[##_1L|1040330055.jpg|width="130" height="92" alt=""|_##]One weary week after the Interstate 35W bridge collapse, a senior federal lawmaker from Minnesota proposed sweeping legislation to establish a trust fund dedicated to repairing the nation's aging, deficient bridges. The proposal by Rep. Jim Oberstar (D-Minn.), chairman of the House Transportation Committee, would be aimed at repairing 73,784 bridges from coast to coast rated "structurally deficient" -- with a price tag that could be as much as $188 billion by one estimate. House Speaker Nancy Pelosi (D-Calif.) pledged to support the plan.

It could cost Americans dearly: the proposal includes raising federal gas taxes 5 cents from 18.4 to 23.4 cents, at a time when drivers are already reeling from high gas prices. President Bush and several prominent lawmakers have previously opposed gas tax hikes.

"If you're not prepared to invest another 5 cents in bridge reconstruction and road reconstruction, then God help you," Oberstar said, after touring the site of the collapse by helicopter.

Meanwhile, federal investigators seeking a cause for the accident zeroed inon two key factors that could not only explain the collapse but may also have implications for bridge safety nationwide.

One focus of the investigation now centers on how much concrete was on the bridge at the time of the accident and whether the bridge could sustain a load of new concrete as it was being resurfaced. Investigators also identified possible design flaws in "gusset plates" that connected the steel beams in a pattern on the bridge structure.

The concrete on the bridge surface had been poured during the 48 hours before the accident in ongoing summertime resurfacing, although none was poured on the day of the accident, according to National Transportation Safety Board sources.

The uncured concrete that was poured added weight to the bridge deck but because it had not yet set, it added no structural support, they said.

Investigators "obtained core samples of the bridge deck material to get a better picture of the deck thickness to help make an assessment about the amount of concrete on the bridge at the time of the accident," the NTSB said in a statement Wednesday.

As for the gusset plates, a weakness in the design when the bridge was built in the 1960s may have caused the bridge to fall under its load, investigators theorize.

"Safety Board investigators are in the process of verifying the loads and stresses on the gusset plates at these locations, as well as the materials used in constructing the gusset plates," the NTSB said.

Emotions remain high now with bodies still missing in the Mississippi River and a major investigation under way. But with Congress in recess, the ultimate fate of the legislation must await its return. It faces a balancing act with other priorities for spending, including costly wars in Iraq and Afghanistan.

"Last week, the country received a wake-up call with the collapse of the bridge in Minnesota. Our sadness must at least be met with a commitment to address our infrastructure shortcomings," Pelosi said in a prepared address to the National Conference of State Legislatures.

While Pelosi's spokesman, Brendan Daly, said the bill would "come to the floor quickly," its chances of passage are unclear.

Oberstar's chairmanship of the Transportation Committee, along with Pelosi's early endorsement of his efforts, boosts its odds of passing. With the tragedy fresh in their minds, lawmakers have made numerous comments about the need to tackle America's failing infrastructure.

But the measure faces serious hurdles, Congress-watchers say.

In a written statement, Minority Leader John Mica, (R-Fla.) called the legislation "a knee jerk reaction to the critical problem facing our transportation and infrastructure systems."

Thomas Mann, a senior fellow at the Brookings Institution in Washington, D.C., said the packed schedule the House is expected to face in September, combined with the proposed taxes, make it unlikely that Oberstar's legislation will succeed.

"Bush is utterly committed to vetoing any tax increases of any kind and Republicans in general remain opposed to this," he said. "This would probably require a Democratic president."

Estimates vary as to the cost of repairing all 73,784 structurally deficient bridges, but The Associated Press reported that the American Society of Civil Engineers estimates it would require spending at least $9.4 billion a year for 20 years, or $188 billion.

As the political debate swirled, searchers and federal divers worked nearly round-the clock and in painstaking detail to find at least eight people who remain missing. Authorities have mapped 88 vehicles in the river but did not say what was in them. Five people were confirmed dead in the last week and more than 80 injured.