Study says I-10 bypass in Arizona ‘feasible’ but costly

By PAUL DAVENPORT
The Associated Press

3/19/2008

PHOENIX — A new study commissioned by the state says a proposed bypass for Interstate 10 that would divert long-distance traffic around the Phoenix and Tucson metro areas appears to be necessary and is technically feasible.

But the study for the Arizona Department of Transportation acknowledges there’s extensive opposition to some possible routes. Also, the 250-mile project would be costly and doesn’t have a funding source, according to the study.

The study conducted by San Francisco-based URS Corp. and another firm is being submitted to the state Transportation Board for discussion and possible action at a meeting Friday in Tucson.

The department released the report in advance of the meeting in response to a public records request by The Associated Press.

I-10 is both an east-west route for long-distance truckers and other cross-country travelers and a major connector between the state’s two largest metro areas. It also bisects Pinal County, a fast-developing area sandwiched between Phoenix and Tucson.

I-10 is already being widened to four lanes in each direction through Tucson but there isn’t room to add even more lanes and the new capacity won’t be enough to handle future local and long-distance needs, including truck traffic, the study stated.

“Given the expected worsening traffic congestion in Tucson and the absence of a suitable alternative route, there appears to be a need to further consider bypass alternatives for I-10 in southern Arizona,” the study stated.

Possible bypass routes include highway corridors that would split off from I-10 to the east of Tucson before reconnecting with either I-10 or I-8 in Pinal County. A possible Phoenix bypass could connect the Tucson bypass with I-10 west of Phoenix.

With expected urban growth in Pinal County, “I-10 will essentially become an urban freeway” in much of the bypass area, the study said. “This means that interstate traffic on I-10 (including many trucks) will be subjected to the typical urban peak-hour congestion for 150 miles in Arizona.”

Some of the routes would cross largely undeveloped valleys of southeastern Arizona desert hill country east of Tucson, though the study said all but one route would avoid environmentally protected land. The exception: a two-mile stretch west of Tucson that’s a wildlife mitigation corridor for an unrelated project.

However, residents and conservationists object to either the entire bypass proposal or at least some routes as unnecessary, costly and damaging.

Of particular concern, the study acknowledged, is the unspoiled San Pedro River Valley and its riparian habitat between Benson and Mammoth.

Construction in some areas would require major new bridges in rugged terrain and crossing numerous washes but would not be an extraordinary challenge, the report said. “If properly designed, the road would provide a very scenic drive for motorists.”

Segments of I-8 and State Route 85 south and west Phoenix already are being upgraded as a four-lane, limited-access route for I-10 traffic to bypass Phoenix.

That “probably will have the capacity to accommodate the bypass traffic demand for many years” but not further down the road as additional freeways are needed to handle additional growth further to the west in Maricopa County, the study said.

Building the entire 250-mile bypass route would cost between $6 billion and $8 billion, the study said.

It would take 10 cent increases of both federal and state fuel taxes to pay for the project because their revenue is being outstripped by rising construction costs, the study said. “The bypass cannot be constructed with current funding levels.”

Using tolls is an option but traffic volumes may not be enough to make it work, at least for the entire cost, the study said.