The D.C. Zoning Commission may extend for six more years the deadline for closing all parking lots in SP zoning districts, a ruling that would have a heavy impact on the Dupont Circle and Judiciary Square areas.

SP zones are designed to contain residential and commercial properties to protect established neighborhoods from commercial establishments. The zoning commission adopted regulations in 1978 that prohibited landowners from opening any new parking lots in SP zones and set a four-year deadline for phasing out existing lots. In 1983, the commission extended the deadline to six years.

Now the city's Office of Planning is proposing that the deadline be extended an additional six years. The zoning commission is expected to vote on the proposal at its regularly scheduled meeting in September.

Nathan Gross, chief of zoning services for the planning office, defended the proposal before the zoning commission, saying that the extension was necessary to keep undeveloped land in the SP zones from being turned into vacant lots.

"We originally thought the market would bring development to many of these lots four years ago, but the market has been slow in some areas," Gross said. "Six more years would be a long enough period to see a change in development conditions that would allow the parking lots to terminate and other development to occur."

At least one citizen's group, Residential Action Coalition from the Dupont Circle area, protested the extension, however, saying that the continued existence of parking lots in the SP zones undermines the zoning commission's original compromise with citizen groups, and that parking lots create a "blighted" environment in areas that are supposed to protect residential neighborhoods from commercial development.

"Although the original concept for the SP zone was that it was supposed to have a mix of residential and commercial, only one development built in a SP zone since 1958 has had residential in it," said Harriet Hubbard, president of Residential Action Coalition. "All the residences have been driven out by the existing parking lots."

James H. Blondell, a spokesman for the Washington Parking Association, said his organization supported the extension, but would rather see the phase-out lifted entirely from the zoning regulations.

"We don't think parking lots need to be phased out of the SP zones," Blondell said. "If they are going to, however, they should grant this extension . . . because the public is better served by having a parking lot in an SP zone than a vacant lot. No one benefits when a lot sits vacant for a long time."

There are approximately 20 parking lots in SP zones in the city at this time, most of which are concentrated along Massachusetts and New Hampshire avenues near Dupont Circle, along Massachusetts between Scott Circle and Mount Vernon Square, and in the area around Judiciary Square.

Although the planning office favors the six-year extension, it also outlined three other options for the zoning commission, including adopting a new regulation that would phase out only parking lots in the SP zones that were within 1,000 feet of a Metrorail station. The planning office suggested that those parking lots be given 12 years from the day the Metro station opened before they would have to close.

The other options would be to allow parking lots in the SP zones, or to allow them only if there is a "legitimate" need for parking at that site.

"We would like to leave some pressure on sites to redevelop in a reasonable amount of time," said Gross, explaining why the planning office supported the six-year extension. "The whole controversy about leaving these parking lots open will be rendered moot in the next few years by rezonings."

The current zoning regulation says that parking lots in the SP zone are not allowed to offer all-day commuter parking under the zoning commission's policy that lots in the SP zone meet the needs of people living in the area.

Blondell, however, said that a number of parking lot owners operating lots in the SP zone have been able to get variances from the Board of Zoning Adjustments that allow them to operate all-day commuter parking.

"The District government believes that continuing parking lots in the SP zone will help development, but the experience of the District of Columbia is just the opposite," said Hubbard, citing the existence of parking lots in SP zones in solid development areas such as those along Massachusetts Avenue. "It does not make it any easier for people to develop their land. There is no need for them, and they should be closed."