With the prospects for Senate passage of his waterways toll bill, S. 790, looking brighter all the time. Sen. Pete V. Domenici (R.N.M.) turned late month to a rather fundamental problem he had ignored all spring: there was another house of Congress to worry about.

Domenici had steered his bill - which would establish, for the first time, a set of tolls for barges hauling freight on the nation's inland waterways - through two Senate committees, and lobbyists were reporting that it stood a good chance of victory on the Senate floor.

In the House of Representatives, though, the toll proposal was making less forward progress than a barge on a sandbar. The bill had been introduced by a junior member, Rep. Berkley W. Bedell (D-iowa), and promptly buried in a hostile subcommittee.

Domenici's Mission Impossible, then, was to find a means, in the Senate, to force his idea through the other half of Congress. By last week, he had a plan.

Article I, Section 7 of the Constitution establishes the requirement that a bill must be approved by both houses of Congress before it can be signed into law by the President. But that section doesn't explain how the two houses should work together to settle on a jointly acceptable form for each bill.

Over the decades Congress has developed the conference procedure, in which legislation that has been passed in similiar but not identical forms by the two houses is sent to a "conference committee" with representation from both Senate and House.

The conferees are charged with developing a single version of the bill which can be presented to each house for final passage. In most cases of dispute, each house yields partly to the other and a compromise bill is agreed to.

The possibility of a compromise is conference provided Domenici with the opening he needed. If the Senate were to pass his toll bill while it was still mired in the House subcommittee, he might still get the measure to the House floor by insisting on it a conference. And on the House floor, unlike the subcommittee to which it had been assigned, the waterway toll seemed to have a good chance of passage.

To employ that strategy, though, Domenici had to be sure he could get his measure to a conference. Since a waterway toll bill would probably never pass the House, and thus never reach a conference, the senator needed a vehicle.

Domenici had earlier found one to help his toll plan get through Senate committees. He had attached it to a bll authorizing a major new Mississippi River barge facility at Alton, III. But the Alton project was not sure of House passage, so the senator looked around for a safer bet.

The one he chose was S. 1529, a compendium of two dozen or so "pork-barrel" public works projects which had been lumped, for administrative convenience, into a single "omnibus" puplic works bill.

Because the onmibus bill contained goodies for almost every section of the country, it seemed sure to win passage in both house of Congress without much trouble. And because it included numerous waterway projects, it would be a perfectly logical place to append a proposal for a waterway toll.

The omnibus bill offered other advantages, too. Because it was a product of the Senate conferees on the bill would be chosen from Public Works members - who favor the waterway toll.

As a member of the Public Works Committee, Domenici would have a good chance to be appointed a conferee on the omnibus bill, so that he could personally push his waterway toll in the conference session.

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Acco [WORD ILLEGIBLE] decided [WORD ILLEGIBLES] his originalbill, S. 790, would be allowed to die.Instead, the senator would propose the waterway toll and its "sweetener," the Alton project, as floor amendments when the omnibus bill came up for a vote.

Whether the Senate would approve the toll plan was still uncertain. But if it did, Domenici knew, he now had a means to get it through the other half of Congress as well.