Caution: Bridge work ahead

LOWELL -- The rivers in Lowell have defined this city. They've powered its mills, framed its vistas, and floated its barges.

Unfortunately for Stephen Curran, the city engineer, people keep wanting to cross them.

For Curran, the man in charge of maintaining the spider web of bridges that crisscross this city's rivers and canals, that is one big headache. Because besides being grand and romantic and useful, the bridges in Lowell -- and across much of the state -- are, as a rule, old and poorly maintained.

There is the Rourke Bridge, erected as a temporary span -- 21 years ago -- with its rotting pilings. The Market Street Bridge that crosses over the Western Canal with its rickety skin of steel plates to cover crumbling asphalt. And the Textile Memorial Bridge with its rotting floor beams and disintegrating deck.

''We're not in great shape," Curran said ruefully. ''There's a huge backlog of projects, and it's getting bigger and bigger all the time."

Curran estimates the cost of repairing the bridges in the city at well over $15 million. He has $250,000 in the bank. He estimates he needs about $2.5 million to keep up with regular bridge maintenance. His annual budget? About $40,000.

Across Massachusetts city engineers like Curran are sweating through fitful nights as the Commonwealth's 5,000 bridges deteriorate faster than they can be repaired or maintained.

Approximately 560 of the 4,400 bridges that MassHighway inspects and maintains are listed on a federal database as ''structurally deficient." The designation does not mean that the bridges are dangerous. Rather it means the spans have problems that need to be corrected.

Closer to home, 38 of the 498 bridges in communities northwest of Boston are considered structurally deficient. Another 183 have been deemed functionally obsolete -- meaning they can no longer handle the quantity of traffic with which they are faced.

And that's not even the bad news. As bridges built between 1950 and 1970 -- called baby-boomer bridges -- reach the end of their useful life span, hundreds are on the verge of needing replacement over the next 10 years, according to a November 2005 report produced by the Massachusetts Infrastructure Investment Coalition.

In all, 1,857 Massachusetts bridges were built in the 1950s and 1960s. That 20-year period was the largest bridge construction boom since the 1930s, when 612 spans were built in the state.

But the damaging northeastern combination of freezing and thawing, salting and plowing, and increasingly heavy traffic puts the life expectancy of most bridges around 50 years -- a number that can be marginally extended or diminished depending on how a bridge is maintained. To extend that life span, the Massachusetts Infrastructure Investment Coalition urges a massive increase in maintenance so the state will avoid having to build new bridges just as the baby boom generation reaches retirement and taxes the state's social safety net.

The difference between investing $100 million a year and investing $200 million a year over the next five years will mean the difference between 647 bridges needing to be replaced by 2010 as opposed to 443.

''We're at a critical point," said Abbie Goodman, executive director of the American Council of Engineering Companies of Massachusetts at the Engineering Center in Boston. ''We need to spend some money annually over the next six years on maintenance, or there's going to be hundreds of structurally deficient bridges."

Between 2002 and 2005, the state spent an average of $174 million a year on bridge repair. But cuts to this year's federal transportation bill meant that Massachusetts received 17 percent less than it expected, according to Jon Carlisle, a spokesman for the State Department of Transportation.

The $200 million a year figure may sound high but, as a rule, bridge construction and repairs are drawn out and expensive, involving several agencies and a labyrinthine permitting process.

Add to those conditions a community's concerns about historic preservation and aesthetic sensitivities, and replacing a bridge can easily eat up a decade from start to finish.

In Lowell, the Textile Memorial Bridge was built in the 1890s, closed in 2003, and given a repair that was supposed to last five to seven years. A $25 million replacement bridge is expected in 2009.

''God help us until then," said Curran. ''These bridges don't last forever."

In Concord, chunks of concrete have been falling off Heath's Bridge into the Sudbury River for five years, said Jim Shuris, Concord's town engineer. The latest hole opened up last month, so the town did what it always does: It laid a 20-foot steel plate over the hole and shut down a lane. But at this point, repairs are like darning a sweater that is unraveling faster than it can be stitched together.

''It's in horrible shape," Shuris said.

The hole was the fourth one in three years, Shuris said. ''The concrete literally crumbles in your hand." Each time a hole needs patching one lane of the bridge needs to be shut down, and the cost of the repair is about $20,000.

''At this point it's throwing good money after bad," Shuris said. The bridge, which was built in 1967 and is crossed by about 8,300 cars a day, has been in need of a major rehabilitation for at least five years.

The holdup? Permitting. Among the concerns: The Natural Resources Commission in Concord wanted a critter crossing under the bridge so animals wouldn't get run over on the road. The state vetoed the idea, but the veto had to be justified and explained.

''Building a bridge isn't as easy as having your engineers design it with blindfolds on," Shuris said. ''Everybody has a say and it takes time."

Across town Flint's Bridge on Monument Street, which crosses the Concord River, adds character and charm to the town, but the stone arches have been crumbling for years. The final straw that got it some attention was the inadequacy of a thin steel rail that separated cars from the edge of the bridge. In November of 2004 that rail didn't stop a 17-year-old girl driving her family's SUV from smashing through it and landing in the water below.

The driver, who was reaching down to pick up a CD off the floor, according to police, allowed the SUV to drift just a few feet to the right -- enough to send the car plummeting into the water 10 feet below. She and her passenger walked away unharmed. The SUV was totaled.

Since then Jersey barriers have been installed to prevent another vehicle from going over the side of the bridge, but it will be at least another year before the bridge is repaired, Shuris said.

Sometimes it takes a natural catastrophe to speed things along.

In Methuen the Lowell Street Bridge, which had been getting worse for years, finally washed away during a tremendous flood on Easter Sunday, 1999. At the time the bridge was open and it was just sheer luck that no one was crossing when it fell.

''My reaction was, thank God nobody got hurt," said Ray DiFiore, public works director for the city. The bridge had been on the state's list for several years before it was destroyed. After it was demolished, however, things moved quickly. Another bridge was up in less than a year.

''It was like a miracle," DiFiore said. ''Of course it practically took an act of God to demolish it first, but when the state wants to act, they can."

Douglas Belkin can be reached at dbelkin@globe.com.