The trash has all been carted off, the pigeon droppings scraped away, the floors and walls repaired. Today the Washington Project for the Arts, which last June lost its G Street home, begins showing art again.

The WPA -- a kind of artist-run museum -- has moved to 400 Seventh St. NW. Two good shows of local art open there today. But the most impressive works on view are the galleries themselves.

They are vast, wood-floored, white-walled, well-lit. The WPA's new third-floor gallery -- now showing "First Viewing: New Photographers in Washington" -- has 17 large windows and 4,200 square feet of floor space. The second-floor gallery, where Robert McCurdy's huge new paintings hang, is smaller but as sunny. Three months ago these spaces, derelict for years, were piled high with plaster, dead birds, dustballs, junk. The change has been amazing. And -- because artist volunteers did much of the work -- amazingly inexpensive.

Neon artist Robert Dick did wiring and painted. Sculptors Charles Sleichter, Suzanne Codi and Chris Gardner built the wood reception desk. Crews of Job Corps workers, training with the National Association of Home Builders, labored there as well. Earlier this week, painter Mike McCall, coated with fresh sawdust, coughed and grumbled as he sanded down the bookstore floor.

"Believe it or not," says Al Nodal, the WPA's director, "the entire three-floor renovation, including the new bookstore and offices for the staff, cost $16,000."

Nodal, a master scrounger, received many gifts -- lumber from the Artery Organization, plywood from Georgia Pacific, wallboard from Metro Building Supply Co., sheetrock from U.S. Gypsum, paint from the Silver Paint Co. and electrical equipment from the Truland Corp. That's just a partial list.

"We only buy what we can't get for free," says Nodal. "We depend upon our friends."

When Nodal became director in 1978, nearly 50 percent of the WPA's annual operating budget of $70,000 came from government grants. "We got a running start," he says, "from the National Endowment for the Arts. Now we're on our own." Last year's operating budget was $317,000. Of that amount, 84 percent came from private-sector gifts.

During its move to Seventh Street, the WPA has not been quiescent. The neon show now on view at locations throughout downtown is a WPA project. In addition to its in-house shows, its performances and concerts, the WPA in recent years has placed 40 outdoor works of art in Washington's public places.

WPA's Seventh Street renovation is not yet complete. A new atrium exhibition space for large, special installations -- and a 200-seat first-floor theater for performance art and music, video and dance -- is scheduled to open in the spring.

"Two years ago I was really worried about the WPA's future," says Nodal. "I'm not worried anymore."

The WPA is run for artists, by artists. The McCurdy exhibition, like many others held there, gives a gifted local painter his first local one-man show.

Viewers who believe that some sort of chasm yawns between wholly abstract color-field painting and representational portraiture ought to see McCurdy's work. His paintings bridge that gap. A meticulously rendered, lifelike and life-size woman (Graziella Guerra, the wife of the artist) stares out from each one. Behind her floats a dappled field of open, airy color. The viewer who's accustomed to reading abstract painting is pulled into another, different kind of seeing by the portraits encountered in McCurdy's art.

Photographer John McIntosh, who organized "First Viewing: New Photographers in Washington," sees most Washington photographers as complacent, out of step, unoriginal, inept. The viewer may well wonder why he finds the 12 artists he has chosen so much better than their peers.

The show is a mixed bag. Two of the photographers -- Tom McGovern and Benjamin F. Boblett -- do the straightest sort of portraits. William Carter, for the most part, does straight photojournalism, though one of his pictures -- of a Black Muslim comparing Ronald Reagan to the Beast of Revelation -- is a work with bite. Carol Harrison Grady not so long ago made the straightest sort of still lifes, though the 19th-century formalities that used to rule her work have, in her newest pictures, begun to dissolve.

A number of these artists do not fear affectation. Mark Holmes' models play with fire and with water and like to vamp about in operating rooms; his color photographs recall the kinky chic now used to sell fancy clothes in fashion magazines. Somewhat more amusing are Joseph Gordon's color shots of body parts adorned with icky colored foam.

Two artists in this show -- Kevin MacDonald and James Sherwood -- make drawings of their photos, and it is refreshing to see their photographs and pencil works side by side. G. Michelle Van Parys' gum bichromate prints are also well worth seeing, though her work, and that of Joseph Mills, perhaps relies too much on the abundantly familiar traditions of collage.

The most memorable pictures here -- those by Robert J. Gurfinkel and Jannette Shelly -- are not particularly daring. They're just good. Gurfinkel's densely composed outdoor shots are spiced with the bizarre: a lamp appears upon a lawn, an umbrella has been placed in a chain-link fence, a globe rides on a bicycle. Shelly's color photographs of pets and people and interiors are wonderfully unforced; they are snapshots of a sort, except in their colors, which are carefully considered, subtle and most rich. A 12-print portfolio accompanies the show; it costs $45. The McCurdy show closes Dec. 12, the photo exhibition on Dec. 31.