The Arlington County Board last night approved a proposed $100 million office-retail development in the Ballston section, which many hope will be the centerpiece for a new downtown.

The Ballston Galleria, to be developed on the site of the existing Parkington Shopping Center between Wilson Boulevard and Glebe Road, is designed to house 100 stores--including the existing Hecht Co. department store and another as yet unnamed "anchor," two 12-story office buildings and an eight-story garage to be built through a public-private financing scheme.

"This is the key that will unlock the potential in Ballston for a very delightful mixed-use community," said board member Ellen Bozman.

The financing of the 2,900-space parking garage proved the most controversial decision of last night's three-hour debate on the Ballston project. The board voted 4 to 1 to endorse the concept of a $25 million tax-exempt general revenue bond, to be issued by the county and used to finance improvement to the five-story parking garage now at the Parkington site.

Board member Dorothy Grotos cast the only vote against the critical financing package after complaining that the May Co., parent company of Hecht's and owner of the 13-acre Parkington site, had not lined up any agreements for the "anchor" store.

"I can't believe this board is willing to buy a pig in a poke," said Grotos, who also noted that the criteria set for the Ballston project were less demanding than those applied to other projects in Arlington.

But for most board members the critical issue last night was the development of the Ballston area, which surrounds a Metro subway stop, and the lure of attracting major retail outlets back into the county.

The Ballston area was developed in 1951 as one of the Washington area's first shopping malls. It had 19 stores. Over the years Arlington's shopping malls declined as larger malls were built farther out in the suburbs.

"This community and this board have expressed the desire that retailing be a major objective," said Board Chairman Stephen Detwiler last night. "Arlington missed something along the way and this may give us an opportunity to get it back."

Several citizens last night told the board that the garage financing package--without which the May Co. said it would not build the project--represented an unwarrented public subsidy of a private development.

"Don't be intimidated" by the May Co.'s threat to pull out of the project, said one citizen, John Magnusson, who asserted that parking spaces were not a legitimate "public improvement."

Francis McDermott, attorney for the May Co., said it would be prohibitively expensive for a private company to pay interest costs on loans for the reconstruction of the parking garage.

"I think I can safely and fairly say that you have a proposal that is very important to this community," said McDermott. "It is important from the standpoint of providing a new image to Ballston and it signals that Arlington is committed to very high-quality development."

Under the terms agreed to by the board last night, the county will pay for the cost of certain public improvements near the project, including roadway and water and sewer lines.

The total cost to the county is $1.6 million; the $25 million in bonds for the parking garage would be repaid through collection of parking fees.

In other business, the board made a concession to federal concerns over the Washington skyline and agreed on a new policy restricting building heights along the county's Metro corridor.

In a carefully worded resolution designed to end a feud with the National Capital Planning Commission, the board unanimously voted to "endeavor" to abide by the county's height limits on new buildings--180 feet for residential structures and 153 feet for office buildings--except in "clearly appropriate circumstances." Hitherto, the board has made occasional exceptions to its height limits in exchange for improvements, such as parks, paid for by developers.

The resolution was offered as a compromise between the NCPC's concern for a harmonious vista as seen from the monuments in downtown Washington and Arlington's goal of dense development along Metro's Orange Line.

"The board's action is an important step forward in preserving the historic visual character of the national capital," said T. Eugene Smith, NCPC vice chairman.

The board also voted last night to elect Margaret Ann Bocek to succeed Torill B. Floyd on the county's five-member school board.