The Senate today rejected an attempt to expand offshore drilling and approve the Keystone XL pipeline as it worked through a tall stack of amendments to the $109 billion transportation reauthorization bill.

By 4:30 this afternoon, senators had voted on 12 amendments, rejecting one that would have extended some energy tax incentives and another that would have offered incentives for natural gas vehicles. The chamber has 10 amendments to go before it can vote for final passage of the two-year surface transportation bill (S. 1813).

By a vote of 41-57, the Senate rejected an amendment from Sen. Pat Roberts (R-Kan.) that aimed to expand domestic energy production by requiring oil and gas leasing in the Arctic National Wildlife Refuge and in now-protected parts of the Atlantic and Pacific oceans.

The amendment echoed several measures that were also rejected by the Senate in a series of votes Thursday -- including approval of the Keystone XL oil sands pipeline -- but combined them with language retroactively extending a small group of energy tax credits.

Roberts had said before the vote that the bill was necessary to boost supply and bring down gasoline prices, but Democrats objected to the expanded drilling provisions.

The amendment's failure also meant federal employees face one fewer threat to their pay, which lawmakers have repeatedly targeted to offset the cost of unrelated programs. Roberts' provision would have added an extra year to the current federal salary freeze, which is scheduled to expire at the end of this year. The savings would have helped fund the extension of expiring tax incentives.

Before today's vote, Sen. Ben Cardin, a Maryland Democrat whose district includes many federal employees, chastised colleagues for "picking on the federal workforce." Already Congress has increased pension contributions for new federal employees, and the House's version of the highway bill would go further by making retirement more expensive for the entire federal workforce.

Senate leaders expressed optimism they could get to final passage of the transportation measure today. The bill had 85 "yes" votes for an initial cloture measure, and senators are confident there'll be bipartisan support for the legislation once the amendments are dispensed with.

Tax extenders, NAT GAS

The Senate also rejected an amendment from Sen. Debbie Stabenow (D-Mich.) that would have extended more than a dozen energy tax credits, including a production credit for wind and solar power that has backing from several Republicans and renewables groups.

The amendment failed to meet the 60-vote threshold, failing on a 49-49 vote. Renewables groups bemoaned the defeat, with Advanced Ethanol Council Executive Director Brooke Coleman saying the Senate had "missed an opportunity to put to bed the pressing need to extend expiring tax incentives for cellulosic biofuels and other sources of domestically produced clean energy."

Sen. John Thune (R-S.D.) said before the vote he'd like tax extenders to come up in one package, rather than in individual pieces.

Likewise, an amendment from Sen. Jim DeMint (R-S.C.) that would have scaled back some of the same energy tax credits was rejected, 26-72. That amendment would have rolled back tax credits for oil, gas, renewables, nuclear power and biofuels, while also targeting two oil and gas credits opposed by the White House.

The Senate also voted down a controversial bipartisan amendment that would have extended incentives for natural gas vehicles.

The "NAT GAS Act" from Sens. Robert Menendez (D-N.J.) and Richard Burr (R-N.C.) would have raised tax credits offered for natural gas cars and trucks and offered incentives for fueling infrastructure.

The language -- which drew fire from conservatives who said it was an unfair market incentives -- garnered 51 yes votes but failed to meet the 60-vote threshold.

Before the vote, a broad group of environmental and fiscal-conservative groups -- including Taxpayers for Common Sense, Friends of the Earth, Greenpeace and the Heartland Institute -- sent a letter to the Senate urging a rejection of the NAT GAS amendment. The bill, they said, "interferes in the marketplace to favor natural gas over other transportation and energy technologies that may be more cost-effective or sustainable."

Speaking before the vote, Menendez said the amendment would "jump-start" the natural gas transportation market, adding that it was necessary to boost alternative fuels. He said the bill would have been paid for with a user fee on natural gas, reducing its budget impact.

The amendment did draw considerable support from Democrats, and supporters say it's possible the language will return in some form.

Germane amendments

Having cleared a list of nongermane amendments -- many dealing with energy issues -- the Senate moved on to its list of 18 germane amendments. Earlier in the day, the Senate rejected language from DeMint that would have devolved federal funding to the state level, a move that many warned would essentially ruin the bill.

The DeMint amendment -- which failed 30-67 -- would have allowed states to keep much of the gasoline-tax money and would have devolved several federal transportation programs.

Another amendment from Sen. Dan Coats (R-Ind.) about the amount of funds distributed to certain states also failed, 28-70. The provision would have distributed money to states based on the percentage they pay into federal coffers, and Coats argued before the vote that it would have required "fairness in the distribution of funds."

Sen. Barbara Boxer (D-Calif.) fought that amendment, saying that it would "jolt" states during a difficult economic time and that it would essentially kill the underlying reauthorization language.

A provision from Sen. Rob Portman (R-Ohio) that would have allowed some states to opt out of federal programs was also defeated.

On a voice vote, the Senate approved an amendment from Sen. Jeff Merkley (D-Ore.) that loosened some restrictions on agricultural transportation. Another from Sen. Sherrod Brown (D-Ohio) expanding Buy America provisions also passed on a voice vote.

Also approved was language from Sen. Roy Blunt (R-Mo.) that would offer a funding stream for nonfederal aid bridges.

And another voice vote approved an amendment from Sen. Amy Klobuchar (D-Minn.) that would set restrictions for drivers transporting agricultural products.

An amendment from Sen. Jeff Bingaman (D-N.M.) that prevents privatized highways from netting federal highway distribution money passed, 50-47. Republicans argued the amendment took too much power from states, but Bingaman said it merely shifted money away from roads already getting private funding.

Reporter Emily Yehle contributed.