Thousands of commuters heading for downtown Salt Lake City each day exit I-15 at Sixth North and travel east across a viaduct spanning wide railroad yards. Motorists probably don't realize the bridge is falling to pieces.

"It's one of the worst bridges we have locally," said Ron Rasmussen, a bridge inspector for the Utah Department of Transportation. "We keep a close eye on it."A walk beneath the viaduct reveals long cracks in support columns. Concrete chunks have fallen from overhead sections, exposing bare reinforcement steel.

Rasmussen said that is caused by the salt put on streets to melt snow. Salt solution seeps to the steel, corrodes it and makes it expand - which cracks away the concrete encasing it. Reports estimate that at least $3 million is needed to repair the damage.

The deteriorating Sixth North viaduct is just one of 332 bridges in the state that are classified "deficient," according to state and federal inspection reports examined by the Deseret News.

The state and local governments have oversight for 2,463 bridges - so that means one of every 13 bridges in Utah is deficient. While that is worrisome, it is not as bad as the national average, which shows 42 percent of all bridges to be deficient.

That doesn't mean all the deficient bridges are structurally unsafe, although many are. The "deficient" classification may mean a bridge is too narrow, isn't designed to carry its present loads or is badly deteriorating and needs prompt repairs - even if it is not expected to fail in the near future.

Utah records estimate that the cost to replace or renovate the 332 deficient bridges is $103.7 million. Officials say because of that high cost, Utah won't be able to repair all the deficient bridges for decades, although the worst should be fixed in five to eight years. Still, motorists will continue crossing many troubled bridges unaware of the problems lurking below.

Reports predict that many of Utah's other bridges are also expected to soon deteriorate to the point that they will also be considered deficient.

To top it off, records show that even minor maintenance recommended by inspections to keep bridges in good repair is often left undone, also apparently because of tight budgets.

Such problems concern both state and federal officials, who do what they can within existing budgets to overcome them.

Reasons for concern are easy to see. Several bridges nationally have collapsed in recent years killing dozens - and investigations showed the collapses could have been prevented with better maintenance and inspection.

For example on April 5, 1987, a New York State Thruway bridge over Schoharie Creek collapsed and killed 10 people. In 1983, a Connecticut Turnpike bridge fell into the Mianus River, killing three. Forty-eight people died in the 1967 collapse of the Silver Bridge into the Ohio River - a disaster that led to creation of a "national bridge inspection standard."

Following is an overview of the current condition of Utah bridges, their lingering problems, funding difficulties and predictions about the future:

CONDITION OF UTAH BRIDGES - Of the 332 bridges that are considered deficient, 82 are on state and federal highways maintained by UDOT and 250 are on local roads maintained by cities and counties.

UDOT inspects all the bridges and gives each a "sufficiency rating" from 0 to 100, based on its structural safety, whether design features are obsolete and how essential its use is to the public.

A rating lower than 80 puts a bridge on the "deficient" list and means the bridge should be renovated. Federal guidelines say a rating lower than 50 means the bridge should be replaced.

Records show that 102 of the deficient bridges have ratings between 50 and 80 and are in the "should-be-repaired" range. And 230 have ratings lower than 50, putting them in the "should-be-replaced" range.

Some Utah bridges have extremely low ratings. Twelve have ratings lower than 10, with four receiving a mere "2" - but two of these have been closed.

Records show that an additional 34 bridges have ratings between 10 and 19, 47 have ratings between 20 and 29 and 61 have ratings between 30 and 39.

A low sufficiency rating does not always mean that a bridge is expected to fail - just that it is in need of repair or upgrading. Inspectors assign another set of numbers from 0 to 10 to rate the structural condition of bridges.

The Deseret News obtained those ratings for 289 of the deficient bridges in the state. The ratings show that more than two-thirds of them have serious structural problems.

For example, 150 received a structural safety rating of "4," meaning they are in "marginal" condition and the potential exists for major rehabilitation - and "immediate rehabilitation (is) necessary to keep (them) open," federal guidelines say.

Twenty-two received a "3," meaning they are in poor condition, need immediate repair or rehabilitation and should be closed to heavy loads.

Records show that 29 received a "2," meaning they are in "critical condition - the need for repair or rehabilitation is urgent" and it "warrants closing bridge to all traffic," according to federal guidelines. However, records show many bridges with a "2" rating still have not been closed.

Also, five bridges were rated "0" structurally, meaning they are in "critical condition - facility is closed and beyond repair." But they are still listed on state and federal bridge inventories in hopes that money will become available to replace them.

LINGERING PROBLEMS - Many of the problems that have caused the low ratings for bridges have been noted in inspections over and over for years.

An example is the large bridge on US-89 over the Ogden River at 20th Street and Washington Boulevard in Ogden.

An archway sign over it says, "It pays to live in Ogden." But problems below - ranging from abutment erosion to extensive concrete deterioration - have made inspectors recommend for the past 12 years that the bridge be replaced. It is still used on the major highway.

A report form shows an inspector wrote on May 28, 1976, under space for recommendations about the bridge, "REPLACE." An inspection three years later reiterated, "Replace bridge." The same advice was given in 1982 and 1984.

Then an inspector last year wrote, "Need to replace structure is getting critical."

Another example of problems worsening through inaction and time is a bridge on U-126 over railroad tracks two miles north of an intersection with U-26 in Weber County.

An inspection in 1979 noted that bearings on the bridge had completely failed. In 1982, an inspector wrote repair of the bearings was still needed, but the "No. 1 priority should be getting (the) bridge completely replaced."

In 1987, an inspector wrote, "Condition of bridge is such that if the bridge cannot be replaced in six months, it should be posted for 24,000 pounds tandem axle load limit."

The structure's "sufficiency rating" dropped from a 21.1 in 1984 to a mere 2.0 in 1987. Records indicated it is still being used.

FUNDING PROBLEMS WORSEN BRIDGE PROBLEMS - David Christensen, chief structural engineer for UDOT, said officials are limited by tight budgets on how much repair and maintenance work they may do - even though they receive assistance through the federal bridge replacement program.

For example, he said UDOT is usually able to do about $6 million to $7 million worth of bridge maintenance work a year and about $3 million worth of bridge replacement.

That may not stretch far, considering that the $3 million needed to repair just the Sixth North viaduct would take all the repair money normally used in a year.

Still, Christensen said, the state should be able to adequately repair the more major bridge problems on state and federal roads in five to eight years.

To stretch available money, Christensen said the state has implemented a policy requiring officials from UDOT headquarters to meet each year with regional UDOT officials to discuss which structures qualify for the federal bridge replacement program.

"Anything that is structurally deficient we post against heavy loads or get a contract out to replace or repair," he said. Officials also decide which bridge work is less important and should be delayed because it is on less traveled routes or because problems are relatively minor.

For bridges on county and city roads, Christensen said UDOT sends local governments copies of inspection reports and recommendations for repair and replacement. But local governments decide when or whether to take action - and they maintain the lion's share of deficient bridges in the state.

Christensen said the state diverts 35 percent of the money it receives from the federal bridge replacement program to local governments - the maximum it may give them legally.

That money may be used to pay for 80 percent of construction costs - but the local governments must pay for all the engineering and 20 percent of the construction - an amount most of them find difficult to produce.

MORE DETERIORATION COMING - Even if the state - as Christensen predicts - can repair the worst bridge problems on state highways in five to eight years, federal and state officials are expecting many other serious problems to emerge and replace them on project priority lists.

As a report from the U.S. Secretary of Transportation to Congress last year said, "Bridge decks built without corrosion protection for reinforcing steel (which describes many Utah bridges) can be expected to last perhaps 30 to 40 years before replacement or major rehabilitation is required.

"In severe environments, where traffic or winter salt applications are heavy, bridge decks often experience shorter life."

Christensen said Utah found out the hard way that statement is true, especially along its interstate freeway system. He said bridges without corrosion protection were found to have serious problems after only 10 to 15 years, and were deteriorating six to 10 times faster than normal.

The problem comes because the chloride in salt sets up an electrical galvanization reaction with the steel in bridges that is similar to the reaction in a storage battery. It corrodes the steel, which makes it take more space and crack off the surface of the concrete it is designed to reinforce.

Christensen said when the state realized what was happening in the mid-1970s, it coated bridge decks with a rubberized membrane with asphalt on top to help keep salt solution from seeping to the steel. He said that worked well in many areas of the country, but did not have great success here.

After 10 to 12 years with that protection, a lot of cracking from salt was still noticed.

The state tried to help some of those bridges with "cathodic protection," a system to reverse the electrical reaction that corrodes steel. But it determined that would generally cost too much for the benefits received.

Christensen said the state now puts a protective layer of latex-modified concrete on troubled bridge decks to stop salt seepage, which he says should add another 10 to 15 years of life to the decks.

But he said no protection system seems to be foolproof. For example, most older bridges have deck joints that are almost impossible to seal, he said.

"As we take some projects off the top of the list, additional ones always come on the bottom," he said.

Much of the deck renovation on freeway bridges in Salt Lake County is on hold pending a study on how to improve transportation in the central I-15 corridor. Because some proposals call for adding lanes to the freeway, Christensen said many of the troublesome decks may be removed and expanded anyway.

Also, UDOT will not allow any bridges to remain open if it fears any sort of imminent collapse. Christensen said UDOT has a machine that will exert four times the pressure of a legal load on a bridge deck. "If it can handle that load, we figure it's pretty safe."

MORE PROBLEMS, BUT NO MORE FUNDS - While officials foresee continuing and possibly increasing problems with bridges, they predict that government funds will likely not increase to help solve them - which could set state and local governments even further back in the race to keep ahead of deterioration.

Rep. Boyd L. Warnick, R-Salt Lake, chairman of the House Transportation and Public Safety Committee, said, "Because of tight budgets, I would predict that funding would stay pretty much the same" from both state and federal levels in the foreseeable future.

But he also said he doesn't feel that will be sufficient, and the state may need to look at some heretofore unpopular means of raising money for bridges and highways.

"Toll roads are a possibility. They are unpopular, but are a possibility. Raising gasoline taxes is also a possibility, but is not a welcome topic to anyone. And perhaps there is some potential in using public/private sector mechanisms used in other states.

"That is where some private entities that benefit from improved highways help provide funding for them," he said.

"When we look at our long-range needs five years and more down the line, it's clear that we will be deficient in meeting even minimum needs," Warnick lamented. "It's a tough situation, like they always are when dealing with public policy."

Utah's 10 worst bridges still in use

Sufficiency ratings range from 0 to 100. The lower the score, the more deficient the bridge.

SOURCE: Utah Department of Transportation

Location Sufficiency Rating

Carbon County road over Pricer River,

1 mile northwest of Price 2.0

U-126 over railroad, 2.5 miles north of U-26 2.0

Duchesne County road over Neola No. 1 canal,

4.5 miles northeast of Neola 3.0

Hill Street over Price River, west of Main St. in Helper 8.4

CarbonCounty road over Quinn Wash

3.5 miles northwest of Wellington 8.4

Millard County road over DMAD Reservoir Canal

1 mile northeast of Delta 9.1

Cache County road over Little Bear River,

2.5 mile south of Paradise 9.6

Uintah County road Ashley Creek,

1.5 mile north of Maeser 9.8

Bridge over Provo River at 850 W. Ninth North in Provo

10.6

Duchesne County road over Duchesne River,

1 mile northwest of Tabiona 11.1