Governor Volpe's promise last week to send a special message to the General Court in order to expedite construction of the Kennedy Library could be an important first step in ending the impasse that has postponed ground-breaking for three years.

But a special message to the legislature is not enough. Statements by Dorchester and Milton politicians last week indicated that the proposed bill will be in for a tough fight on Beacon Hill. The Governor must show the state now that he is willing to keep applying pressure even if the political consequences appear damaging.

Volpe's message recommends a marshland area on the Neponset River near Dorchester and Milton, now owned by the MDC, as the site for a new $6 million MBTA transit facility. It would replace the Bennett St. yards in Cambridge, the planned site for the library. It is clear that the marshland area is the best location for the new yards in metropolitan Boston. The results of a survey, to be released this week; show that no houses will be destroyed and no town lands used up. Earlier surveys have shown that the 12-acre Bennett St. site is the only are near the University capable of handling the Library complex. Furthermore, the MBTA, the General Court, and the Governor have repeatedly gone on record supporting the Library in Cambridge as a memorial to the late President Kennedy. State funds have already been committed to purchase the Bennett St. land for the Library as soon as the land becomes available.

The long search for a new transit site has badly hurt the Library and the University. Both have several million dollars tied up in the project, and, while they are forced to wait, costs are rising. People across the country who have donated money to the Library are growing impatient and disillusioned. Worst, of all, the Library and its educational facilities, of great value to historians and political scientists alike, cannot be used.

The Governor faces strong opposition. Last summer Dorchester residents were able to block the use of another site for the transit facilities near Codman St. in Dorchester. They feared that the yards would lower property values and ruin the neighborhood. Milton town officials contend that the yards would fill in valuable and scenic wildlife refuge and, worse, connect Milton by land with Dorchester. Milton residents, mainly of middle and upper incomes, fear being closely tied to poorer areas in Boston. These objections will make the fight over the marshland an emotional one. But the Governor himself has said that he has made a moral commitment to the Library. Now he has made a legislative commitment. He must carry it through.