Eighty-four employes of the Office of Personnel Management will pick up their travel pay today and then leave Monday for Mississippi to serve as federal observers in a primary runoff election the next day for various state and local offices.

The Washington-based staffers will join 260 colleagues from OPM offices around the country to observe and report how the election goes in 12 counties.

For some of the OPM aides, working under the direction of the Justice Department, this will be their third trip to Mississippi this year. Monday they will be briefed by local OPM officials and the Justice Department. They will take up their posts Tuesday--staying on overtime if necessary--to watch the voting and write a formal report on any irregularities they observe.

OPM poll-watchers were also in Mississippi in June to observe registration and again earlier this month for the first-round primary voting. There have been numerous allegations that local state officials had made it difficult for blacks to register and vote.

Employes of the Civil Service Commission (now the OPM) were first used as federal observers during the early 1960s when President Johnson sent them into several states in the south. All of the workers volunteered for the assignment, and some of them are retirees recalled by OPM because they have done the work before.

The OPM observers will be assigned to the counties of Benton, Bolivar, Grenada, Holmes, Humphreys, Lowndes, Noxubee, Quitman, Washington, Yazoo, Sunflower and Jasper.

OPM anticipates that an even larger contingent of workers will be sent to Mississippi in November to keep an eye on the general election.

Jobs: Interior in Herndon has openings for a personnel clerk, Grade 4 or 5, and a personnel assistant, GS 6/7. Call Gail Howell at 435-6265.

Social Security Administration in Arlington needs several clerk-typists, GS 2, 3 or 4 for permanent part-time work. Call 235-8591.

Federal Emergency Management Agency is looking for temporary and permanent personnel staffing specialists and a position classification specialist, GS 11/12. Send applications to Gerald Wood, FEMA personnel, 500 C St. SW, 20472.

Drug Enforcement Administration needs a secretary (typing) GS 5. Call Marian Potter at 633-5488.

Commerce in Georgetown wants a clerk-typist, GS 4/5. Call Shirley Lyon at 634-7402.

Census in Suitland has an opening for a clerk-steno, GS 4. Call Judy Selock at 763-7460.

Federal Highway Administration is looking for a professional welding engineer (bridge design and metallurgy experience) at the GM 13/14 level. Talk to Alicia McPhie on 426-2742.

Merit Systems Protection Board needs a payroll clerk or payroll technician, GS 4/5/6 (temporary duty, status only); and two accountants, GS 11/12 (status only). Call Theresa Gore at 653-7123.

Internal Revenue Service chief counsel's office wants a GS 5/6 secretary. Call Margie Collins on 566-3106.