Back wages for thousands of federal engineers, scientists, medical personnel and others in special-pay occupations will be the subject of arguments tomorrow morning before U.S. District Judge John Garrett Penn.

If you are a special-rater, a word of caution: Don't spend the money.

At issue is how much the federal government owes those special-raters for raises, or parts of general pay raises, denied them from 1982 through 1988. During those years, the special-raters (who are paid anywhere from 2 percent to 30 percent more than other workers in the same grades) didn't automatically get the full January raises that went to non-special-rate U.S. workers.

The National Treasury Employees Union wants full back pay. That would cost many millions of dollars. An appeals court told the union and the government to reach a settlement and asked the district court to oversee the process.

The issue is complicated. Some workers got parts of raises. Some have changed jobs, died, retired or changed their names because of marriage or divorce. Figuring who gets what, and where to send the check, promises to be a nightmare.

Nobody knows how much money is at stake. But during the years in question, rank-and-file workers got 4 percent raises in 1982 and 1984, a 3.5 percent raise in 1985, a 3 percent raise in 1987 and a 2 percent raise in 1988.

The case has been in court for years. Nobody knows when it will be settled. But this may be a clue that it will be later rather than sooner: The union has a hot line (202-785-4436, ext. 606) to keep folks advised on developments. But while most hot lines are updated daily, if not hourly, the back-pay hot line is updated every 30 days.

Sick Offices

The American Federation of Government Employees is sponsoring an office health and safety conference this week at the George Meany Labor Studies Center in Silver Spring. David Schlein, national vice president for the Washington area, wants white-collar government operations to get the same kind of checkups and safeguards as industrial operations.

This week's session will train local union leaders to spot potential hazards at the office.

Job Mart

The Washington Navy Yard will sponsor a clerical/admin- istrative support job fair from 11 a.m. to 6 p.m. Feb. 22 and from 9 a.m. to 2 p.m. Feb. 23. For details, call Debra Torres at 202-433-5370.

Andrews Air Force Base has temporary openings for clerk-typists, GS 2 through 4, and a secretary-steno, GS 4 through 6. The special-rate jobs start at $15,190 to $25,860. Call Helen Busi at 301-981-4581.

Sweet Charity

The Office of Personnel Management's inspector general will take a look at what happens to the millions of dollars charities get each year through the Combined Federal Campaign. In 1989, federal- postal workers gave $186 million to several hundred groups in the campaign through payroll deductions. The inspector general's office, headed by Patrick McFarland, will audit about 50 organizations each year and report to Congress.