As bad as Tucson's streets are, they're jewels compared with the dozens of crumbling bridges that dot the community, according to data from the Federal Highway Administration.

Just fixing the problems with state bridges will cost $1.4 billion over the next 25 years. No estimates are available for those maintained by cities and counties in the region that are listed as either structurally deficient or functionally obsolete.

All the bridges in Pima County are considered safe, but many require significant maintenance or rehabilitation, and in a handful of cases, replacement.

They are not being ignored, per se. But municipal budgets can no longer afford the millions of dollars to bring them all up to modern standards without federal assistance.

Local governments have become reliant on a heavily competitive funding mechanism that pits a bridge in Tucson against a highway in Tallahassee and a flood-control project in Tacoma.

Securing funding for the 22nd Street bridge over Aviation Parkway and the Union Pacific rail lines, one of Tucson's most widely recognized problem bridges, took nearly a decade, said Daryl Cole, the city of Tucson's director of transportation.

With a federal rating of 69 (out of 100,) it is far from the city's worst. But it gets a lot of notice because the 48-year-old structure carries nearly 50,000 vehicles a day, delivering commuters to their jobs, classes and homes.

Because it is in a highly urbanized area, construction of a new bridge will require buying numerous homes and businesses for right of way and to span the entire rail yard and eight lanes of parkway. Cole says it will cost up to $50 million to replace the bridge. Work is expected to begin in about three years.

4 percent rated deficient

In all, 43 of the roughly 1,200 bridges and other bridgelike structures in Pima County are listed as structurally deficient.

This rating is based on biennial inspections of the deck, superstructure and substructure of each one. On a 0 to 9 scale, the minimum acceptable rating for any of those elements is 4 for the bridge "to be left in place as is."

Another 70 bridges are listed as functionally obsolete, built to a standard no longer adequate for their current use.

With almost no money for bridge maintenance beyond inspections, officials have become increasingly reliant on decreasing the weight limits for large trucks using bridges rather than making expensive fixes.

The practice, known as load-limiting, extends the life of the bridge by decreasing the strain cause by extremely heavy loads.

The federally-mandated sufficiency rating - different from the 0-9 rating used to label bridges as structurally deficient or functionally obsolete - has some bridges getting single-digit ratings when graded on a scale of 1 to 100, according to data from the Federal Highway Administration.

Others are so narrow (a few built in the 1930s are still a single lane wide) they become bottlenecks during rush hour.

The rating uses a complicated formula based on information from 20 different fields - everything from its structural evaluation to whether the public still uses the bridge goes into the calculation.

A low rating can be generated for a number of reasons including a low vertical clearance and narrow lanes. These ratings are not, officials agree, a yardstick on whether a bridge is in imminent danger of collapse.

Load limits

The 22nd Street bridge over Aviation Parkway is by no means the only example of a bridge that has been increasingly reliant on weight restrictions to delay the multimillion-dollar cost of replacement.

Both Tucson and Pima County regularly receive requests to approve routes for oversized or overweight trucks, seeking either a one-time crossing of a problem bridge or choosing another route.

The county, for example, has been rerouting heavy traffic along Houghton Road near Interstate 10 to Rita Road for years, rather than having heavy trucks cross over the structurally deficient and functionally obsolete bridge over the Union Pacific rail lines.

County officials are expected to put new weight limits on the Houghton Road bridge later this year. Eventually, it's projected to cost $5 million to replace it with two three-lane bridges.

Bridges are safe

The collapse of the Skagit River Bridge along Interstate 5 in between Seattle and Vancouver, British Columbia, last May drew the national attention back to bridge safety.

The bridge itself was rated in relatively good condition, but collapsed after a semi-truck hit multiple sway braces on the right side of the truss structure.

Rick Ellis, the engineering division manager for the Pima County Department of Transportation, says the collapse proves all bridges are far from invulnerable.

"Any bridge can be susceptible to damage from a catastrophic accident," Ellis says.

Although many of our bridges were rated inadequate in some way, no bridges in Pima County are actually dangerous, said Priscilla Cornelio, director of the county Transportation Department.

Following the failure of several bridges in Tucson during a massive flood in 1983, Pima County developed plans to monitor structures during severe storms. The county regularly evaluates the bases of structures, and closes them if there is any concern the aggregate material under the concrete structures is in danger of washing away.

County bridge engineer David Zaleski says he has no concerns about driving over bridges that have had weight limits lowered, noting he uses the 22nd Street bridge on a regular basis.

Az bridges relatively young

Overall, Arizona ranks fairly high, as far as states with the fewest bridges needing maintenance, but not because the state is necessarily doing a better job taking care of them.

The state's infrastructure is relatively young when compared to the rest of the nation's, and most counties in Arizona lack an annual freeze/thaw cycle, which reduces the life of a bridge.

The average age of bridges in Pima County is 38 years, compared with a national average of 43 years.

The life span of a new bridge is 75 to 100 years.

Harsh winters can wreak havoc on the bridge's deck and support structure, weakening them over time. The continued application of road salt to melt ice can lead to the erosion of the top layer of pavement.

Still, Transportation for America, a national group, notes that Arizona is one of 15 states where the number of functionally obsolete bridges has grown in the last decade.

Staggering cost

A report from the Arizona Department of Transportation suggests the state will need $1.4 billion over the next 25 years to replace 604 bridges and widen another 195.

ADOT spokesman Dustin Krugel noted that the department's recently-approved five-year plans call for $200 million in bridge maintenance over the next five years.

But with $1.4 billion in identified needs, Steve Boschen, deputy state engineer for design, says funding will be a challenge for all state transportation departments in the coming years.

"It will be important for us to identify additional funding mechanisms to maintain our existing bridge assets, as well as modernizing where growth demands," he said.

Adding to the problem is a new federal funding system that has made it more difficult to secure such funding.

The old pot of dedicated federal funding set aside for bridge maintenance has been replaced with a system requiring different types of construction projects, other than bridges, to compete for funding.

"You are fighting with all other projects," said Cole, of the Tucson Transportation Department. "Thankfully, we don't have huge issues" with bridges needing to be replaced.

On StarNet: How safe are the bridges you cross regularly? Check a list at azstarnet.com/multimedia

Contact reporter Joe Ferguson at jferguson@azstarnet.com or 573-4346.

Structurally deficient bridges in Pima County

In 2013, 43 of the roughly 1,200 bridges and other bridgelike structures in Pima County were listed as structurally deficient. 

This rating is based on biennial inspections of the deck, superstructure and substructure of each one. Bridges rated 100 are perfect.

Structure Feature Average Daily Rating Year built
HOUGHTON ROAD P RAILROAD 200 11.4 1935
IRR BIA RTE 10 WASH 0 17 1950
TRICO RD SANTA CRUZ RIVER 1850 18.8 1962
MILE WIDE ROAD JONES WASH 50 21.6 1965
RIVER ROAD VENTANA WASH 4000 24.2 1967
MILE WIDE ROAD BRAWLEY WASH 50 26.3 1962
HOUGHTON ROAD SMALL WASH 3500 27.8 1962
TRICO-MARANA ROAD SANTA CRUZ RIVER 1000 31.6 1959
TELERA ST (AJO) AJO WASH 200 33 1935
IRR BIA RTE 161 WASH 250 33.4 1998
IRR MISSION RD MINE HAUL ROAD 400 38.1 1973
I 10; WB EARP WASH TRIB 27000 51.9 1958
INA ROAD SANTA CRUZ RIVER 13900 52.2 1977
WB FRONTAGE ROAD EARP WASH TRIB 1200 56.3 1960
I 10; WB CIENEGA CREEK 27000 59.5 1961
I 10; EB RUTHRAUFF RD 70500 61.8 1965
I 10; EB INA ROAD 42250 63.9 1965
I 10; WB INA ROAD 42250 63.9 1965
I 10; EB CIENEGA CREEK 13500 64 1955
I 10; EB AJO WAY 37600 64.2 1965
I 10; WB AJO WAY; FAU 8173 37600 64.2 1965
I 10; EB CRAYCROFT RD 27000 66 1960
I 10; EB WILMOT RD 24500 66 1960
I 10; EB COUNTRY CLUB ROAD 33450 66.6 1966
I 10; WB PALO VERDE ROAD 31076 66.8 1967
CALLE SANTA CRUZ VALENCIA WASH 1000 67.8 1984
22ND STREET SPRR; AVIATION HWY 49686 68.6 1965
I 19; W FR RD OLD JUNCTION WASH 50 68.9 1932
I 10; FRONTAGE RD WASH 400 69.9 1929
AVRA VALLEY ROAD E BRANCH BRAWLEY WASH 2000 79.2 1957
I 10; WB CRAYCROFT RD 27000 82 1960
I 10; WB WILMOT RD 24500 82 1960
IRR I 19; SB PIMA MINE RD 17500 92 1968
IRR I 19; NB SANTA CRUZ RIVER 20050 94 1967
IRR I 19; SB SANTA CRUZ RIVER 20050 94 1967