SRS, you are correct and I was wrong.
The Skagit is still classed as a navigable stream. The Corps of Engineers has a role because waterworks are involved, also the Coast Guard.

Funds will probably come from DOT, if the fix is declared an emergency.

The U.S. Corps of Engineers produced a flood reduction and ecosystem restoration feasibility study in 2009.
They can ask for restriction of flow from the dams.

Skagit County has 108 bridges, 42 are 50 years old or older. (Skagit County Public Works Dept.)

The U.S. Dept. of Transportation (DOT) says it has funds to rebuild. $1,000,000 in emergency funds authorized.
"Scenarios" for repair or rebuild are being considered.
DOT has sent their chief engineer to inspect the span.

Washington's governor says cost to fix will be $15 million. Repair probably will be the outcome.

A good summary- Seattle Post Intelligencer:
http://blog.seattlepi.com/seattlepolitics/2013/05/24/federal-available-to-repair-skagit-sec/lahood/