faced high costs

In 2002, the state of Idaho implemented an experimental recycling project by incorporating hundreds of tons of discarded glass into the construction of a section of State Highway 75 near Ketchum. The glass was placed in a layer between 20 and 30 centimeters thick, buried deep beneath approximately 1.2 meters of fill material, stone, and asphalt.

The initiative was proposed by State Senator Clint Stennett to utilize glass accumulated at the Ohio Gulch recycling center. According to the Federal Highway Administration, crushed glass can function similarly to sand if particles are smaller than 4.75 millimeters and are combined with coarser materials to meet compaction and drainage specifications.

Despite the technical viability, the project highlighted significant economic hurdles. Engineers noted that the process of collecting, separating, and preparing the glass made it considerably more expensive than using local granular materials or gravel. The high costs associated with the treatment and processing of recycled glass remain a primary obstacle to its widespread use in infrastructure.