A Prince William County real estate firm, two-thirds owned by a county supervisor and a state delegate, last summer helped broker the sale of a 16-acre property, negotiated for a 50-acre parcel and asked dozens of owners if they would sell their land near a site that county supervisors were privately considering for a new administration complex.

Supervisor G. Richard Pfitzner was participating in the board's closed discussions on where to build the complex while his partners, Del. David G. Brickley and a real estate broker, were pursuing the business deals near Dale City. In one closed session in July, Pfitzner made a motion, approved by the board, directing the county search for the first time to include the general neighborhood where his firm was active.

The supervisors officially chose a site in that neighborhood last week, and their decision is likely to increase land values in the area. The 16-acre tract that the firm brokered for investor J.V. Elrod is now on the market for $89,600, almost 50 percent more than the $60,000 purchase price. The company, B.H.P. Real Estate and Investment Corp., would earn a commission of between 6 and 10 percent on a sale, Elrod said.

Virginia law allows county boards to meet in private to discuss land purchases. State law, however, forbids officials from improperly sharing or profiting from confidential government information.

Pfitzner, chairman of the county Democratic party, and Brickley, a Democrat who has led the county legislative ticket in every election since 1975, said in separate interviews last week that they did nothing improper. They both said their firm's activity simply reflected sound business judgment. They both already owned land near the 142-acre county site--known as the Davis tract--and Brickley said he has looked for more property in the vicinity for several years.

"If a man can't invest in his own county, where can he invest?" Brickley said during a telephone interview from Richmond. "I've never spoken to a board member, I've never spoken to a planning commission member, I've never spoken to the staff about where the county complex was going to be. I would have refrained from that whether Rick Pfitzner was an associate of mine or not."

Pfitzner, whose law office handled the settlement on the 16-acre tract, said he played no other part in the dealings on that property or the search for more land in the area. He said Brickley and broker Virginia Hoy, the third partner in B.H.P., handled the business deals. He agreed with Brickley that they never discussed where the county would place its complex.

In addition to the 16-acre tract, B.H.P. negotiated a $250,000 contract that later collapsed for an investor to buy a 50-acre parcel immediately adjacent to the Davis tract. The real estate agent who negotiated for the landowner said last week she believes the land is now worth more than $300,000 because of the board's decision.

B.H.P. also sent more than 50 letters asking property owners whether they wanted to sell their land along a three-mile stretch of road on both sides of the Davis land, Hoy said in an interview last week. Hoy signed the letters, which were written on B.H.P. stationery.

Pfitzner owns two homes and 12.5 acres of land, valued together at $130,400 by county tax assessors, across a dirt lane from the Davis tract. He and Brickley and a third partner--former Del. Erwin S. (Shad) Solomon of Bath County--own 8.5 partially developed acres a half-mile away that are valued at $126,800. Those properties were acquired before Pfitzner was elected supervisor in 1978.

Pfitzner abstained last week from the final 4 to 2 vote in favor of the Davis tract. He said later he was following the advice of an editorial in the Potomac News, a Woodbridge newspaper, that reported in January that Pfitzner owned land near the Davis tract, by then rumored to be the supervisors' choice for the new government center.

Pfitzner said he actively participated in the board's closed sessions. The Davis property was not included in the county's search area until Pfitzner made a motion, accepted by the board in a July meeting, to widen the search further to the east. Pfitzner, who represents an eastern district, said he made the motion to bring the government complex closer to eastern Prince William's population centers.

Eastern Prince William, with its fast-growing suburbs along Interstate 95, has tried for years to grab the courthouse or administration center away from Manassas, the county seat in the more rural west. The county board, where eastern supervisors now hold a 5 to 2 majority, took its first official step toward moving the administration center last spring, when it set aside $1.75 million as the first installment of the needed funds.

Pfitzner joined with the majority in that public 4 to 3 vote. The board then began meeting privately to discuss where the center should go.

The county park authority was at the same time negotiating to purchase the Davis tract for ball fields and other recreation. On July 21, the county board publicly authorized park officials to buy the land for $500,000, with Pfitzner joining the 5 to 2 majority at the open meeting.

By August the supervisors were privately discussing the Davis land as a site for the county complex, according to John R. Proctor, a Prince William finance officer who led the search. They told park officials of their interest in the Davis site in October, Proctor said, and by November that site was the leading contender for the county complex.

The board then waited until the park authority completed its negotiations with the Davis family and settled the purchase on Jan. 8. Last week the board voted 4 to 2 with one abstention to begin planning the development of the site in cooperation with park officials, who will still use some of the land for recreation.

B.H.P. had been incorporated in October 1980 to act as the real estate arm of Brickley's Dominion Mortgate and Investment Corp. but did little business during its first year, Hoy said. Brickley's mortgage company, Pfitzner's law firm and B.H.P. are all located in office condominiums that Pfitzner and Brickley developed four years ago on Davis Ford Road, a half-mile from the county site.

In early August, B.H.P. offered $250,000 on behalf of an investor for a 50-acre tract adjoining the Davis land, according to Mary Glass, the real estate agent who represented the owner. Glass said that in light of the county's later decision she is pleased the sale, which collapsed in October because of illness in the owner's family, did not go through.

"If I'd known (of the decision), I would have surely told people not to sell," Glass said, adding that the 50-acre tract probably increased in value by $60,000 or $70,000.

B.H.P. successfully completed a second sale that was also arranged in August. J.V. Elrod, an 82-year-old Arlington investor with large holdings in Prince William, bought the nearby 16-acre tract for $60,000 and put it on the market soon thereafter, with B.H.P. acting as broker. Elrod said in an interview last week he did not know where the county complex would go, but believed Hoadly Road is a good place to invest. He said he does not recall how he learned that the tract was for sale last summer, but said he first considered buying land in the area more than two years ago.

"If the county goes ahead and builds its administration buildings, well, naturally, it will enhance the value of the land," Elrod said in an interview. "But I'll probably be gone before it happens, the slow way they move."

Elrod said that he placed the land on the market shortly after buying it because he would like a quick return. If he finds no buyers at a reasonable price, he said, he will hold onto the property.

D.J. Martin Jr., a car dealer who with two relatives owned the 16-acre tract, said he put it up for sale last summer because the car business was slow and he needed the funds. He said that he did not know the county government might move to the Davis site, but that he does not regret selling the land when he did.

Pfitzner first said in an interview that he was not involved in either deal near the Davis tract. In a second interview last week, he said that the deed for the 16-acre property was prepared in his law office for the November settlement and that he and a Manassas lawyer acted as trustees for the mortgage. The supervisor said that, as one of the few lawyers in the area, he routinely prepares deeds for real estate sales in the neighborhood.

On Sept. 14, B.H.P. sent more than 50 letters to neighboring landholders saying an unnamed client had expressed interest in buying their land. Virginia Hoy, the broker who signed the letters, said B.H.P. was not looking on behalf of any particular client, but was trying to build an inventory of properties to sell to clients generally.

Brickley said he has wanted for several years to invest for himself in that area and has put feelers out before--including one attempt to buy the Davis land itself--but none has been successful since the shared purchase of the 8.5 acres four years ago. Davis Ford Road is a natural growth area because it provides the main route between Manassas and Woodbridge, he said.

"I've been convinced for a long time that eastern Prince William is one of the best kept secrets in the Washington metropolitan area as far as land values go," Brickley said. "I'm just completely sold on Prince William County."

Brickley said his firm had no more knowledge about the county site selection than anyone else, although one of its partners was at the time helping pick the location. "In looking at a map and trying to figure out where it would be, the most likely would be in the Davis Ford area," Brickley said.

As it turned out, B.H.P. could interest no other property owners in selling. Pfitzner said he did not know about the letters.