FOR CITY COUNCIL, the tough part of tomorrow's scheduled vote on whether to let nonunion laborers work on the $700 million Convention Center expansion won't be facing angry union members if the measure passes.

The toughest part? How to monitor whether black and minority workers and contractors have really been hired and are actually on the job - and are not just figments of a general contractor's active imagination.

Councilman Frank DiCicco, who sits on the board of the Convention Center, proposed an amendment to the Convention Center Project Economic Opportunity Plan when it became clear that there is little minority representation on the largest public-works project in state history.

Minorities make up about 55 percent of the city population, but are essentially nonexistent in the city's skilled-trades unions. When pressed for a racial and gender breakdown of the Building Trades Council, Pat Gillespie, the council's business manager, came up empty.

Oh, those pesky minority numbers. General contractors on projects, like the Convention Center, that require "good" and "best faith" efforts to hire minorities can just shrug and say, "Well, we tried but we couldn't find any that qualified."

The aspirational goals for the Convention Center project: 25 percent black, 10 percent Hispanic, 5 percent Asian and 10 percent female in the construction workforce. It also requires that 50 percent of the workers be local residents. Perhaps we can see fewer New Jersey license plates at construction sites.

Through the amendment, Council wants to reduce any excuses about not being able to hire minorities. It would permit nonunion employers to bid on contacts, making the pool of minorities wider and deeper.

Although the amendment includes procedures for oversight, including on-site visits twice a week to record minority and female participation, and monthly reporting, the lack of enforcement powers means this monitoring doesn't have teeth.

Is this amendment the best solution to this intractable problem? No - the best solution would be an honest effort on the unions' part to widen their minority base. But relying on the conscience of contractors in Philadelphia to do the right thing has proven to be a huge mistake.

Council startled a sleeping giant that is used to having its way and winks at any attempt at oversight. It was a gutsy move in a strong union town, and shows Council's determination to change the old way of doing things.

Council's resolve will be tested tomorrow. By then, union honchos will have swooped in to lobby the lawmakers. And Council members will have had time to look at the big picture. Still, that picture continues to have few blacks in city construction jobs.

The vote is expected to be close.

Council must stick to its guns and pass the amendment. Put the city's construction unions on notice that excluding blacks and other minorities is no longer acceptable. *