A half-dozen mini-playgrounds, with more in the works, are sprouting up at U.S. job sites around the National Mall as Uncle Sam pushes to provide more on-site day care for federal workers in the city.

Nestled between the massive neoclassical buildings that house federal agencies and line Independence and Constitution avenues NW, the small grassy areas replete with jungle gyms and sandboxes are changing the character of the city's sterile monumental core to include play space for more than 500 preschoolers.

"We're definitely in a growth spurt right now, because there was so little existing," said Diane Savoy, child-care coordinator for the national capital region at the General Services Administration.

D.C. law requires day-care centers to provide daily outdoor playtime for their charges, weather permitting.

And while dozens of U.S. agencies line the largest open space in the city, the mall's busy streets and absence of play equipment preclude its use for daily outings.

So, agency after agency has come forward to propose creating playgrounds on site.

Last month, the Federal Trade Commission opened a $10,000 outdoor play area for 40 children near its building at Sixth Street and Constitution Avenue NW.

In June, a $320,000 facility at Walt Whitman Park opened along E Street NW between 19th and 20th streets to serve 140 youngsters from centers at five nearby agencies.

The Department of Defense built the largest facility, a wood-fenced 1.1-acre fairyland of climbing equipment for 200 youngsters across from the Pentagon.

And three more, to serve an additional 236 children, are on the drawing board to go up in the next several months: At the Department of Agriculture at 14th Street and Independence Avenue SW, at the Deparment of Energy at 10th Street and Independence SW, and at the Department of Health and Human Services at Third Street and Independence Avenue SW.

Last month, officials at the National Capital Planning Commission, concerned about the flurry of proposals, asked the GSA to begin setting some standards for air quality, traffic levels and access to the play facilities.

"We're asking for some concentrated study," said Joe Mansias, director of intergovernmental and public affairs for the commission. "If there's going to be a proliferation {of outdoor play areas}, shouldn't we have some guidelines?"

Until now, the GSA has submitted proposals to the commission as agencies have asked for them. "To give this some kind of understanding and cohesion, {the GSA} should take a comprehensive look," said commission spokesman Leigh Feldman.

Savoy said the GSA measures noise, pollution and traffic levels against national standards but has no checklist for every proposal.

"The approach that we take is to try to get agencies to work together" to pool their resources, she said.

But even if they do, Savoy predicted the number of child-care centers -- and corresponding outdoor playgrounds -- will continue to spiral upward.

"The need has always been there," she said. "It's just that there has been more attention paid to that need."

Day-care center staff members say the attention is long overdue. Playgrounds, they say, provide needed stimuli for physical and emotional development that walks around the city or mall simply cannot provide.

"There's just no comparison; we had no place to play," said Pam Simon, director of the GSA facility. "Teachers got very creative at using the space available, but there was nothing designed specifically for them."