The Harvard Square Development Task Force last night at a public hearing presented a series of alternatives for the proposed extension of the MBTA red line north of Harvard Square.

The plans call for an extension of the line to run to Porter Square, to Davis Square, and then to a terminus at Arlington Heights.

A report prepared by the Cambridge Department of Planning and Development lists eight possible plans for the extension from Harvard Square. One set of proposals would continue the present line up Mass Ave to Porter Square.

The other set calls for the line to run to Brattle St., down Mt. Auburn St., underneath the Radcliffe Quad and then up Mass Ave.

Robert A. Bowyer, director of the Cambridge planning dept., said last night that more technical information is needed to determine what effect the construction would have on Radcliffe, if that route is chosen.

Bowyer said one engineer thought buildings over the line might sink as much as six inches, depending on the soil conditions.

The report also said there might be noise-vibration problems near the Loeb Drama Center if the line ran along Brattle St., but Bowyer said he could not estimate how serious that would be.

A local firm will conduct an environmental impact study on the proposed lines next month. It will submit its recommendations to the MBTA next fall.