The Loudoun County Board of Supervisors denied a rezoning request on 57 acres near Dulles International Airport last week because the request lacked any provision for water and sewer service.

According to Supervisor Betty Tatum, who voted against the request, the developer, Dr. Patrick O'Leary, did not indicate at public hearings what the property, on Rte. 606, would be used for.

"I suppose he would put in water and sewers if he needs them," she said later. "My concern is that there may be uses on the books that don't need water and sewer service -- like an auto junkyard."

O'Leary had requested only that the land be rezoned from agricultural to general industrial use. He said he had a buyer for the property but that the sale was contingent on his getting the rezoning approval.

Meanwhile, a controversial agreement between the county and developers of a multifamily housing development was approved in a 5-to-3 vote last week. The agreement will allow Chase Heritage Associates, a Virginia limited partnership, to build a 236-unit housing project in Sterling with some federal tax-exempt funds because 20 percent of the units will be rented to tenants earning no more than 80 percent of the county's median household income.

The median household income in Loudoun is $31,000, according to a spokesman with the county attorney's office. Rents on the units have not been established, according to a spokesman for the developer.

In other business, the board:

* Heard from Budget Director Kirby Bowers that projected revenues for fiscal year 1985-86 total nearly $48 million, $5.5 million over last year's revenue. Part of the increase comes from a $1.7 million increase in revenue from real property taxes, a $1.6 million increase in personal property taxes and nearly $1 million in sales taxes.

* Authorized County Executive Philip Bolen and county attorney Edward Finnegan to investigate the possibility of taking an option on property in Leesburg on Rte. 7 for the purpose of building a youth shelter. The county currently rents a property in Sterling where from eight to 13 youths are housed. "The federal government will give us $150,000 toward the building if we have a specific site," Chairman Frank Raflo said.