Not long after the turn of the century, with the emergence of a new philosophy that men who did bad things could be rehabilitated, a place called the Lorton Reformatory was constructed. Situated on the sprawling countryside of what was then, as now, essentially a rural area, its inmates from the city were supposed to benefit from the open space and fresh air and learn how to grow and sell vegetables and raise farm animals.

In those days, most inmates were white and, while the institution had its share of serious offenders such as murderers and rapists, prison records show that many were serving time for disorderly conduct and a variety of alcohol-related offenses.

Lorton today is a vastly different place. Its population is nearly 100 percent black. It is as congested and overcrowded as any city housing project, and it has become a warehouse; rehabilitation philosphy seems passe. Now the move is to build a new prison.

Last month, the Correctional Facility Study Commission recommended that no new D.C. prison be built, but Mayor Marion Barry rejected its findings and put the matter of what to do about the city's criminals in the hands of the U.S. Department of Justice.

The way things are going, there will be a new prison in the city sooner or later. But the reasons why the study commission argued against this bear closer study before a major mistake is made.

Consider the facts: The District has the highest rate of incarceration in the nation: more than 1,300 prisoners per 100,000 residents. The D.C. Jail and Lorton prison currently are filled to capacity with approximately 5,924 inmates. Thus, if the city opened a new 500-bed prison, it would be filled immediately.

In fact, if the city opened a 1,000-bed prison, it would be filled within a week and, if the city opened a 2,000-bed prison, D.C. inmates in federal facilities might be sent back here and that prison, too, would be filled.

The bottom line is that the inmates still will be warehoused and, when and if they are released, they will return to the streets in worse shape than when they went in.

Nearly 30 percent of the men in prison are there because of drug charges, which often stem from police sweeps through newly gentrified areas of the city. One way to relieve overcrowding is to stop sending men to prison who need other kinds of help.

Jerome Miller, director of the National Center on Institutions and Alternatives, testified before the study commission that approixmately 50 to 60 percent of the District's prison population could be put into alternative programs if the cost of their confinement could be spent on those programs.

The commission suggested that a possible alternative to incarceration would be diverting offenders out of jails and into alternative programs that surely would cost less than the $15,000-plus now required to keep each inmate for a year.

If half of the city's drug and prostitution cases and two-thirds of its property cases could be diverted, it is estimated that the detention rate could be reduced by 25 percent. Divert the Hispanic community's deportation cases and the reduction would be greater.

The commission made its most important recommendation when it called for an intensive probation program for convicted offenders. The kinds of programs it had in mind have been proved to be effective in many states around the country, including Virginia.

Before ground is broken for a new prison, a complete and reliable classification of all inmates is needed, the commission said, in order to determine who could benefit from something other than doing time in a warehouse.

This would be a good first step toward coming to grips with the complex issue of crime control in this city.