Prince George's County's outgoing chief administrative officer has left his post to join a law firm -- and work for the county.

John P. Davey, the former top aide to County Executive Parris N. Glendening, will represent the county as an alternate to the board of directors of the Washington Metropolitan Area Transit Authority, Metro's agency, on a $115-an-hour retainer that could generate up to $115,000 a year in income for him and his law firm. He was paid $112,000 a year in his county job.

Prince George's is the only suburban jurisdiction that pays its nonvoting Metro alternates so handsomely. Montgomery pays its board member and alternate a flat fee of $10,000 each. Northern Virginia's board members get $50 each day they attend Metro meetings. The District pays former city auditor Matthew Watson about $30,000 a year to work half time on Metro.

Glendening, emphasizing Davey's knowledge of county needs and Prince George's major stake in where Metro's money is spent, said he will send Davey's name to the County Council Tuesday for confirmation.

"When you think about what's at stake," said Glendening, "you get one of the very best people you can find, someone with the capability, with the knowledge of government and decision-makers and of what we want done, and you put that person in to help."

"Obviously, there's a price tag associated with that. I think it's worth that money."

In 1984, Glendening hired former county attorney Robert S. Ostrum, at an initial hourly fee of $90, to serve as an alternate to the Metro board. The nomination was approved with only council member Sue V. Mills dissenting.

Ostrum's hourly rate eventually rose to $140, and the amounts he billed the county for his services ranged from $25,000 to $140,000 a year. Glendening said that is a bargain, even at a time when the county has had to reduce its work force by almost 900 positions to make ends meet in a depressed economy.

He said other counties have large staffs supporting their appointed representatives to Metro, but Prince George's has only one paid person.

When he named Ostrum, "The county had gone almost 10 years with no Metro construction," Glendening said. "We had to force a total renegotiation of the construction schedule, and we prevailed. We got $685 million for construction of the Green Line, moved it up five years. It was a tremendous victory."

Once again, Glendening said, "we've started on a series of whole new battles" in which Prince George's has much at stake.

Those battles include construction of the long-delayed Branch Avenue line into the southern part of the county, completion of the Green Line from Fort Totten to Greenbelt, and Glendening's proposal to extend the Blue Line from its current terminus at Addison Road three miles east to the Largo-Kettering area.

In addition to Davey, council member Hilda R. Pemberton is slated to succeed her colleague, Richard J. Castaldi, on the Metro board. "We're in an immense battle," Glendening said. "Hilda's very capable, but she's not able to put in 25 hours a week" on Metro business.

When he is not working on Metro matters, Davey said he will be doing commercial litigation work for the Calverton law firm of Nylen & Gilmore.