A bridge collapse figured prominently in Minnesota legislators' minds in 2008, the one and only time they boosted transportation funding in the past 27 years. Can warnings about troubled bridges pry a transportation bill out of conference committee this year?

A gaggle of county commissioners hopes so. Five leaders of the Association of Minnesota Counties appeared at the State Office Building on Thursday to instill a little fear about deficient bridges in compromise-averse legislative hearts.

They were armed with a timely report from the nonpartisan advocacy group Transportation for America that ranks Minnesota counties by the condition of their bridges. In 13 of the state's 87 counties, at least 10 percent of bridges have been rated "structurally deficient" — that is, still usable but past their intended life span, exhibiting deterioration and likely to need either replacement or closure within a few years.

Of note for the rural-focused House Republican majority: 12 of those 13 counties are in Greater Minnesota. Carver is the only metro county on the worst-bridges list. (I felt sorry for bad-bridge leaders Lincoln, Pipestone, Redwood and Mower. Only the day before, they'd been told at another Capitol news conference that their region suffers from the state's poorest water quality. Add drought and bird flu, and this spring's worry list in southern and southwestern Minnesota is getting pretty long.)

Metro folk also have bridge concerns. Take state Sen. Kari Dziedzic, DFL-Minneapolis. A recent visit to her office turned into a seminar on the status of the 11 auto and 40 or so railroad bridges in her northeast Minneapolis district, which is bounded on the west by the Mississippi River. Dziedzic grew up two blocks from the river's East Bank.

One of the 11 is the bridge whose mention still tugs at heartstrings — Interstate 35W, where 13 people plunged to their deaths and 145 were injured on Aug. 1, 2007. That collapse, federal investigators found, was primarily caused by an original design error made 40 years earlier.

Understandably, "we're very sensitive to bridges in my district," Dziedzic said. With a poster-sized map of District 60 and a laser pointer in hand, she led a bridge-by-bridge verbal tour from Camden (rehabbed in 2011-12) and Lowry (replaced in 2012) in the north to Franklin (due to be closed for repair next year) on the south side of her district.

Each bridge has its own story. But one theme emerged in Dziedzic's telling: Bridges either first built or last renewed in the 1970s need fixing now. Their condition is worsening rapidly. Wait a few years, and such bridges will require replacement, not repair. When that happens, costs double or triple.

That jibes with what Jim Erkel of the Minnesota Center for Environmental Advocacy calls the "pig in the python" problem with Minnesota transportation needs.

A lot of road- and bridge-building happened in the 1960s and 1970s, and that infrastructure is rapidly aging now. It's a phenomenon baby boomers should understand well.

The Federal Highway Administration says that nearly a third of Minnesota's 13,000 bridges will pass their 40th birthday in the next decade. That will make them as old as the original I-35W bridge was when it fell.

One bridge has Dziedzic's focus. "The 10th Avenue bridge is at a tipping point," she said. It's a bridge that was sealed in local memory eight years ago as the nearest neighbor of the fallen I-35W span. It's the emergency-­vehicle gateway to the University of Minnesota's East Bank campus should the new freeway bridge ever be unavailable.

It fits the pattern: Built in 1923, it underwent its last major overhaul in the 1970s. Between 2008 and 2013, "field observations revealed a substantial increase in the deterioration of components," a city-issued description says. "Leaking joints in the deck have led to deterioration of the deck / floor beams / spandrel columns / arch ribs / and piers." That's pretty much the entire structure, a diagram shows.

The 10th Avenue bridge tops this year's city of Minneapolis requests at the Legislature. The plea is for 75 percent of the costs of a $42.5 million project, or about $32 million. The city proposes to cover the rest.

That funding could come in either a transportation or a bonding bill. But the bonding committees have barely stirred all session. And transportation is caught in a partisan staredown, with DFLers insisting on a gas tax increase and Republicans just as adamant that no tax be raised this year, for transportation or any other purpose. That's an impasse that could make this a "no bill" year for both transportation and GOP-backed tax cuts. DFLers won't let Republicans have their way on both.

Pass no transportation bill this year, Dziedzic said, and the 10th Avenue project she champions will shortly grow from a $42 million repair job to a $100-million-plus replacement, probably accompanied by a lengthy closure.

That's just one span in Minnesota's large Road and Bridge Class of the 1970s. That class made it possible for a generation of Minnesota lawmakers to neglect transportation funding. And that class is about to make lawmakers and taxpayers pay a high price if they continue their habit of neglect.

Lori Sturdevant, an editorial writer and columnist, is at lsturdevant@startribune.com.