A Prince George's County councilman told College Park officials last night he had devised a compromise that would end that community's opposition to the existing plans for the northern leg of Metrorail's Green Line--opposition that might delay subway construction.

County Councilman James Herl told the College Park City Council the compromise would add at least $15 million in subway construction costs, but said he believes it is a "workable solution" that will win backing from the County Council and that would eventually be funded either by the county or the Washington region. Metrorail service is not scheduled to be extended to College Park before the 1990s.

Herl said College Park's acceptance of his plan would prevent a dispute over the northern Green Line route from delaying construction as a dispute over the line's southern alignment has done.

Under pressure from city residents, the College Park council voted in April to ask the County Council to move the city's proposed Metro station from Calvert Road to Erco Field, just north of Riverdale. The Calvert Road station would be served by a rail line raised above the ground, and its opponents complained that it would detract from the neighborhood of Old College Park and require construction of a raised highway through another part of the city.

According to Herl, College Park's request prompted opposition from the County Council, the county executive's office and officials in Riverdale and Greenbelt.

Herl, who represents both of those cities, said he would not take College Park's request to the County Council without compromise from all sides since it would shift the site of the proposed stations at Prince George's Plaza and Greenbelt.

The plan Herl proposed last night would keep the Green Line's original alignment intact but is designed to eliminate objections from College Park by keeping almost all of the line underground until well past the city's southeastern residential section and shifting the site of the raised highway to Riverdale.

"I think this is a workable solution," said City Councilman Chester Joy, who has led the opposition to the Calvert Road station. "It addresses the major concerns of the residents in this area."

Joy and City Councilman Joseph Drewer plan to cosponsor Herl's proposal at next Tuesday's City Council meeting, apparently assuring its passage.