Wearing a new name, a new number, and grown fat with age, the waterway toll bill surfaced anew in a House subcommittee yesterday.

After being lost in the Capitol Hill shuffle since the Senate approved it last month, the bill suddenly lurched ahead on its seemingly endless path to passage.

When it was introduced, as the "Inland Navigation Improvement Act" (S.790), at the start of this 95th Congress, the waterway bill was a relatively lean piece of legislation.

Although the bill would make a historic change in federal transportation policy - imposing for the first time, a fee for commercial barge lines using federally maintained waterways - its sponsor, Sen. Pete Domenici (R-N.M.) had needed on five pages of legalese to set forth its provisions.

But then, for strategic reasons, Domenici had attached his proposal to a separate bill, the "Navigation Development Act," which is catch-all legislation authorizing dozens of the local water projects that members of Congress would like the federal government to construct in their districts.

Domenici believed this collection of "pork barrel" projects was the perfect vehicle for his waterway toll, because the pork provisions were favorites of the very members who most strongly opposed the toll idea.

Domenici turned out to be right.

When the "Navigation Development Act" finally came up for Senate passage last month, the measure had grown to 127 pages and was chock full of pork projects from southern Maine to Northern Mariana Island. To get all those projects, the Senate accepted a waterway toll as well (although a smaller toll than Domenici had pushed for).

But then the process had to start all over again in the House.

Although House members were willing to accept almost every water project authorized in the Senate bill, they considered it essential to pass a separate pork barrel bill of their own.

Some members were pushing for projects not included in the Senate bill. But even for projects the Senate had already approved separate votes were wanted, so that each House member could boast to constituents of having personally won approval of some favorite local levee or canal.

Accordingly, the water resources subcommittee of the House Public Works Committee yesterday opened four days of hearings to let the members file in and make their pleas for the projects on their shopping lists.

The committee has developed a complex formula to weigh the economic, environmental and engineering aspects of proposed projects, but yesterday's session suggest that loyalty to the overall pork barrel program can be important as well.

When Rep. Joe Rahall (D-W.Va.) stepped up to ask for a $100 million flood control project that cannot be justified under normal cost-benefit analysis, the subcommittee's ranking Republican, Don Clausen of California, told Rahall not to worry.

"We appreciate," Clausen told the young Democrat, "that you've maintained a voting record in support of other projects in other districts. We can probably help you."

As a result, the roster of water projects appended to the waterway toll bill seems sure to grow considerably by the time it reaches the House floor next month.

And that could improve considerably the bill's chance for enactment into law.

The waterway bill is in danger because President Carter is dissatisfied with the relatively mild tolls in the Senate version. In a press conference three weeks ago, Carter said he would veto the whole package, both toll and pork, unless the level is increased.

But congressional opposition to waterway fees in general is so strong that any significant increase seems unlikely. Thus many members are already counting on a veto - and counting the votes available to override it.

Each new pork project added to the bill means one additional member who might be willing to vote to override.

"I'm not all that worried about a veto," said Rahall after he made the pitch for his flood control project. "I think there's a good chance we'll override it. The committee's got - how many? - three more days of hearings.That's a lot more projects. And that's a lot more votes on our side."