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ITD from the Vault: 1990

Crews begin work on "the wall"

Concrete panels faced with rock and pebbles are hoisted by crane into the air and gently placed into position by human hands while fill dirt is pushed over wire racks nearby.

This is the scene at the 27th Street extension and overpass as workers scramble to help build "the wall."

"The wall" is designed to support not only itself but several hundred thousand pounds of fill material too.

This work and the mechanically stabilized retaining wall are being built this spring as part of The Connector project.

"Building this wall is saving a considerable amount of right-of-way," said Steve Hutchinson, assistant District 3 engineer. "Because the wall is vertical it saves space in an urban area where right-of-way costs are expensive."

Designers worked with business owners who will be neighbors with the wall and came up with an exposed aggregate finish for the outer surface of the panels to make the wall more aesthetically pleasing.

"Without the rock finish, it would probably have to be painted which would mean higher maintenance costs," Hutchinson said. "This design is more pleasing to the eye and is less costly to build than a conventionally built retaining wall where the concrete is poured in place."

A sub-contractors' crews are building about 40 concrete panels a day in Boise. Once the panels have cured to reach a strength of 4,000 pounds per square inch, they are taken to the construction area. Layers of fill dirt are placed and compacted between sections of wire mesh that hook onto the concrete panels. This provides the support that holds the wall in place.

Upon completion in May, more than 2,000 panels spanning more than 2,270 feet, will make up the wall that reaches from ground level to 32 feet high in places. The wall will be part of the 27th Street overpass which will carry east and westbound traffic on The Connector. Traffic underneath the overpass will be traveling on the 27th Street extension from Fairview Avenue to Shoreline Drive.

The Connector is a $60 million project being built jointly by the Idaho Transportation Department and the Ada County Highway District. Final completion of the entire project, designed to improve east-west traffic flow, is set for 1992.