The Rouse Co. -- developers of the new town of Columbia, the swank Shops at National Place and Manhattan's South Street Seaport -- said this week that it will open an 800,000-square-foot shopping mall July 30 in the Owings Mills Town Center as the first phase of an ambitious 15-year plan to develop 130 acres in the suburban area just northwest of Baltimore.

The developer said Saks Fifth Avenue, Bamberger's and the Hecht Co. will anchor the enclosed shopping center, which is expected to draw shoppers from Howard County and Baltimore, as well as the Towson and Hunt Valley areas.

The 130-acre parcel that Rouse controls in the 1,200-acre area called Owings Mills eventually will sprout 20 office buildings, with 2.3 million square feet of office space, two major hotels with a total of 700 rooms and accommodate an additional 400,000 square feet of mall shops and restaurants by the year 2000, company officials said.

Owings Mills, billed by Rouse officials as "something of a nephew" to the 1960s planned town of Columbia, is one of two areas targeted by Baltimore County as a hub for residential and retail growth.

In addition to the mall, and one 10-story, $14 million office tower now under construction at Owings Mills, the Columbia-based firm will open a 27-story, mixed-use office, hotel and retail tower at Baltimore's Inner Harbor in the fall of 1987.

The complex's blue-green reflective glass exterior will be physically connected to the original Harborplace shops, which Rouse also created, by a bridge over Pratt Street.

"Baltimore took off with the opening of Harborplace," said Rouse spokesman W. Scott Ditch. "Millions in development dollars have been poured into the downtown and now we want to cash in on the catalyst effect our initial investment has had on increasing property values and the desirability of the area."

The tower and hotel complex will encompass the entire city block bounded by Pratt, Lombard, Talbert and South streets, with offices commanding the best views and leasing for about $30 a square foot a year.

About 80 up-scale retail shops will occupy the first four floors above an 1,100-space underground parking garage. A seven-story, 600-room Stouffer Hotel will top the shopping floors with their open balconies and terraces. The top 15 floors of the complex will house 270,000 square feet of office space, which project developer Robert Minutoli said most likely will be leased to major financial institutions looking for a center city address within walking distance of Baltimore's Metro and rail stations and the business district.

The hotel, which will compete with the Hyatt Hotel already operating directly across the street, will surround an outside courtyard on the fifth floor and house Baltimore's largest ballroom.

These new developments at Owings Mills and Harborplace, with their emphasis on office space, are a departure for the Rouse Co., which has made its mark nationally by reshaping historic, yet down-in-the-heels urban centers such as Boston's Faneuil Hall marketplace or St. Louis' Union Station in showcase retail projects that leave the best of the old intact.

"It is a change for us," Minutoli said. "The Rouse Co. is doing office development on a scale not known before."

The company currently owns and manages some 37 million square feet of retail space nationally compared with about 2 million square feet of office space. These developments planned in the Baltimore corridor, coupled with similar multiple-use projects in Oregon, San Francisco, Louisville and New Jersey, soon will bring that office-retail ratio closer to 50-50, Ditch said.

"There's a synergism in mixed-use projects -- retail shouldn't be viewed as a stepchild," Ditch said. Minutoli said the mixed-use concept is not new. "It's been here ever since a guy started making pots and selling them outside his cave," Ditch said.

Despite these new projects in the Baltimore corridor and on the West Coast, Rouse said it will continue to maintain a strong base in Columbia, a 14,000-acre planned community that began as a drawing-board dream more than 20 years ago. It now is home to 66,000 residents in eight villages that are almost equidistant from the centers of Washington and Baltimore.

The 1,000-acre town center already includes the 200-store Columbia Mall and a dozen office buildings, of which Rouse owns 400,000 square feet. Rouse is now building a $13 million, 12-story Park View office building with 132,000 square feet.

Even with the completion of this building later this year and 1,200 apartments in downtown Columbia, Rouse officials said there is still enough available land there to build an additional 20 to 30 office buildings over the next two decades.

Will the Rouse Co. build so much, so fast, that it ends up competing with itself in a glutted office market?

Company officials say, "No." They noted that there are 95 percent occupancy rates at Columbia Mall and Harborplace and at their other Maryland office towers.

"We're not under any great pressure to develop Owings Mills. We will build what is conservative and safe to do in any given year," Ditch said.