LARGE, EXPENSIVE projects have a way of building up momentum, especially once they are well underway--as is construction of Harvard's $110 million medical Area Total Energy Plant. Work on the plant's foundation is continuing over the protest of many community groups in the Mission Hill area that have raised serious questions about the wisdom of building a generating facility on the edge of the residential neighborhood.

Although work proceeds regardless of the community's reservations, state officials empowered to halt the project have had more success in gaining consideration of the public interest, threatening to block the project if planners did not provide concessions that would limit the plant's emissions. Officials in the state Division of Air and Hazardous Materials should be commended for their extended efforts to overhaul the plant's design and to exact an agreement from Harvard to restrict the allowed emission level of nitrogen dioxide, a pollutant that can irritate the respiratory system.

It was only after division representatives threatened to block the project that plant officials reevaluated their design and discovered last week that it would indeed be possible for the plant to meet the division's recommended limit.

The interested public now has a month to comment on the division's preliminary decision before it becomes final. In view of the tremendous impact on public health that a large generating facility might have, the next month should serve as a period of very critical re-examination.