Halfway through construction on the first new correctional facility to be built in the District in nearly two decades, some neighborhood activists who fought to block the facility have become enthusiastic supporters..

The sprawling structure now taking shape behind the D.C. jail at 19th and E streets SE represents not only 800 new beds for the District's badly crowded corrections system, but also a new approach to caring for inmates with alcohol and drug abuse problems.

The new $50 million Correctional Treatment Facility also will offer a new program to teach inmates how to live successfully outside of prison and break the cycle of recidivism that plagues many of them.

The new facility, financed by the federal government, was proposed in 1986. But it took more than three years of political wrangling and legal battles before construction began a year ago.

A series of five interconnected buildings, the new 450,000-square-foot facility looks more like nearby D.C. General Hospital than the city jail in front of it. And in many ways, it will carry out hospital-like functions that for the most part have been lacking in District prisons.

About one-third of the inmates, 256, will receive treatment for drug and alcohol abuse. The facility's mental health unit will house 256 others. The third major component of the facility will be a reception and diagnostic unit where inmates just entering the city's prison system after sentencing will be evaluated and classified.

On a recent tour of the construction site, Edith Fitzhugh, project manager for the D.C. Department of Public Works, and James Baldwin, senior project manager for one of the two private firms that have been contracted to build the jail, credited the unusually mild weather in January and February for the fast pace of construction.

The structure now is a combination of open girders and a few permanent walls. Baldwin said that by "the end of September or early October, it will all be enclosed."

Fitzhugh and Baldwin said the structure should be completed on time, in November 1991, and turned over to the Department of Corrections for a phased-in opening that should have the entire facility operating by the following March.

Throughout construction, neighborhood residents and community activists on a special advisory panel have assisted in the detailed planning.

Because of their concerns, for example, a special driveway for construction traffic was built from an access road to RFK Stadium to keep heavy equipment off surrounding streets.

Similarly, the city agreed to erect a tree-lined, raised earthen berm to separate the facility from adjacent Congressional Cemetery, after citizens complained that the historical area could otherwise seem dominated by the massive jail structure.

And because of community objections to the hulking institutional look of a light colored building , the concrete walls of the new facility will be a dark rose that is more the shade of old red brick.

Corrections officials also have worked to involve those who fought most fervently to keep the jail out of the Ward 6 neighborhood.

As head of the Capitol Hill Prison Task Force, longtime resident Flossie Lee is one who fought long and hard against this site for the Correctional Treatment Facility, joining with others who felt their community was becoming the dumping ground for too many institutions and their attendant problems of noise, congestion and crime.

The task force's last-ditch stand ended when a federal appeals court panel here ruled that the old Gallinger Hospital, which formerly occupied the site and was the District's original facility for indigent medical care, was not protected as a historic landmark and could be torn down.

Today, Lee praises the Department of Corrections for listening to residents' concerns and involving them in programs the new facility is proposing for soon-to-be-released inmates.

"After we found out that it was going to be there, we weren't mad," Lee said. "We began working to help the community with their ills."

One way has been to get residents to participate in a so-called after care pilot program, underway for 36 Lorton Correctional Center inmates, which in its permanent form will be a major component of treatment at the new facility.

The year-old pilot offers instruction in areas ranging from reading, fatherhood and the family to nutrition and physical fitness. The idea is to give inmates some life skills they will need to adjust to the outside world. A key part of the program will be a network of counselors and community residents who can offer the inmates support in the months immediately after they are released.

Lee, who said the after-care programs have worked "wonders" in other areas, said many on the task force are ready to work with the inmates to ensure that when they go to "work and live in their neighborhoods, somebody will care about them."