BECAUSE THE LAST years ought to be the peaceful years, the 118 residents of St. Joseph's Home for the Aged on H Street NE will soon be moving out of Washington. The noise, fumes and disruptions caused by the construction of the new H Street overpass have become too much for the elderly men and women under the care of the Little Sisters of the Poor. The problems range from the predictable one of rats coming into the building from the construction site, to the frequent difficulty the sisters have in hearing their own prayers above the din as they try to answer the responses of the last rites at the bedsides of dying patients. Like a hovering behemoth of cement and steel, the overpass is so close to the front of St. Joseph's that the main entrance has been permanently closed.

Sacrificed to a highway, the sisters deserve praise for not leaving the city entirely. The residents of the home will be temporarily relocateld in one or another of the 39 nursing care facilities operated by the order around the country. When a new home is built in Washington - one is planned for a site near Providence Hospital - the sisters will welcome back those who have been displaced and also take in those currently on the waiting list. The sisters themselves, used to penance, are remaining at St. Joseph's for now - braced against the pollution and confusion as they seek to raise funds for the new operation.

In Washington for 106 years, St. Joseph's has been offering care to citizens whom few other service agencies go near. It is belaboring the obvious to say that pushing out the sisters is a strange way for the city government to express its gratitude for a century of service. For their part, the sisters are wasting no energy on resentment. Instead, they are going about the slow work of raising the $4.5 million needed for a new home. It is a benefit to the city that the sisters' reasons for staying - the elderly poor - are more pressing than the reasons for leaving.