Neiman-Marcus chairman Richard Marcus braved airport hordes at the start of the holiday weekend yesterday, for a one-day trip to Washington.

His aim was to deflate persistent trade rumors that the Dallas-based retailer is unhappy with its 100,000-square-foot store in the District, located at Mazza Gallerie, a mall troubled initially by construction delays and now by subway construction outside and empty store space inside.

In an early-morning interview before meetings with local Neiman-Marcus employes and executives in charge of the mall, Marcus could not have been more emphatic about the company's plans here.

Not only have sales here to date exceeded projections, but the firm will add a restaurant and beauty salon to the Northwest Washington store in an expansion over the next year.

A second Neiman-Marcus store is still on the drawing boards, with several potential sites, under consideration - the most likely one in Northern Virginia. But Marcus doesn't want any other location for his first store here, which is located atop a future subway entrance between affluent D.C. and Montgomery County.

Moreover, with a new company in charge of leasing, Marcus and store manager Anthony Harriman predicted yesterday a much more "aggressive" drive to fill up Mazza Gallerie, which is now about 80 percent leased.

Within a few months, they revealed, McDonald's will open a fast-food unit on the ground floor. But to reflect the relatively affluent orientation of most Mazza Gallerie stores, this hamburger stand will be different. It will be similar to a "sophisticated" restaurant run by McDonald's at Water Tower Place, a high-fashion retail complex in Chicago.

Discussing the local Neiman-Marcus store, opened several years behind schedule but just in time for the 1977 Christmas season, Marcus said the sales gains here in April were "as high or higher than any store we have."

He conceded that small space allocations for some merchandise selections were wrong at first. Some sections were too large and others too small. Women's sportswear, for example, was expanded recently in view of customer demand, and business in recent months "has been sensational."

Asked about complaints that the local store lacked depth and variety to those customers familiar with Neiman-Marcus in Dallas, the chairman noted that a store with twice as much space obviously can offer more goods and that "we must edit for smaller stores."

Marcus said the Washington store "developed remarkably quickly for a new store . . . To be in this business you must have patience . . . with more expensive goods, the customers have an existing relationship with other stores and we have to woo them . . . it takes time but we've been more successful here than any store we've opened."

Neiman-Marcus, which will have a dozen stores when a third unit in Dallas opens later this year, originally forecast that the Washington store's sales would be $100 a square foot, or $10 million a year.

Marcus said annual volume has exceeded that level and that sales here "exceed several other stores as large if not larger. We have no pessimism at all about doing business here," he said. I wouldn't trade this location for any other in the D.C. area."

Marcus said reports about company dissatisfaction with its Washington location "are completely untrue . . . We didn't come here to test the market for five years, but to be here for a long, long, time," Marcus emphasized.

Nationwide, Neiman-Marcus plans to concentrate future expansion on the California market and cities, such as Washington, where there is now one store but where two would offer certain economies.

Neiman has stores in Beverly Hills and Newport Beach and is working on plans to enter the San Francisco market.

Marcus noted that sales of the company, a division of Carter Hawley Hale Stores, "have been strong all spring . . . but consumer debt is high. At what point does that offset a willingness to buy?"

Carter Hawley Hales sales rose 30 percent in the first quarter to $487 million, while earnings to $6.1 million (21 cents a share) from $5.5 million (19 cents).

Coldwell Banker, a national real estate company, recently was hired to replace the area firm of Shannon & Luchs as leasing agent for the D.C. mall, developed by Exxon Corp. and local investors. CAPTION: Picture, Neiman-Marcus Chairman Richard Marcus at Mazza Gallerie entrance to store's third level yesterday. AP