The Senate is expected to approve this week a twin-option retirement package for the 300,000 federal workers hired since January 1984. The House is also working on its own plan -- a single retirement option -- that should be ready for a vote by the middle of this month.

If Congress doesn't come up with a new pension system, those employes will have a 14 percent bite taken from their paychecks beginning next year.

None of the plans would be mandatory for government workers hired before 1984. And none of them would change benefits for those employes or for persons already retired. They would remain under the current civil service retirement system.

Only employes hired since 1984, who are also covered by Social Security, would be required to go into a new retirement system.

The two Senate options, by Sens. Ted Stevens (R-Alaska) and William Roth (R-Del.), are contained in one bill, and they would be open -- on a voluntary basis -- to employes under the current federal retirement system.

The House plan, by Reps. William Ford (D-Mich.) and Mary Rose Oakar (D-Ohio), would be limited to post-1983 hires.

The Senate and House proposals would base future retirement benefits on a combination of Social Security, civil service and earnings from optional investments or savings plans that would be tax-deferred.

Federal and postal union leaders prefer the Ford-Oakar bill, which last week picked up 50 cosponsors in the House, because it provides a better civil service benefit than either of the two Senate plans. It does not offer as generous a tax-deferred savings program as either Senate option.

Congressional insiders expect the Senate to take up and pass the Stevens-Roth plan next week.

The House Post Office-Civil Service Committee is expected to approve the Ford-Oakar bill sometime later and either send it to the full House for a vote or perhaps send it directly to a Senate-House conference committee.

Members of Congress have until the end of this year to set up a new pension system for new and future federal workers. Those employes are now paying the full Social Security tax (7.05 percent of salary) plus a little more than 1 percent of salary to the civil service retirement fund.

If Congress cannot agree on a new retirement system for them, those retirees will have to pay both Social Security and the full civil service retirement contribution of 7 percent next year.