The Senate began debate this morning on the $7 billion rescue of the nation’s highway trust fund that was passed by the House late yesterday, with four GOP amendments slated for a vote.

The first proposal, from Sen. David Vitter (R-LA), would replenish federal highway programs with unused money from the $787 billion economic stimulus law, as opposed to funds from the general Treasury.

Vitter began by echoing a lament of many sustainable transport advocates — that the stimulus spent a paltry 3.5 percent on infrastructure — but came to a far different conclusion: "[L]et’s do real concrete shovel-ready projects," he said. "Let’s build roads and highways and bridges."

Sen. John Ensign (R-NV) offered an amendment similar to Vitter’s, suggesting that un-obligated stimulus money offset the estimated $7.5 billion in unemployment aid that is attached to the highway trust fund fix.

Another similar proposal was filed by Sen. Jim DeMint (R-SC), while a technical tweak to highway contract authority was filed by Sen. Kit Bond (R-MO). Stay tuned for updates on today’s votes.

Late Update: The Senate has officially passed the $7 billion patch by a vote of 79-17. All four GOP amendments failed — although Vitter’s snagged two Democratic votes, from Sens. Ben Nelson (NE) and Blanche Lincoln (AR).