One of the Northwest's busiest, most congested intersections may get a lift as part of the next Interstate 10 construction project.
Ina Road crosses the Union Pacific Railroad and I-10 as motorists access the highway, or move between densely developed southern Marana, unincorporated Pima County and into the city of Tucson.
As part of the Interstate 10: Ina to Ruthrauff project now under analysis by the Arizona Department of Transportation, study of the Ina traffic interchange may result in its elevation, with construction of a roadway high above the Union Pacific Railroad tracks and the highway.
It's a complicated engineering scenario, explained Joe Chang, a professional roadway engineer with URS Corp., one of the project's contractors.
A traffic analysis planned in early 2010 would identify "as many lanes as needed" on all roadways through the corridor into the year 2040. Ina now comes across I-10 with two lanes in both directions, and at the same grade as the Union Pacific Railroad, which is constructing a second set of tracks.
How many lanes might Ina become? "We don't know," Chang said at an open house on the project last week. "Traffic volumes will tell us. Definitely more than three."
It'll be far above the other surfaces. The railroad requires a 23-1/2-foot vertical clearance over the top of its tracks. With the super structure of the bridge descending up to seven feet, that means the Ina road surface might be 30 feet over the railroad tracks. If that's the case, frontage roads parallel to I-10 would have to be brought up, and the interstate itself must be lowered.
"It's not just improving the traffic interchange, it's rebuilding the interstate," Chang said. "Our biggest challenge in the Ina geometry is to do our best to accommodate the businesses" along Ina.
Work to improve the Ina Road traffic interchange would have access to an estimated $54 million. Funds would come from the Regional Transportation Authority and its voter-approved sales tax, as well as other regional sources, according to ADOT information.
Along with Ina, the I-10: Ina to Ruthrauff project includes likely elevated crossings at Sunset and Ruthrauff, widening of I-10, and the evaluation of structures over the Canada Del Oro Wash and the Rillito River. Those bridges must be elevated to accommodate the 100-year storm event and its volume of water. The model for analysis of I-10 does include the Twin Peaks interchange, now under construction between Cortaro and Avra Valley roads across I-10.
For the entire six-mile I-10 project, a draft traffic report would be generated in January. Alternatives would be identified in April. Draft environmental reports are projected for September. Draft environmental analysis would be due in November. A draft implementation plan would come out in March 2011, followed by a final environmental analysis in May 2011, then a final design.
"We're envisioning needing federal funds to build something of this magnitude, so we're following federal guidelines" with regard to environmental study, said Mike Bertram, senior project manager with HDR Engineering.
Comments are needed by Dec. 2. They may be submitted by letter, comment form or e-mail to ADOT in care of Paki Rico, 2540 N. Tucson Blvd., Tucson, 85716; by e-mail at firstname.lastname@example.org, or through the website, i10tucsondistrict.com/itor.html.