Lorton Reformatory's Youth Center I, where 11 inmates were injured by shotgun blasts in a riot Monday, is one of the District's most trouble-prone prisons and frequently has been cited by prison experts as having some of the worst living conditions at Lorton.

The youth center, one of eight prisons at the Lorton complex, remained in a state of "lock-down" yesterday after about 350 inmates went on a rampage, setting 15 fires in the academic and administration buildings, four of which apparently were sparked by firebombs.

The two-hour melee, which began after a power outage shut off all the lights in the prison, ended when more than 125 riot-clad corrections officers fired two volleys of shotgun blasts and 98 tear gas canisters at the inmates.

Walter Ridley, associate director of the D.C. Department of Corrections, said yesterday that four inmates who are suspects in the beating of a guard during the uprising have been placed in segregation. He said an estimate of damage caused by the fires was not available.

Fairfax County Board of Supervisors Chairman John F. Herrity, who has long sought to have the District-run prison removed from the county, yesterday sent letters to Mayor Marion Barry, Attorney General Edwin Meese III, U.S. District Court Judge June L. Green and the Northern Virginia congressional delegation, urging them to consider the citizens of the county when making decisions that affect Lorton.

"By any measure [Monday's] incident qualifies as a major explosion of the powder keg that is Lorton," Herrity said. "Surely, as the season gets hotter and the Lorton facilities become more and more crowded, the potential for hazards to the public safety grows."

The youth center, which opened in 1958 and has a capacity of 406 inmates, is one of the four facilities run by the D.C. Department of Corrections that have court-ordered population ceilings. The others are the D.C. Jail and Lorton's Maximum and Central facilities.

According to a 1984 study of Lorton Reformatory that was commissioned by Fairfax County, from April 1983 to March 1984 at Youth Center I there were 34 fights between inmates, 16 inmate attacks on guards and an average of 92 disciplinary reports a month -- higher than any Lorton facility except Maximum.

In December 1983, 13 corrections officers were injured when 200 inmates at the prison went on a rampage that was sparked by unfounded rumors that a female visitor had been strip-searched.

Located next to a 300-acre landfill, the prison was the site of two methane gas explosions in December 1984 that critically burned two inmates and forced the evacuation of prisoners for eight months while work crews installed underground barriers to prevent gas from leaking into the 53-acre prison compound. After 190 of the inmates were transferred to Youth Center 2, severe overcrowding at that facility sparked a massive fight between inmates of the two prisons that was quelled with tear gas.

A recent study of the D.C. Department of Corrections by criminologist Sean McConville of the University of Illinois recommended closing Youth Center I because of its "appalling location."

"Besides the smell, there is a constant and revolting swarm of flies," the report stated. "The physical discomforts of the site apart, the inmates are well aware of the symbolic significance of their being located amidst the garbage."

Ed Koren, a staff attorney for the American Civil Liberties Union's National Prisons Project said Monday's uprising "was not unusual and totally inevitable. It was just D.C.'s turn and it's going to continue to happen because they are not getting at the underlying problems . . . . They just move from crisis to crisis."