Fairfax County schools will ask voters in a special referendum April 4 to approve $39.7 million in bonds to build seven new schools and renovate nine others.

The referendum will be the sixth the schools have held in the last five years. If the bonds are approved there will not be another school bond referendum for at least two years, school officials said.

The bonds would pay for seven new schools to be built in the rapidly developing western and southern portions of the county where schools are severly overcrowded.

"In the short term, there's nothing that could be removed from this referendum that wouldn't come back as needed in a very short time," said Toni Carney, co-chairman of the Citizens Committee for School Bonds, which is campaigning to get the bonds approved. "It makes sense to go with the bonds now and at least reduce the inflation problem."

If the bond issue passes, three elementary schools and one intermediate school would be built in the Reston, Herndon and Great Falls areas, the northwestern part of the county. The Pohick area, in the southern Springfield district, would be the site for two elementary schools and an intermediate school.

In addition, renovations would be made to a special education center, four elementary schools, two intermediate schools and two high schools in various parts of the county.

The Reston-Herndon elementary school, which would house 660 students and cost $3.2 million, would open during the 1980-81 school year. Mumford Park and Great Falls No. 2 elementary schools each would house 660 students and open in school year 1979-80. The estimated building cost for each is $2.9 million. South Lakes Intermediate School, which would serve the Reston-Herndon area, would open in school year 1981-82 and cost $7 million.

In the Pohick area, Rolling Valley West Elementary, with a capacity for 660 students, would be built for $2.9 million and Burke Center Elementary, would cost $3.8 million. Both would open in school year 1979-80. Chantilly Intermediate school also would be built for the Pohick area at a cost of $6.4 million.

Renovation work would be done at Centreville Elementary and Kent Gardens, both in the McLean area, and Woodley Hills in the Mount Vernon area. Renovations would total $2.5 million.

Renovation of Glasgow Intermediate in Mason District and Longfellow Intermediate in McLean would cost $2.7 million. Renovation at Fort Hunt High School in Mount Vernon and McLean High School would cost $4.6 million.

Also included in renovation plans is the conversion of an older elementary school in the northern part of the county into a center for the emotionally disturbed, which is expected to cost $295,000. The school has not been determined, but the center would be called the North County Center for the Emotionally Disturbed.

Specific renovations will vary from school to school but would include upgrading heating, ventilation, plumbing and electrical systems to meet county code requirements.In the elementary schools, renovations would include creating small gymnasiums and remodeling media centers and music rooms.

In the intermediate schools, renovation would include improving auditoriums, media centers, science labs and vocational centers. Air conditioning would be furnished in parts of the building used year-round by the community, including the administrative offices, media centers, auditoriums and cafeterias. All new schools would be air-conditioned.

The referendum will be held at regular voting precinct polls from 6 a.m. to 7 p.m. April 4. County residents must register to vote before March 21 to participate in the referendum. Residents may register to vote at the county general registar's office, 4031 University Drive, Fairfax City, 8 a.m. to 4:30 p.m. Monday through Friday.

Registration is also being held 7 to 9 p.m. Thursday nights at the county libraries that are normally open at night. All county libraries will be open for registration 7 to 9 p.m. today. The general registrar's office also will be open 9 a.m. to 5 p.m. March 25 and April 1 for those who wish to register to vote on Saturdays.

Absentee ballots may be submitted by some county residents already registered to vote. They include members of the armed forces, and those regularly employed outside the United States, as well as their dependents. Those attending school elsewhere and those physically unable to get to the polls also may file absentee ballots. The ballots must arrive at the general registrar's office no later than April 4.

County residents who know they will be absent April 4 may vote in person at the general registrar's office anytime before April 4.