When the City Council approved plans for the downtown Rio Nuevo project in April, it also OK'd a long-term design concept for radically altering I-10 from 22nd Street to Congress. The proposal calls for eventually depressing the interstate to eliminate the existing berm-like barrier that physically divides the project. This depressed roadway would allow both a visual and transportation link between Rio Nuevo's two major areas, located on either side of the highway.
John Jones of the city's Rio Nuevo office says a rough cost figure for the work, including building necessary bridges over the man-made canyon, would be $80 million. If a deck were placed on top of the depression, similar to one that has long existed in central Phoenix, Jones estimates the cost of the project would double.
Officials with the Arizona Department of Transportation don't express a lot of enthusiasm for the proposal. Bill Higgins of ADOT's Phoenix office says, "We only have X amount of dollars for I-10 improvements and we'll throw that money into the pot. But the city would have to pay the rest."
Larry Maucher, a local ADOT engineer, questions how flooding from the nearby Santa Cruz River could be prevented from submerging a depressed I-10. The river, he points out, is only an eighth of a mile away from the interstate, and it sometimes does flood.
The city is going to have a consultant look at that issue, according to Jones. They'll also review ways to drain the depression and see if the groundwater table beneath the river would impact it.
Depressing the roadway, Jones says, is a long-term proposal intended to be implemented 10 years or more from now. In the next decade, the Rio Nuevo plan calls for developing three "penetrations" underneath the interstate.
One of these would use the existing underpass at Clark Street south of the Tucson Convention Center. Improvement of this subway would continue the current vehicular access while also allowing a trolley line to run to the Rio Nuevo development on the west side of I-10. To the east, this new rail line would wind its way through downtown, eventually ending up at the train depot near Fourth Avenue and then going on to the University of Arizona.
The Rio Nuevo plan also calls for creating a pedestrian underpass beneath I-10 just north of Clark Street. A new vehicular tunnel would be developed as an extension of the existing Mission Lane along the southern boundary of the project.
But these proposals exist only on paper. For its part, ADOT is proceeding with implementing a $250,000 gateway feature at the Congress Street on/off ramp, and planning to spend $85 million in the next five years to widen I-10 between Congress and Prince Road to eight lanes of traffic. At the same time, the state agency will be reconstructing the nearby I-10/I-19 interchange, at a total projected cost of $60 million.