According to Webster's dictionary, an alewife is a small North American fish, resembling a shad, or a woman who operates an ale house. In Massachusetts, however, Alewife is also the name of a parkway running through the western part of Somerville. That's where the Metropolitan Boston Transit Authority (MBTA) is going to extend the Red Line from Harvard Square by 1982 or 1983, if everything goes according to schedule. Lucky for the Class of '82, things won't be too bad in the Square until March or April, when the heavy construction is scheduled to begin. But just wait until the Class of '83 arrives...

Like any other big construction project, the subway extension promises to be a big mess--"five miserable years of it," as officials in the Harvard Planning Office predict. But Harvard has its own committee to coordinate plans with the MBTA, and even though most Harvard students won't be riding the RedLine to Alewife, this process will have a big effect on their lives.

Right now, the Square isn't exactly ghosttown USA. In fact, any football game at Harvard stadium on your basic autumnal Saturday brings people in from all over. The businessmen thrive on the crowds who cram into the various muffin/coffee shops, shoe stores, chic boutiques and bookstores. Although the next five years will be painful, the merchants also are looking forward to the Square's new facade.

When it's all over, the sidewalks in both the Brattle Square area and on Massachusetts Avenue will be expanded to almost twice their normal size--providing more room for the street musicians as well as pedestrians. The plan is to push all the traffic lanes into the center, thus widening out space along the street In addition. changes will be noted at the regular kiosk stop. The architects, Skidmore, Owings and Merrill, have come up with a snazzy-looking station that overall resembles the fifth floor of Macy's on a slow day. The old entrance at the kiosk will be completely converted into a newsstand, and the new entrances will be at the Square, Church Street. Facilities will include a special elevator for the handicapped at all station stops.

The majority of the construction work in Harvard Square will take place underground, and two traffic lanes will remain in use the whole time. The tunneling work will go above ground only at one point--at the intersection of Mass Ave and Garden Street. The tunneling will begin sometime in March, Supratik Bose, chairman of the Harvard committee which is working with the MBTA, says.

The kiosk will not be its own familiar site in the Square during the construction period. In stead, passengers will stop in front of the Yen Ching chinese restaurant on Mass Ave, and descend into the subway in front of Holyoke Center. Another stop at the Kennedy School of Government will also include buses, and word has it that the new occupants of this building are not exactly looking forward to the location of the temporary stop.

The bulk of the Red Line project will be funded by the MBTA, supplemented by the Urban Mass Transit Association. Final costs for the project are expected to be in the millions, although no final figure has been estimated yet.

And, by the end of 1978, it is expected that the Red Line will be able to carry passengers from Harvard Square, to Porter Square, up past the city dump, to the aforementioned Alewife.

As the tunnel heads north under Mass Ave, it will gradually slope from its Harvard Square depth of 20 feet below street level to more than 100 feet below Porter Square, passing through bedrock much of the way.

Then it will rise gradually to a 50-foot depth at Davis, and continue upward to 20 feet at Alewife. Much of the excavation will be what is known in the trade as a "bored tunnel"--the digging proceeds entirely underground, with access through several shafts along the way. Toward Alewife, construction will be of the "cut-and-cover" variety, although the trench may be temporarily covered to permit street traffic to pass unhindered.

This cover, called "decking," may be of timber, metal or concrete. After construction is complete, it is removed and replaced with a permanent surface.