All that Jordan Tannenbaum wants to do is restore quiet to the tree-shaded streets of his Colonial Terrace neighborhood, a collection of small frame houses lining a semicircular drive near the Potomac River in Rosslyn.

To do that, he is fighting plans for an 18-story condominium that would bring the clammer of jackhammers to his small neighborhood, just a few blocks from the dust and din of the final stages of I-66.

Tannenbaum claims his landlord has threatened to evict him from his apartment for opposing the condominium proposal. But Tannenbaum has not wavered, and is battling the planned high-rise with gumption and the help of his neighbors.

This week, despite a series of protests designed to garner support from community leaders and politicians, Tannenbaum lost round one when the Arlington County Planning Commission approved the condo proposal by a 6-to-5 vote.

But Tannenbaum said after the commission meeting Monday night he was "encouraged by the close vote." He added, "We don't view it as a defeat at all."

Under the proposal presented to the county, Knightsbridge Development Company of McLean plans to construct a salmon-colored, luxury condominium project at North Key Boulevard and 18th Street North, just north of the Iwo Jima Memorial and Arlington Cemetery.

The $50-million project, named North Key Plaza, would include 357 condominiums, with such touches as two-story units and greenhouses.The units, developers say, would cost $150,000 to $200,000 each. Knightsbridge, according to disclosure statements filed with the Arlington zoning office, is controlled by seven Kuwaiti investors.

The proposal, said Arlington County planner Rob Baker, is part of the largest construction boom in Arlington since the real estate market capsized in 1973. "This is the heaviest crunch of new development we've ever seen," he said.

In the Rosslyn corridor alone, the Arlington County Planning Commission is considering plans for more than 1,000 residential units, primarily condos and townhouses, that would give the area its first infusion of concentrated housing construction in nearly 20 years, in contrast to a 10-year trend toward hotels and office buildings. By the year 2000, county planners have estimated, there could be a residential shortfall of nearly 3,000 units in the Rosslyn area, and they believe the trend toward more residential construction could avert that problem.

That trend was evident in planning commission actions Monday. In addition to backing the Knightsbridge plan, the planning commission endorsed a project to build a 503-unit high-rise condominium next to the Zerox building in the 1400 block of North Fairfax Drive.

The commission also approved plans to build several smaller condo, townhouse or apartment developments in the Rosslyn area.

The commission's decision on the Knightsbridge proposal apparently was swayed in part by arguments from Marc E. Bettius, an attorney representing Knightsbridge, who contended that Arlington Should welcome developers who want to build living quarters to balance Rosslyn's strictly business image.

Several commission members, including Chairman Tom Malesardi, were obviously impressed by an unusual offer from the Kuwaiti owners of Knightsbridge to donate three existing apartments buildings, also on North Key Boulevard, to the non-profit Arlington Housing Commission for low- to moderate-income housing.

The total value of the three buildngs, according to Bettius, is $1.1 million, and he made the offer on behalf of his clients in exchange for commission approval of a change in the county master plan. The requested change, which was approved, would allow Knightsbridge to increase the height of its project from the current limit of 12 stories to 18 stories.

Despite the endorsement from the planning commission, the North Key Plaza project still faced the scrutiny of the five-member County Board. The Board is expected to make a final decision on the planning commission recommendation at a meeting Saturday.

At least one board member, Dorothy Grotos, predicts tough going for the plan.

Grotos said she is skeptical of arguments to alter the master plan, and added that she is unimpressed with the $1.1-million housing offer.

"We often hear about these great deals," said Grotos. "But when it comes time for the action, nothing happens. We'll have to be very careful."