A proposed $46 million memorial to Franklin Delano Roosevelt, envisioned as a 1,000-foot garden wall along the western end of the Tidal Basin, is coming under public and congressional scrutiny this summer for the first time.

The proposal, the fourth since Congress authorized a major FDR memorial in 1955, was officially presented to congressional committees last week - with a color film and a 67-page book on the design - and will be discussed at public hearings in September.

The plan is virtually the same as a design by San Francisco landscape architect Lawrence Halprin that was approved in 1975 by the FDR Memorial Commission, the Fine Arts Commission and the National Capital Planning Commission (NCPC). However, the original plan included a 1,400-foot-long garden wall, with a cost estimate of $20 million.

The final design, which includes four major sculptures, waterfalls, roses and woodsy landscaping, was approved this spring by the Fine Arts Commission and was given an unofficial blessing from the NCPC. The planning commission cannot give final approval until public hearings are held and an environmental impact statement is completed by the National Park Service.

If Congress approves the funds and the proposed memorial passes environmental and public reviews, it would be built in about four years or just in time for the centennial of Roosevelt's birth in 1982.

The design centers on a 14-foot-high, meandering, reddish-granite wall, with four major alcoves or rooms for the sculptures, a small visitors' center, a theater, museum and restaurant. The memorial would be set back from the cherry trees along the Tidal Basin, following the western edge of the basin along what is now West Basin Drive. In addition, a grassy "berm," or hill, would hide the wall from the playing fields that stretch nearly to the Lincoln Memorial.

The wall, to be inscribed with quotes from FDR, would have water running along or cascading over most of its length and would fill the air with the rushing sound of water, said John Parsons, who is coordinating the project for the Park Service.

The noise of the waterfalls is not just to remind visitors of Roosevelt's many associations with water - sailing at Campobello, his term as Secretary of the Navy in World War I and swimming in the healing waters of Warm Springs, Ga. - but also to muffle the sounds of jets from National Airport.

"The noise levels in West Potomac Park reach 90 decibels every 55 seconds, as the jets go by," says Parsons, "and the water will be what is called white noise" to make the jets less noticeable.

Despite its length, the memorial is designed to be unobtrusive, not a monolithic memorial competing with the nearby monuments to Lincoln, Jefferson and Washington. But it is meant to be slightly more obstrusive than the existing FDR memorial on Pennsylvania Avenue, a desk-size stone block in keeping with Roosevelt's wishes.

Roosevelt once told Supreme Court Felix Frankfurter that if there were to be a memorial: "I know exactly what I should like it to be . . . a block about the size of this touching his desk, placed in the center of that green plot in front of the Archives Building."

Two larger memorials have been proposed since Congress established the Roosevelt Memorial Commission in 1955. The first, dubbed "instant Stonehenge" by critics, called for eight concrete slabs in West Potomac Park. The second included eight, huge granite darts surrounding a 32-foot granite cube. Both were approved by the Roosevelt Commission but rejected by the Fine Arts Commission. A third proposal, a rose garden in West Potomac Park, was dismissed as not monumental enough.

If the current proposal is approved, one effect would be the elimination of some playing fields in West Potomac Park and the elimination of part of West Basin Drive, popular with tourists coming to the Tidal Basin to see the cherry blossoms.

While the memorial would take land beside the Tidal Basin, Parsons said, several new playing fields are being created along the south side of the Reflecting Pool, where the Folk Life Festival was held for several years. More than 500 ball teams paly softball, football, soccer, cricket and field hockey on Park Service playing fields.

Motorists will still be able to circle the Tidal Basin under the proposed raod plan, but would have to make a wider circle on the west along the river's edge.

Parsons said the estimated $46 million cost may seem high - more than 40 times the cost of the Washington Monument and 10 times more than the Lincoln and Jefferson memorials. He noted, however, that the Washington Monument, which cost $1.1 million when it was completed in 1885, couldn't be built for less than $45 million today. He added that the Lincoln Memorial, which cost $3 million in 1922 would cost almost $60 million today, and the Jefferson Memorial, built for $34 million in 1943, would take an estimated $38 million to build now.