Crews are installing precast bridge girders and pouring a new bridge deck for the Historic Route 66 Rio de Flag bridge project.

The Rio de Flag Flood Control Project is a 20-year effort between the city of Flagstaff and the U.S. Army Corps of Engineers to prevent life/safety hazards and property damage caused by significant flood events in Flagstaff.

It is a $122M project with 65 percent of funding provided by the Army Corps.

The Arizona Department of Transportation recently closed Historic Route 66 to make way for the start of construction.

Crews are installing precast bridge girders and pouring a new bridge deck. Fabricating the bridge components ahead of time as opposed to building them in place allows the work to be executed more quickly, reducing the time needed to replace the bridge and impacts to traffic.

ADOT Resident Engineer Nate Reisner said using those precast bridge components greatly reduces the time needed for closures.

"Basically, with this project, we built a big Lego set," Reisner said in an interview with the Arizona Daily Sun. "We're going to come in here and we're going to set those concrete blocks and make a new bridge."

Before construction started, crews spent time relocating pre-existing utilities in the area such as sewage pipes and cable lines.

"So that's what people have seen, the sideways drilling that looked like it was foundation work maybe for the bridge, but it wasn't," Reisner said in the interview. "It was utility relocation that had nothing to do with it."

Construction along the Rio de Flag and Clay Avenue Wash will increase the capacity of the channel and significantly reduce flooding in neighborhoods such as Southside.

Project scope and benefits include:

• Increasing the capacity of the Rio de Flag channel to contain the 100-year storm event;
• Construction of underground and surface flood way structures;
• Construction of a composite channel (both above and below ground) in the Upper Reach north of City Hall to provide stormwater surface flow;
• Realignment of the primary floodway to the south of the BNSF Railway corridor to reduce the amount of stormwater in the Southside neighborhood;
• Utility relocations, landscaping and re-vegetation, and street reconstruction;
• Neighborhood stormwater connections will be reconstructed with the project, or planned as future improvements as needed.

Project Potential

Once completed, this project has the potential to prevent damage to approximately 1,500 structures in Flagstaff, valued at more than $916 million. The project also will remove the probability of $93 million in economic damages due to flooding and remove restrictive requirements for floodplain redevelopment.

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