Federal workers who fear that Social Security may eat into their retirement system need to watch the progress of two important amendments the Senate will take up when it begins debate today. The changes are designed to protect federal workers while still keeping afloat the system most other Americans pay into from the day they are hired until they retire.

One feature of the Social Security financing plan, which cleared the House 282-148, would require that all federal workers--from presidents to postal clerks--hired after next January be covered by Social Security as well as the civil service retirement plan.

Current employes would remain outside the Social Security system.

All of the 180,000 people the government expects to hire next year would be required to contribute 6.7 percent of their salaries to Social Security, as well as make the 7 percent contribution to the civil service retirement program.

Federal employe and retiree groups have been waging a desperate battle to keep new federal workers from being rolled into Social Security.

They contend that putting new feds under Social Security would strangle the flow of contributions into the federal pension system and/or be the first step toward mandatory Social Security coverage for the 2.8 million people already working for the government.

Organizations that want to keep feds outside the Social Security blanket are backing an amendent that will be introduced by Sen. Russell Long (D-La.). He is the ranking minority member of the Senate Finance Committee, which writes Social Security legislation.

Long wants to delay putting new federal and postal employes under Social Security until next Jan. 1, or until a supplementary civil service retirement plan is put in place for them, whichever is later.

The effect of the Long amendment (which the Finance Committee defeated on a 10-6 vote) would probably be to kill Social Security coverage for feds. The thinking is that powerful federal and postal unions next year (an election year) could persuade Congress to drop the idea of bringing new government workers into the system that covers most other American workers.

Sen. Ted Stevens (R-Alaska) will introduce an amendment that would--if new feds are put under Social Security--give them the option of paying only into the Social Security system until a new government staff retirement plan is set up for them. Those employes would become part of the new plan when it is established, and the government would make contributions to the civil service program for the time they had been in government.

Stevens says he opposes mandatory Social Security coverage for feds, but like many people, he thinks it is inevitable. He thinks his amendment would help the government recruit new workers, if Social Security becomes mandatory, by sparing them from having to pay the full freight--13.7 percent--for both Civil Service and Social Security.