Lt. Col. Joseph Vasco, whose 20-year career with the Prince George's County police ends today, will begin work for the county next week as a consultant overseeing construction of the county's new detention center.

Tim Ayers, spokesman for County Executive Parris Glendening, said the idea for the contract originated with Glendening's chief administrative officer, John Wesley White.

"John Wesley and Parris wanted to do it after word got out that Vasco was going to retire," Ayers said. "He's an experienced administrator and manager. He will be making sure the money is accounted for, that the program stays on track. We figured this was the cheapest way to do this and still get a good person."

Vasco, 48, had lobbied unsuccessfully to become chief of the county's 900-member police force, but Glendening bypassed him after several black community leaders said they would oppose the appointment.

Earlier this week, Vasco was granted permission to retire on medical disability because of injuries he received in a 1980 car accident. His last day on the police force is today.

Ayers said Vasco will be paid $30 per hour for what is expected to amount to 30 to 40 hours of work each week. Because he will not be an employe of the county at that point, he will draw no additional pension or insurance benefits. He will, however, begin to draw the pension he is owed because of his disability retirement--70 percent of his estimated $52,000 per year salary.

Vasco said privately that he was deeply disappointed that he was not appointed chief, but Ayers said that the consulting arrangement, which will run for the 30 to 36 months projected to build the jail, is not an effort to "patch up hard feelings."

"Parris has a great deal of respect for Vasco," Ayers said.

Vasco, who briefly headed the county's Department of Corrections in 1979, will coordinate the details of constructing the county's new $40 million jail, which Ayers called "the largest public works project the county's ever done."

Prince George's is under a court order to relieve overcrowding at its facility in Upper Marlboro, a jail built to hold 143 persons in single cells but which has sometimes held more than 500. The new jail will be located on Brown Station Road in Largo, more than a mile from the current facility, and will house 500 to 600 prisoners in single cells.

Although state funds for the jail have been approved, construction has been delayed while the county selected a new corrections chief and worked out problems in the design. Most of the work on the new jail has been lead by White, who told a reporter several months ago that he was concerned that he was not spending enough time on the project. It is an effort that involves several departments, local judges and several funding sources.

Corrections department head Samuel Saxton said he has "no problems " with Vasco's new appointment. "I know what I want and if Joe can get it done fast, I have no problems with who carries the shovel," he said.

Vasco said he hesitated before taking the appointment. "I had to feel it was something I'd be interested in and that it was something I would be good at. They told me they wanted me to serve as a manager, to work with people. I said, 'This is right up my alley.' "