D.C. Mayor Walter E. Washington yesterday rejected hardware executive John W. Hechinger's proposal to build a privately financed convention center on a site owned by Hechinger's firm in northeast Washington.

The mayor said he accepted a recommendation from Ben W. Gilbert, director of municipal planning, that the city stick by its original plan for a $110-million convention facility downtown, near Mount Vernon Square NW.

The Hechinger site at the intersection of Benning Road, Maryland Avenue and 17th Street NE "is not a good site for the civic (convention) center," Gilbert told the mayor in a report. "The civic center should not be located (there.)"

Hechinger proposed on Oct. 24 to build the center on 8.5 acres now occupied by his firm's lumber yard, warehouse and corporate headquarters. He said he would lease his center to the city for $1.5 million to $2.5 million a year below the cost of the downtown facility.

The city's proposal has encountered strong and possibly fatal opposition in the Senate, which rejected a city request for an appropiration of $27 million to complete plans and acquire the three-block site south of Mount Vernon Square in the city's old downtown.

A Senate-House conference committee seeking to settle the issue has broken off its sessions without a final decision. The House has approved the city's $27 million request.

An aide to Sen. Patrick J. Leahy (D-Vt.), chairman of the Senate District Appropriations Subcommittee, said the senator still believes the city's proposal should be dropped from the pending budget bill and that alternatives should be explored during the next few months.

Gilbert, in his report to the mayor, said the Hechinger site was considered and rejected when the downtown location was being selected.

While the Hechinger site has some plusses, including land already assembled under one ownership, Gilbert said "those (advantages) are considerably outweighed by problems, in to downtown, higher risk of achieving spin-off benefits (through adjacent private development), and impacts on the surrounding neighborhood."

Hechinger said yesterday that he anticipated the city administration's rejection of his proposal, and intends to challenge it, perhaps by some legal process.

To many Washingtonians "are so northwest chauvinist that they don't realize there are other vital parts of the city," Hechinger declared. "People who come here (for conventions) from other cities don't really care if the center is in northeast as long as it is accessible and has all the amenities."

Gilbert, in his report, said the Hechinger site is more than two miles farther from existing downtown hotels than the Mount Vernon Square site, and is not directly accessible by Metro subway.

"Our studies have stressed the need for a well located center to insure optimum use, and the related delegate spending and (adjacent) spin-off development," Gilbert said.

"With the locational problems of the Hechinger site, use and spin-off development could well be less than with a well located center. Thus, though initial cost would be less because of no land (investment by the city), the overall risk would be greater."

Gilbert contended that the size, triangular shape and topography of the Hechinger site, which is partly sloping, would dictate a less suitable design than the flat, downtown location.

Gilbert said the Mount Vernon Square site is close to major restaurants and department stores, while those near the Hechinger site are neighborhood-oriented and not likely to attract the level of spending by conventioneers that would contribute heavily to city sales tax revenues.

Hechinger disagreed, saying downtown is showing signs of a revival without the convention center and that such facilities as hotels and restaurants would sprout in the northeast in response to the center's construction.