Two for the price of one...
Crews complete twin-killing
of Robinson, Black Cat bridges in one night
A big, and necessary, step in the eventual expansion of Interstate 84 between the Garrity Interchange in Nampa and the Meridian Interchanges occurred with a crash Friday (Sept. 26) when crews demolished both the Robinson Boulevard and Black Cat Road bridges over the freeway.
Initially, only Robinson was scheduled to be removed Friday night; Black Cat was to come down the following night. That would have required two separate nine-hour I-84 closures. However, the work was accomplished in one night to maximize public convenience. A few extra excavators and additional equipment were brought in to accomplish the feat.
'We received a proposal late Friday to mobilize additional equipment and accomplish both operations in one night. The result is safety and convenience for motorists and surrounding residents.'
Region 3 Engineer
Excavators equipped with hydraulic breakers – similar to jackhammers – pounded on the bridge deck of the two overpasses until the deck and girders broke and fell away. A 12-inch sand mat covered the interstate underneath to cushion the fall and protect the roadway surface. Pieces of the overpass were transported to a local disposal site off McDermott Road; Thueson Construction owns the site.
"We received a proposal late Friday to mobilize additional equipment and accomplish both operations in one night," said Region 3 Engineer Shawna King. "The result is safety and convenience for motorists and surrounding residents." And fewer interruptions to interstate traffic.
The demolition began just after 11 p.m. Both bridges were down and the interstate reopened as planned by about 7:15 the next morning.
The dual bridge demolition was the first step in a four-month project to reconstruct both overpasses while new lanes are constructed on I-84. Using traditional methods, bridge replacement would have taken from a year to 18 months.
However, a new method using a SPMT (Self-propelled Modular Transport) will be used, which allows most of construction on the new 400-ton spans to be done just off-site, then moved into place. The multi-wheeled computer-controlled SPMT only travels about one mile an hour, but can spin 360 degrees and is accurate to within centimeters.
SPMT has been used a handful of times for bridge replacement in the West, most recently in Utah on the 4500 South Bridge over I-215 in Salt Lake City, and a few years ago to replace the bridge connecting Washington to Oregon over the Columbia River. Florida, Louisiana and Rhode Island DOTs also have used the technology since 2006.
The $8.5 million project to replace the bridges at Black Cat and Robinson should be completed by late January.
"Reconstructing both bridges at the same time allows us to greatly expedite the I-84 widening project," said ITD District 3 Engineer Dave Jones. "This project is crucial to relieving congestion in the valley."
Graham Construction and Management of Spokane is the contractor for the project that takes advantage of GARVEE (Grant Anticipation Revenue Vehicle) bonds to expedite critically needed projects in six Idaho corridors.
Nampa mayor Tom Dale and Senate Transportation Committee Chairman John McGee from Caldwell were on hand for Friday’s demolition event, and McGee used the platform to sing the praises of the GARVEE program and transportation in general.
“You’re seeing the GARVEE program at work here”, McGee said. ”It is exciting to see the modernization of transportation in the valley.
“For years now, we’ve been in traffic jams as we head to work and traffic jams as we head home. It’s hurting our environment and our quality of life. This is an exciting day for the Treasure Valley.”
Dale agreed, saying, “It really means another step in the process. This is a big step in the completion of the project.”