Real estate developers now have an opportunity to submit proposals for a joint development with Metro of a major site above a key subway station at 4200 Connecticut Ave. NW.

The Washington Metropolitan Area Transit Authority, which owns the land on the west side of Connecticut opposite the Van Ness Center, is seeking proposals from developers interested in a long-term land and air rights lease for 65,600 square feet of land adjacent to the University of the District of Columbia and the planned International Center for foreign chanceries.

"No doubt about it, it's a good site," said Gerald J. Miller, who was the developer under a similar agreement for the development of the handsome, brick 1101 Connecticut building recently completed over the Metro station at the northeast corner of Connecticut and L NW.

But the sites are different. The developed site contains 17,500 square feet and is regarded as "prime downtown" worth about $400 a square foot (for land only) in today's escalating market. The uptown Van Ness site is nearly four times as large and zoned for far less "floor area ratio" per square foot, but still has 227,000 gross square feet compared with 175,000 on the downtown site.

With C-3-A zoning, the available uptown site has a height restriction of 75 feet on the north side and 35 feet on the south side. Lot occupancy cannot exceed 65 percent to insure adequate open space and pedestrian areas at street level. Bus bays and "kiss-ride" drop-off auto facilities must be provided.

Henry W. Cord, head of the WMATA real estate department, said that proposals are due March 15 for a planned unit development linked with the UDC campus on the former site of the National Bureau of Standards. The Metro space, with 400 feet along Connecticut (in front) was purchased several years ago by WMATA from Chevy Chase Land Co. for $2.8 million, or $42.50 a square foot. It now is likely worth nearly double that amount.

Before Metro took over, the site was occupied by Franklin Simon and Colony House stores. Across the street is the $100 million Van Ness Center development of 1,600 luxury rental apartments, several office buildings and a new highrise Consulate apartment. Realty professionals long have regarded that uptown location as the heart of one of the Northwest's most affluent areas.

Although Cord and Miller did not speculate on what might be built on the available site, the likely choice is an office building with some commercial space. Partial use as a hotel is possible, but the lease is likely to be too expensive for apartments.

Office space might be leased for as much as $12 a square foot for occupancy in 1981. Construction of parking and the lower part of the development is likely to be started in 1980 and is due for completion early in 1981 when Metro subway service is scheduled to be extended from the present terminus at Dupont Circle northward to Van Ness.

Van Ness is expected to be the northern terminal on the "red line" for about nine months until service is extended father north to the Grosvenor station at Pooks Hill in upper Bethesda, Cord said.

The "Van Ness opportunity" for private development with WMATA as the land - owning, land - leasing partner represents the kind of developments that have been done at Farragut North and Rosslyn and are being considered for Friendship Heights, McPherson Square, Silver Spring and New Carrollton. Intended benefits should be forthcoming for both the public and the private developer.

From the WMATA point of view, this kind of use provides long-term continuing income ($247,000 annually for the first 50 years for the first 50 years for the Farragut-1101 Connecticut site) plus a percentage of profit above an agreed-upon base for the private developer.

"It's something we can live with," said Miller about the 1101 building at Farragut North. He noted that the land-lease arrangement avoids the heavy front-end start-up cost of acquiring and owning the land but also works against favorable longterm financing because the land is not part of the mortgage. Miller said he is considering making a proposal for the Van Ness site.

Cord is optimistic that many developers will be interested. He said there were six competing bids against Miller for the Farragut site. Incidentally, Metro still has a site available (advertised last year) at 14th and I NW.

Although dollar terms of the lease agreement are likely to be less per square foot of space at Van Ness, the total may be larger than the amount negotiated for the downtown site. Terms will be stable for the first 50 years with renegotiation for the next 49. There also will be a return for WMATA based on total cash flow generated by the developer-owner of the building.

The detailed 32-page WMATA prospectus for the Van Ness site stipulates that the developer must provide a statement of qualifications and that Metro has the right to reject any or all proposals. However, Metro also has an obligation to provide station facilities by 1981.

Metro wants "development to the site's highest and best economic use and a variety of uses to the extent that economic feasibility permits." All taxes must be paid by the lessee-developer.

In addition, the prospectus notes that the final design of the project should be "complementary" to the UDC campus and that the building should be "sited and massed with due regard to the visibility to and from the campus."

Most of the site, which also has 175 feet of frontage on the south side of Idaho Avenue, is expected to be available to the chosen developer in early 1980.