There must be a lot of smiles around Vermont’s capital city of Montpelier these days. And not just because the holidays are around the corner, or the fall leaves were particularly attractive this year.

Earlier this month, the Vermont Agency of Transportation (VTrans) announced that repairing road, bridge, and culvert damage inflicted by Tropical Storm Irene on August 28 will total between $175 million and $250 millionless than half of the initial forecast of $620 million.

The higher estimate wasn’t difficult to accept, given the dramatic images of damage (including those in this VTrans presentation) created when Irene’s 8- to 11-inch downpour overwhelmed waterways still swollen from rains of previous weeks.

At one point, VTrans reported that more than 531 miles of state-owned highway, including 34 bridges, were out of service. The local road system was also a patchwork of closures, with 175 segments and 90 bridges closed.

After two months of intense construction, only 10 miles of state highway and two bridges remained closed. Restoration of local roads has been slower, with 131 road segments and 77 bridges still  out of service. 

So why such a huge discrepancy in cost estimates?

According to Gov. Peter Shumlin (D) and VTrans officials, the agency’s engineers used standard construction practices to estimate costs, which typically include things like permitting, utility relocation, environmental mitigation, design reviews, right-of-way acquisition, etc.

The costs were subsequently recalculated using the Federal Highway Administration’s Detailed Damage Inspection Report (DDIR) process, which is tailored to provide a preliminary estimate of repairing disaster-related damage.

There was no mention of how and when the discrepancy was found. But despite the markdown, the final pricetag for rectifying Irene-related damage is still a moving target, and all but certain to exceed the state’s entire $181.8 million share of its FY2012 transportation budget (currently projected at $553.6 million).

That’s why, almost from the time Irene lumbered its way into Canada, state officials have been looking to Washington for help.

So in a rare example of “ask and you shall receive” in the current gridlocked Congress, negotiators agreed Monday to free up federal funds for Irene-related damage. With $1.662 billion added to the FHWA’s emergency fund to cover Irene’s damage along the East Coast, and the removal of what had been a $100-million cap on federal assistance for those projects, Vermont will be better able to move past the nightmare that was Irene without a corresponding dent in its budget.

That’s great news for the Vermont’s taxpayers and travelers, but it also raises the question of what might have happened had the error in calculating disaster damage not been found.

Using the original estimate, State officials would have faced a more far-reaching nightmare of project cutbacks. And generous Congressional negotiators might have OK’d a larger outlay of federal disaster funds.

(I doubt anyone in Vermont would want to relive the trauma of Irene by having its infrastructure repairs in the company of other real and Internet-inflated examples of alleged federal overspending, particularly in the current hyper-charged political environment.)

Yes, there are a lot of smiles in Montpelier fall. And, probably, more than a few sighs of relief as well.