D.C. Mayor Marion Barry said yesterday that the design for a new prison in the city will be completed before this fall's election, but he did not outline a construction timetable.

It was the first time the mayor, who has been accused by D.C. Council Chairman David A. Clarke and U.S. Attorney Joseph E. diGenova of delaying the construction until after his reelection bid, has set a time limit for any phase of the proposed facility.

Barry and diGenova appeared on CBS' "Face the Nation" (Channel 9) to discuss prison overcrowding, which has been cited as a contributing factor in last week's uprising at Lorton Reformatory.

City Administrator Thomas M. Downs said yesterday that a consultant who is studying the precise needs of the District is to submit a preliminary design for the new jail by the beginning of September.

"We would then start the next round of procurement, which would be a request for a design-build bid," Downs said. He said "design-build" is an "expedited process" in which the jail will be constructed at the same time it is being designed.

Barry, who blamed the nation's rising prison population on a "drug epidemic" that fuels crime, has said he wants the proposed prison to be a 700- to 800-bed drug treatment facility just southeast of the D.C. Jail and adjacent to Congressional Cemetery.

In an interview outside the CBS studio after the broadcast, Barry said that one way to reduce the population of the city's prisons would be not to lock up automatically persons who are in technical violation of their parole because of drug use. For example, he said, parolees whose urinalyses are positive as many as three times for PCP use should be warned against future use but should not be sent back to prison as long as they have a job.

Downs said that no such change has been proposed but that the idea is one Barry has been exploring.

"I think what he is saying is that if an individual is not in trouble and is employed and winds up with a single dirty urinalysis, it is unclear if the answer to that is an additional nine to 12 months in prison, and whether that should be automatic. It has to be taken in the context of a number of other indicators about what the individual is doing" while on parole, Downs said.

Barry said during his television appearance that in addition to building a new prison, he favors alternatives to incarceration for "people who commit nonviolent crimes and for some crimes against property," unless the offenders engage in a "constant pattern" of criminal conduct.

Barry said that the District government is seeking permission from the city's judges to allow inmates who serve weekend-only sentences in jail to work for the city instead, performing such jobs as repairing public housing; they would spend their nights at home instead of being incarcerated on Saturdays and Sundays. He said he hoped that the program could begin next month.

DiGenova said that building new prisons was "absolutely" the answer to the overcrowding problem. He said, however, that "not everyone who is convicted of committing a crime should go to prison," but he was not more specific.

After the program, Barry said the city will "prosecute the hell out of those identified" as having a role in starting fires in 14 dormitories at Lorton Reformatory's Occoquan I and II facilities on Thursday.

He said that a court-imposed inmate population ceiling at the D.C. Jail was "counterproductive" because it had led Occoquan inmates to believe that they would be released from prison if they burned down their housing units. Barry said the 1,375-cell jail, which has a cap of 1,964 inmates, could "comfortably" house 2,200 prisoners.