A bipartisan group of Senators who proposed an extension of the federal Production Tax Credit on Thursday. Proposing the two-year extension were Senators Chuck Grassley (R-Iowa), Mark Udall (D-Colo.), Scott Brown (R-Mass.), Tom Harkin (D-Iowa), Dean Heller (R-Nev.), Ron Wyden (D-Ore.), and Michael Bennet (D-Colo.).