A $3 million addition to the Fairfax County jail--including a special cell for the handicapped--is near completion, but even when it opens county officials said the five-year-old jail will remain overcrowded.

The jail has been inadequate since Feb. 11, 1978, the day it opened. County supervisors have been reluctant to appropriate funds for a larger facility, arguing that Virginia needs to consider alternatives to jailing criminals.

"Most people now realize all those programs are fine, but they don't work," said Sheriff M. Wayne Huggins, who long has pleaded for a larger jail. The county's rapid growth has contributed to making the 274-bed facility inadequate, he said.

The jail likely won't catch up with demand until 1985, Huggins said, when the county is scheduled to complete a second expansion, costing about $16.7 million and adding 270 beds. "That expansion is projected to carry us through the year 1995 to 2000," he said.

All the current 126-bed addition will do will mean fewer prisoners sleeping on mattresses on the floors, he said. "It is not meant to catch us up."

The jail, located in the county government complex in Fairfax City, will operate with about 20 to 40 prisoners over its authorized capacity after the renovations are completed in about six weeks, Huggins said.

Some sections of the jail are housing two to three times as many prisoners as they should, Huggins said. In the receiving area, where prisoners should not be held more than 24 hours, some are being housed for as long as three days because other cells are unavailable, he said. At times attorneys' visiting booths have to be used to hold the prisoners, he said.

The sheriff also said that day rooms, the areas in which prisoners are allowed to move about during the day, frequently are used as cells because of crowding.

Most of the jail's classroom spaces also have been converted into cells, forcing officials to cut out most education programs for lack of space. Many women prisoners are being housed in classrooms converted into cells, Huggins said.

"We will get some of that space back with the renovation," Huggins said. The number of women's beds will more than double from 12 to 25 and the beds for men will increase from 186 to 230, Huggins said.

Last fiscal year, the county paid $206,555 to other Virginia jails to house the county's excess prisoners, a cost Huggins said the county will only have to pay in rare circumstances.

Most of the cell additions were made in a vacant basement area that had first been considered for use as a county printing shop or a courthouse cafeteria. When it became evident the jail was too small, officials decided to use the area for expansion.

Part of the renovation, new facilities for trusties, opened last week. The remaining sections--the new receiving and classification cells, computer-controlled security center, 13 new isolation cells and two new padded cells--are expected to be completed in mid-October, Huggins said.

The renovation also includes designated holding areas for "drunks brought in to sober up," Huggins said, as well as the special cell for handicapped prisoners.

"We don't have many handicapped prisoners, but this will allow us to take care of them when we do," Huggins said. "When we don't have a handicapped prisoner, we'll use it for anyone."