A classic battle between pro- and antidevelopment forces is about to be launched as the District Zoning Commission prepares to hear arguments over the the fate of the Tregaron estate, the last major piece of privately owned, undeveloped land in Northwest Washington.

At a preliminary skirmish recently, about 70 Cleveland Park residents turned out for a zoning meeting to argue the issue with the tract's developers.

Opponents of the plan to build 120 single-family homes on the historic estate just west of Connecticut Avenue will have another opportunity to speak out against it Monday.

"We think it development of the estate can be done with sensitivity to the site and the historic nature of the surrounding neighborhood -- and with much less impact on traffic," said Jacques B. DePuy, attorney for Friends of Tregaron. "We say you've got to go back to the drawing board. This plan is so fundamentally deficient, it ought to be rejected."

The Tregaron Corp. has asked the District Zoning Commission for preliminary approval to build the homes on a 14.6-acre portion of the old estate.

Several community groups oppose the plan because of the site's historic nature and the impact they contend the development would have on their neighborhood.

The zoning commission has kicked off a series of hearings on the Tregaron Corp.'s applications for a zoning change to allow higher density construction at the site and for preliminary approval of a planned unit development (PUD) designation, a category of development for which the commission can set special requirements independent of normal zoning restrictions.

The Tregaron Corp. argues that the development would be a positive addition to the community and would meet all city planning concerns, including preservation of the historic character of the site and compatability with the surrounding neighborhoods.

The project is controversial for the same reason that it would almost certainly be profitable -- its location. The 21-acre expanse of forested hills is bounded by Klingle Road, Macomb Street and the Twin Oaks estate. The irregularly shaped site was carved out of the estate of former U.S. ambassador to the Soviet Union Joseph E. Davies, who died in 1958.

When Davies' heirs could not agree on disposition of the estate in 1980, a D.C. Superior Court judge ordered the family's 1912 neo-Georgian mansion and the surrounding 6.4 acres sold to the Washington International School.

The other 14.6-acre section was sold to the Tregaron Corp. Other developers had eyed the site but dropped plans for building there, leaving it as a kind of unofficial addition to Rock Creek Park.

The Tregaron Corp. is basing its case for the development on the contention that the carefully planned construction of clustered homes under a PUD designation is the best way to preserve an estate that has not been and could not be maintained in its original state.

Under the site's current R-1-A zoning, the Tregaron Corp. estimates it could build 80 detached single-family homes on lots at least the required 7,500 square feet.

Under the R-1-B zoning designation, the developer estimates 130 units could be built on lots of at least 5,000 square feet.

"In order to build the allowable single-family housing under R-1-A and R-1-B zoning, it would necessitate almost a total destruction of the site," Tregaron architect Robert L. Ziegelman told the zoning commission.

Instead of building detached houses, Ziegelman proposes construction of clusters of homes to "preserve and protect the present topography and vegetation of our beautiful site and to keep a large portion of it unbuilt upon."

According to the architect, only 30 percent of the site will be taken up by the 120 homes, parking spaces, roads and driveways. About 10 acres would be left undeveloped, and 92 percent of the trees on the site would be preserved.

The plan also calls for preservation of such historic features as the original road leading to the mansion, stone retaining walls around the house and bridges.

As Ziegelman pointed out, the density of the development is a key issue. Because planned unit developments are not subject to the standard zoning regulations governing lot size, the Tregaron Corp. would not be subject to the maximum density limit of the current zoning if its PUD application is granted.

The higher density zoning would be consistent with the surrounding neighborhood, most of which is zoned R-1-B, Ziegelman said.

If the commission accepts the plan, with or without modifications, it will invite the developer to submit a more detailed PUD proposal for final approval.

The key planning agencies that must review the project have called for several modifications to the plan.

The most positive assessment came from the District's Office of Planning and Development, which recommended approval of the plan in a report issued in September.

The report endorses the developer's efforts to preserve undeveloped space and the historic characteristics of the site. It supports the developer's contention that the proposed density of the project, roughly 8.2 units per acre, "is not out of keeping with the area and specific location." The report says the project would not overburden neighborhood streets, although more parking spaces should be added.

The report, however, recommends modifications, including removal or repositioning of several clusters of homes that impair the views to and from the mansion or conflict with land uses planned by the Washington International School.

The National Capital Planning Commission was more critical in its Sept. 21 report, which proposed a substantial reduction in the density of the development "to avoid overwhelming the landmark qualities of Tregaron" and elimination of the houses that would be visible from Klingle Road.

The Joint Committee on Landmarks, which contributed to the Planning Commission report, has already recommended rejection of the original plan as well as a revised version. Because the site has landmark status, the panel will get another crack at the project if the PUD application is approved. The committee would then review the plans and recommend whether the city should grant a building permit for the project.

The most determined opponents of the project will come forward Nov. 1 to argue for outright rejection of the PUD application.

"The opposition is premised upon the fact that the density in the immediate neighborhood is much more akin to the density of R-1-A than R-1-B," said DePuy. "Any new development should be compatible for what's there now."

Friends of Tregaron will also contest the application on historic preservation and environmental grounds, arguing that the developer's plan is not appropriate for such a location, DePuy said.

Finally, the organization will present alternative plans for development of the site. "My clients assume development will occur. It's a question of how," DePuy said.