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Summer maintenance work extends lifespan of Treasure Valley bridges

ITD is using a process called hydrodemolition to maintain and extend the lives of several bridges throughout the Treasure Valley. Hydrodemolition involves removing concrete from the surface of a bridge by using a high-powered pressure-washer. The bridge is then resurfaced with a silica fume overlay, which requires the concrete to set up, or "cure," over multiple days.

Click here for a video of hydrodemolition performed in April during maintenance on the Orchard Street Bridge over the I-184 Connector.

"Periodic bridge maintenance allows ITD to maximize our transportation dollars," said ITD's Jennifer Gonzalez. "When a bridge undergoes hydrodemolition, it gives motorists a new driving surface and protects the bridge from water damage for many years to come."

Over time, bridges begin to show signs of wear from traffic loads, rain and snow, and road salt. These elements often cause tiny "micro" cracks in the surface. Left untreated, water and salt can seep into the cracks and cause the rebar and railings to rust. Hydrodemolition prolongs the lifespan of a bridge surface by up to 20 years.

The process involves first pressure-washing a bridge at about 20,000 psi, or pounds per square inch.

"To give you an idea of how powerful this is, in comparison, a home pressure washer is probably around 1,300 to 2,000 psi. The pressure-washing process turns the top inch or so of concrete into tiny pieces of gravel. The next steps are for crews to sweep the gravel off the bridge, clean the bridge, and then lay on a thin layer of new pavement," Gonzalez said.

On May 18, crews used hydrodemolition to resurface and waterproof the deck of the westbound Interstate 84 railroad bridge at the Gowen Interchange. Work on the I-84 railroad bridge is part of ITD's project to replace the Gowen Interchange and widen I-84 to three lanes in each direction between Broadway Avenue and Gowen Road.

ITD inspects its bridges each year and notes which bridges are due for routine maintenance.