Fairfax County Board Chairman John F. Herrity, who has said he was unaware of a potential conflict when he voted on a town house project proposed by a developer who was his real estate partner, issued a check for $10,157 to that developer for his one-quarter interest in a condominium venture.

Fairfax Commonwealth's Attorney Robert F. Horan Jr. confirmed that the check, a copy of which Herrity gave him last week, was made out to Hersand Builders Inc., the Fairfax development company that received a major zoning variance from the county board in February to build 137 town houses in the Springfield district.

"The check was payable to Hersand," said Horan, who is investigating whether Herrity violated state or county conflict-of-interest law, including a Fairfax law that requires supervisors to disclose publicly their financial relationships with developers appearing before the board.

Herrity entered into a real estate venture with Herbert L. Aman III, president of Hersand, and Aman's wife Sandra, who owns all the company's stock, two months before the zoning vote. Herrity owns a 25 percent share in a condominium office unit in Fairfax; the Amans have a 50 percent interest in the unit. Herrity has not revealed who controls the remaining share.

Herrity, in a letter he delivered to Horan on Thursday requesting a legal opinion, said Hersand's zoning application stated that neither the company nor its officials "had any business or financial relationship with any member" of the county board.

"Accordingly," Herrity said in his letter, "when the rezoning application came before the Board of Supervisors, I had no indication from the affidavits filed by Hersand that there would be any problem in my participating in the board's proceedings on the matter."

Herrity's argument is that Hersand's application did not include Herbert Aman's name, according to Richard E. Dixon, the Fairfax attorney whom Herrity has hired to represent him on the matter. Sandra Aman's name, however, was listed on the application as the 100 percent stockholder in Hersand.

"He didn't see Herb Aman's name on the application and so it didn't trigger in his mind that he may have had a problem," Dixon said.

Dixon said he was not aware that Herrity's check for his interest in the condominium was made payable to the Hersand company.

Contacted yesterday, Herrity declined to comment when asked about the check.

"The letter speaks for itself," said Herrity, who has refused all comment since contacting Horan. Herrity released the letter to reporters during the board meeting that night.

The Amans could not be reached for comment.

County law requires supervisors, before participating in a land use issue, to disclose publicly whether they have had a business or financial relationship, either directly or through a partnership, worth more than $50 with an applicant during the preceding five years.

Horan said he will decide by Thursday whether Herrity violated the law.

First elected to the county board in 1971, Herrity is serving his 10th year as chairman. In addition to his county position, Herrity runs a private insurance agency, Jack Herrity & Associates, which is in Fairfax City. This is the first time he has been the subject of a conflict-of-interest investigation.

Herrity's $10,157 check for his share in the real estate venture was dated Dec. 18, 1985. Hersand's application first came before the board one month earlier, on Nov. 18, when it was deferred for a week. It was postponed again on Nov. 25 and once again on Dec. 9. The board held a public hearing on the project on Jan. 27 and approved it, 6 to 2, on Feb. 10.

Herrity voted against the controversial rezoning application, which was heatedly opposed by civic groups and school representatives in Springfield, but then joined the other seven board members attending the meeting in granting Hersand's request for several waivers from county zoning regulations.

Dixon said Herrity's vote against the overall town house proposal eliminates whatever question there would be about a potential conflict. But Horan said the vote does not clear Herrity of possible prosecution.

"That doesn't make any difference one way or another," Horan said. "The statute doesn't say you have to disclose whether you vote for or against something. It just says you have to disclose."

A violation of the county's disclosure law is punishable by up to one year in jail or a $1,000 fine, or both, Horan said.

Herrity claimed a $10,315 loss from his investment in the property on his 1985 tax forms, which board members are required to file annually.

The office condominium is one of two investments he listed on his financial disclosure form, also on file with the county.