Confident they will succeed where several other developers have failed, officials of a Middleburg, Va., development firm said yesterday they have assembled a 3 1/2-block parcel of property in Arlington's Courtlands neighborhood and will pay the 30 property owners about $20 million.

The firm, Moyarta Corp. of Virginia, went to settlement yesterday with six owners of seven properties across from the new Arlington Court House Plaza development, said Ann Sheridan MacMahon, president of the firm.

They were paid about $4.9 million. The price was $60 a square foot. Individual property owners were paid from $390,000 to $996,000, MacMahon said.

The firm plans to seek county approval to build a housing development of 1,600 units in up to seven buildings, said Edward B. MacMahon Jr., a Moyarta director. He added the firm was negotiating to bring in a joint venture partner to help develop the site, which is near the Court House Metro station.

Moyarta will go to settlement in January with the 24 property owners who hold the remaining 27 parcels, Ann MacMahon said.

The largest chunk of the 10-acre site is roughly bounded by N. 14th, N. Barton and N. Wayne streets and Fairfax Drive. The second part of the site is across the street and is the north half of a block fronting on N. 14th Street between N. Wayne and N. Veitch streets.

The property owners who settled yesterday could not be reached for comment. John L. Melnick, a spokesman for 22 of the property owners who have yet to settle, confirmed that a deal has been made with Moyarta and that settlement is expected soon. The firm has put up a $600,000 deposit, he said.

Moyarta is a privately held firm run by members of the MacMahon family. If it is ultimately successful in this deal, it would partly end a four-year attempt by Courtlands area homeowners to make more money by selling their lots in one package.

Melnick's group of 22 neighbors thought it had a deal last year with the Zimpel/Silverstein firm of Falls Church. That deal collapsed as had two previous deals with two other developers.

Another group of 21 Courtlands property owners negotiated a deal last year with Alexandria developer Robert M. Stein and Associates. That deal fell through.

The properties assembled by Moyarta include all lots involved in the unsuccessful Zimpel/Silverstein deal and several of the lots that would have been part of the deal with Stein. It also includes two properties that had not been part of any previous consolidation.