When a Senate Appropriations subcommittee convened in the Capitol last July to consider the budget for federal buildings, there was little money included for new construction projects.

It wasn't long before the assembled senators noticed that $5 million had been slipped into the budget for an unspecified new building. No one knew any details of the project or how much it might cost, for it had never been reviewed by the Senate committee that approves such projects.

Yet everyone in the room knew what the money was for: a new headquarters for the Bonneville Power Administration in Portland, Ore. Everyone also knew that the project was a special plum for the home state of Republican Sen. Mark O. Hatfield, the new chairman of the Appropriations Committee.

No one rose to object to the Oregon project. But over the next few weeks it started a chain reaction in which a half-dozen other senators rushed to add another $29 million for their own pet building projects, a time-honored way of taking care of the folks back home.

From the moment President Reagan took office, 1981 was hailed as a watershed year in which a new president and Congress finally would bring the federal budget under control.

Many of the younger, more conservative senators, whose party had taken control of the upper chamber for the first time in a generation, led an unprecedented assault on domestic programs from welfare to food stamps.

But, while the country has been mesmerized with tales of these dazzling Reagan victories, some things on Capitol Hill have not changed. Many of these same senators have dipped into the "pork barrel" and pulled out a variety of parochial projects, making sure that new courthouses, dams, highways, inland waterways and nuclear plants continue to find their way into their home states.

As the 97th Congress begins its second year Monday, facing both Reagan's demand to cut another $30 billion in spending and a spiraling deficit that may surpass $100 billion, each of these public works projects may amount to little more than spare change. But their impact is dramatically greater back home, and together they add up to one more part of the budget that may remain untouched.

Sen. William Proxmire (D-Wis.) described the almost irresistible temptation to vote for more bricks and mortar.

"For a lot of senators, the question that's always raised against incumbents is: 'What have you done? You haven't done anything.' One thing you can point to that people can understand, see, touch, feel, is a public works project. Labor likes it, management likes it, it may even be named after you. Only the taxpayers pay for it--but the taxpayers in your district pay only a tiny fraction."

On some occasions, this is done with a degree of subtlety. There is, for example, no mention of the Bonneville Power building anywhere in the federal budget. Instead, the appropriations report that accompanies the budget says vaguely: "The committee has also allowed $5,000,000 and the necessary language in the accompanying bill for the advance design work for projects designated by the General Services Administration."

Said one committee staffer: "They didn't even have the guts to put it in the report."

All this came as a surprise to the people at Bonneville Power, where spokesman Bill Merlin said they knew nothing about the proposed project. Merlin said that, while the headquarters is overcrowded and staffers are scattered among six other locations, "we weren't clamoring for a new building."

Hatfield said in an interview that he had pushed the $77 million Portland building as a pilot project. "I had a very direct hand in that," he said.

The idea, Hatfield said, is to determine whether the GSA could make more accurate estimates of the eventual cost of a building by spending more money on an advanced design.

"It just happens to be a building I'm interested in," he said. "If I had wanted to exercise political power, I could have found some way to put Bonneville in there and push through some construction money as well."

The art of getting a federal building used to be more straightforward. For years, the Senate Environment and Public Works Committee approved dozens of federal buildings and courthouses at a time, even though the members said they knew little about each project or how the money would be spent.

As a result, the committee found, a flurry of unneeded buildings were constructed at a cost two and three times the government's estimates. Many of these projects were poorly planned and poorly constructed: a new courthouse in Honolulu was flooded by the Pacific Ocean; a federal building in Philadelphia began to sink slowly into the ground.

The new chairman of the public works panel, Robert T. Stafford (R-Vt.), and a key Democratic member, Daniel P. Moynihan of New York, have been trying to spoil the fun by refusing to approve any new buildings until the most blatant pork barrel practices are eliminated. They say they are determined not to build more wasteful projects simply because they are sponsored by influential members of Congress.

But they're fighting an uphill battle--a project that might be considered an embarrassing piece of pork in Washington often brings favorable headlines back home.

Even Moynihan, while leading the call for reform, has pushed through a Social Security building in Queens and the massive Westway highway project in Manhattan. A senator may not get much publicity for his backstage role, an aide to Moynihan said, "but the local politicians know who is delivering for them in Washington and who isn't."

The senators who can deliver the most are those on the Appropriations Committee, where they have learned how to sidestep the public works panel by garnering support for their favorite projects at budget time.

Hatfield, a thoughtful, moderate Republican who has opposed some of the Reagan administration's cuts in domestic programs, is not an especially ardent practitioner of pork barrel politics.

In fact, he pales in comparison to his Democratic predecessor, former senator Warren G. Magnuson of Washington, whose state seemed to have an open pipeline to the Treasury during the years that he presided over the Appropriations Committee.

All Magnuson had to do was mumble a few words about an amendment and pound his gavel, and millions of dollars would be approved to develop the Seattle waterfront or build a new trolley line or clean up after the eruption of Mount St. Helens.

President Kennedy is said to have remarked, "It is a wonderful thing about Maggie--he stands up on the floor and goes burble, burble, burble, and the next thing you know you have the Grand Coulee Dam."

Hatfield once felt the brunt of the chairman's power when, having had the temerity to oppose one of Magnuson's bills, he found that a public works project for Oregon had suddenly disappeared from the budget. It reappeared just as suddenly when Hatfield discovered a long-forgotten speaking engagement at an obscure college on the day of the vote, which Magnuson won by a single tally.

But while the easy-going Hatfield disdains that sort of arm-twisting, he seems more than willing to perpetuate the pork barrel system he inherited. It was, after all, his Portland project that became the first in a series of additions during that subcommittee markup in July. Sen. James Abdnor (R-S.D.), for instance, soon made sure that another $4 million was included for additions and improvements at the Denver mint.

Many senators in the room were puzzled, since the project had no apparent connection with Abdnor's state. When Proxmire questioned the need for the money, Abdnor, who chairs the subcommittee that oversees the Treasury Department and all public buildings, insisted that the work was necessary. "I want this project," he said.

What Abdnor's colleagues didn't know is that the new director of the Denver mint, Nora Hussy, was the Republican National Committee member in South Dakota and a key supporter of Abdnor in the 1980 election.

"I got a call from Nora on it," Abdnor said in an interview. "She told me it was needed. The fact that this lady is from my state is not the principal reason, but . . . . "

Abdnor said one of his staffers went to Denver and concluded that the mint would not be able to make enough coins unless the improvements are made. He said the project, which eventually will cost $12 million, actually will save money because Hussy wanted to put up a new building for the mint instead. "This is nothing but a repair job," he said.

Abdnor's $4 million addition succeeded in angering some of the other senators who had been willing to wait for their projects to clear the standard hurdles. For example, Sen. Barry Goldwater (R-Ariz.), the elder statesman of the conservative movement, and Dennis DeConcini (D-Ariz.), who serves on the Appropriations Committee, had been pushing for a new immigration station for their state.

Last May, when the pair took to the Senate floor to push an amendment to fund the border station, several observers said Goldwater seemed uncomfortable in his new-found role.

"What we are asking for is $6.8 million," Goldwater told his colleagues. "It is not a lot of money when you look at the entire cost of the bill . . . . It gets dropped, I think mainly, because San Luis is on the Mexican border in a rather forsaken part of that border."

The Republicans staged a roll call as a delaying tactic while the two Arizona senators huddled privately with Stafford and Moynihan. DeConcini asked if the public works panel at least could approve some money to start designing the border station. Stafford said that would be unfair to others who were waiting for their projects, but that he certainly would try to approve the border station next year. Goldwater and DeConcini threatened to push for a vote on their amendment. Stafford and Moynihan said they would work to defeat it.

"It was like a poker game," one participant said. "The question was who would fold first. They kept saying, 'Look, it's only $6 million.' Around here, that's pocket change." Finally, the Arizonans backed down and withdrew the amendment.

But two months later, when Abdnor added money for the Denver mint, DeConcini decided he and Goldwater were getting shortchanged. "Listen," he told one colleague, "if he's going to put in this Denver mint project, I'm going to try to put in the border station." DeConcini offered the amendment and Abdnor agreed.

Stafford was upset that his public works committee was being ignored in what he said was a clear violation of law. In a "Dear Mark" letter to Hatfield, he complained that his committee "has never received any request for authorization of funds for the Denver mint or the Bonneville Power Administration." Hatfield later told Stafford that he understood but could not go along.

That, however, was just the beginning. When the full Appropriations Committee met on Sept. 15 to take up the budget, several other senators were ready with their own amendments.

Sen. Strom Thurmond (R-S.C.) is usually not a fan of increased federal spending, but he and Ernest F. Hollings (D-S.C.) had been pushing for a new annex to the federal courthouse in Charleston. Aides to the senators had escorted U.S. District Court Judge Sol Blatt Jr. around Capitol Hill in July as he lobbied for more space for the courthouse, which he said was overcrowded with drug cases. Hollings' former law partner, Judge Falcon B. Hawkins, made the same arguments from Charleston.

During the markup session, Hollings asked his colleagues on Appropriations to include another $5.4 million to expand the Charleston courthouse.

These public works projects tend to have a certain bipartisan appeal. Sen. Paula Hawkins of Florida, a newly elected Republican, rarely agrees with veteran Sen. Lawton Chiles (D-Fla.), but both have been pushing for a new federal building in Tallahassee. The building would be built at public expense by private developers, who would then rent space to various federal agencies.

A spokesman for Hawkins said that "she is a cost-conscious senator, but there was a critical need for this building. This is a move for efficiency because federal agencies are now scattered all over Tallahassee." Since Chiles sits on Appropriations, he asked the committee to add $738,606 toward the building this year.

Sen. Walter D. Huddleston (D-Ky.) then asked that $8.3 million be added for a new courthouse in Ashland, Ky. The committee voted to include money for all these projects.

Huddleston also helped out a fellow Democrat by moving to include a $44 million federal building in Omaha for which Sen. Edward Zorinsky (D-Neb.) had been lobbying vigorously. Zorinsky is not a committee member, so the panel approved only $4.5 million to buy the land and design the building.

"They saw it was getting kind of porky," one staff member said.

When they were done, six new projects had been added, and every one except Zorinsky's had been to accommodate a member of the committee. In past years such projects had simply sailed through the public works panel, but now their sponsors were forced to resort to the appropriations process.

Each senator had a long list of reasons why his state needed a new building, but the net effect was to more than double--to $57 million-- the size of the construction budget.

Still, the game wasn't over yet. There was one final building that no one in the Senate particularly liked--a new federal courthouse for Redding, Calif. This particular courthouse seems somewhat unusual, for there is no federal judge assigned to Redding. And the other major tenant for the building, the Agriculture Department, has said it doesn't need the extra space.

The building had been pushed through by a former House Public Works Committee chairman, Harold T. (Bizz) Johnson (D-Calif.), who gained local notoriety for helping to turn Union Station into a waterlogged visitors center. Even though Johnson was called home by the voters in the last election, his House colleagues added $12.8 million to their budget for the courthouse that would commemorate their former chairman.

When the two bills went to a House-Senate conference, some House members suggested that if the senators wanted their half-dozen extra projects, they would have to accept the Bizz Johnson building. The senators reluctantly agreed.

As the congressional session came to a close just before Christmas, a subdued Hatfield sat in his office and reflected on how the public buildings budget had gotten out of control.

"If anyone should take the rap on that, I should," he said. "I didn't want Bonneville to become a Christmas tree or some excuse to hang these other projects on.

"I should have done more to block that from happening. I was busy with other things, and it's awfully hard to follow the details in 13 subcommittees. But I probably could have done more than I did."