Work crews have begun construction on a $47 million, 516-bed jail that will replace Arlington County's crowded corrections facility with one that officials say will provide better security and lower tension among inmates.

The new jail, at North 15th Street and Court House Road, is scheduled to be completed in the summer of 1992, Chief Deputy Sheriff Tom Faust said. It will include "shell" space that could be used to add another 144 beds, he said.

Workers also have begun excavation work for a proposed courthouse that would be next to the jail, even though the $53.8 million bond package that would finance that project will not go before voters until Nov. 6.

The excavation work is included in the jail's construction because an underground parking facility will be built there even if the courthouse proposal -- which has wide support among Arlington officials, civic leaders and neighborhood groups -- is rejected by voters, Faust said.

Although the master plan for the courthouse area calls for the old jail to be torn down once the new one is opened, Arlington officials haven't said whether they will destroy the older facility, which was designed for 164 inmates but has held up to 400.

Several groups of residents have urged the county to save the old building and use it for a jail release facility Arlington officials have said is needed, but officials privately say they doubt the older facility will be preserved.

Faust said the new jail will be divided into several units, each of which will hold about 40 inmates and have a day room and separate access to recreation areas. He said each unit will have "direct supervision" of inmates, meaning that at least one corrections officer will be inside the unit with the inmates at all times.

By giving inmates more space and supervision, Faust said, officials should be able to ease the increased tension among inmates that has plagued the current jail.

"We will have a deputy literally in the middle of the housing area," said Faust, who said jails in Prince George's County and Alexandria use a similar system. "It should help us head off a lot of problems."