With a timely tug from Tip O'Neill the barge toll bill, S. 790, slipped past a potentially lethal parliamentary obstacle last week and semed, all of a sudden, to be in line for quick approval in the House of Representatives.

It was a remarkable turnabout in the fortunes of the bill, which had appeared, just two weeks ago, to be facing an insurmountable constitutional problem.

The legislation, which would require barge lines to pay a fee for their use of federally built and maintained inland waterways, had squeaked through the Senate late in June and been sent to the House.

But the House's chief tax writer, Ways and Means Committee Chairman Al Ullman (L-Ore.), took one look and raised his furry eyebrows.

The waterway fee would, of course, produce revenues. That made S. 790 a "revenue bill". Al Ullman knew that the Constitution specifically states that all revenue bills must originate in the House. SO Ullman began hinting that S. 790 might be a candidate for a "blue slip" - the form notice the House sends the Senate when it finds that the Constitution's "origination clause" has been violated.

A blue slip would have killed S. 790. That prospect dismayed proponents of the waterway fee. It also caused consternation in the barge industry, which opposed the fee but strongly favored another section of the bill that authorized construction of Locks and Dam 26, a major new barge facility on the Mississippi.

Accordingly, friends and foes of the Waterway toll began searching for a compromise that would avoid the blue slip. Inevitably, their search led them to Rep. Thomas P. "Tip" O'Neill (D-Mass.), the Speaker of the House and a compromiser par excellence .

Personally, O'Neill was inclined to let the Senate bill move on to a House vote For one thing, his close friend. Brock Adams, the Secretary of Transportation, was pushing hard for the waterway fee. For another, the Speaker wanted to clear away as much pending legislation as possible so the House could get down to uninterrupted work on the White House energy package.

Professionally, however, O'Neill felt he could not let S. 790 go unchallenged.

Like Winston Churchill, who declared that he had "not become the King's First Minister to preside over the liquidation of the British Empire," O'Neill wanted everyone to know that he had not become Speaker to stand by while the Senate violated the House's constitutional prerogatives.

O'Neill conferred with Adams. He hudled with ullman. He chated with 'Harold T. "Biz" Johnson, the California Democrat who chairs the Public Works Committee. And last week, in a meeting with all the principals, the Speaker spoke.

To avoid the origination problem, O'Neill said, the House would have to originate its own version of S. 790. Johnson's committee would approve the locks and dam project. Ullman's committee would write a waterway fee bill. The two measures would be linked on the House floor, passed, and sent to the Senate.

It had taken the Senate five months to achieve all that, but O'Neill said he couldn't wait that long. The two committees were to finish their work by July 25. The full House would vote a day or two later. By Aug. 1 - when O'Neill wanted to start debate on the energy bills - the waterway toll would be back in the Senate.

With both Adams and the barge industry backing that proposal, the Speaker's tight timetable seemed likely to be met. Both committees immediately scheduled hearings and "markup" sessions for this week, and all concerned were predicting that the bill would move through the House almost precisely the way O'Neill programmed it.

The problems, if there were any, lay in the Senate. With a new waterway toll bill coming over from the House, the Senate would have a vote on the measure a second time. Would opponents of the toll try again to defeat it?

Apparently not, according to Sen. Russell Long (D-La.), who had been the bill's leading Senate adversary.

"There's only so long you can drag these things out," Long said in his gentle bayou twang. "We tried to beat this bill once, and we lost. Not by much, but we lost. We're not going to get anywhere trying to do it again."

For the present, at least, there was smooth sailing ahead for the waterways bill.