The problem of crowding at the Prince William-Manassas Regional Adult Detention Center in Manassas remains significant, and county officials may have to add modular housing units as a temporary solution, according to center Superintendent Richard Kiekbusch.

In early 1987, the number of inmates at the 175-bed facility rose as high as 299; as many as 80 of them were awaiting assignment to state prisons after felony convictions. The crowding prompted county and city officials to threaten to sue the state.

Now, the number of so-called state prisoners has fallen to 59, but the total number of inmates has continued to increase. In July through September, the number of inmates averaged 269, with the high at 312.

Inmates are routinely doubled up in cells meant for one, creating tension and morale problems, Kiekbusch said.

"You're asking for trouble when you operate like this," he said.

A $7.2 million, 125-bed expansion could be completed by late 1990 or early 1991, jail officials estimate.

But the prison facility, which still must receive funding approval, is in competition with other needed projects, including roads, schools and the possible expansion of the county courthouse.

The Board of County Supervisors has authorized the county staff to work with jail officials in developing a proposal for the design of the jail expansion and has appropriated about $40,000 for a needs analysis study.

In addition to purchasing modular temporary housing units, officials are considering renovating other buildings for prison use.