InA CITY WHERE POLITICAL UNITY is a rare phenomenon, the fight to stop a massive highway in terchange from being constructed in Cambridge managed to bring the together disparate interests that usually divide the city.

The story of Scheme Z--the 16-lane, 11-story highway project slated for construction in East Cambridge--is the story of a unique and almost unheard-of political coalition.

It is a coalition that appears to have succeeded. Last March a state-appointed committee recommended that Scheme Z be scrapped in favor of a smaller, more expensive plan.

State officials and the Bridge Design Review committee are nearing agreement of a compromise plan that is "better from a Cambridge perspective," according to Cambridge Conservation Commission Chair Elizabeth Epstein, a committee member.

The new proposal--dubbed 8.1D--would move the highway construction project farther away from the Charles River, lower the height of the roadways and reduce the number of highway ramps and loops by 30 percent, Epstein says.


The plan would also cut the number of miles of highway in half and extend subway and commuter rail lines.

But the improvement--which Stanley H. Durlacher, Assistant Secretary of Transportation and Construction says "strikes a fine balance between many interests"--will inflate the price tag of the project by $200 million. The final price tag will top $630 million.

The cost is significantly lower than the $840 million proposal the Bridge Committee offered last fall, which state administrators said would be far too expensive.

Final plans for 8.1D are months from completion, according to Epstein. The committee has yet to address 21 outstanding issues and complaints that were raised after the new proposal of 8.1 D, victory over the state and over Scheme Z.

Scheme Z was part of a plan to depress the elevated Central Artery underground. Under Scheme Z, four bridges over the Charles River would connect the state's newly depressed Artery with Interstate 93.

The Boston business community and state transportation officials, including former Secretary of Transportation Frederick P. Salvucci, plugged Scheme Z and said the plan was the best and most economical way of constructing the interchange.

But Cantabrigians complained that the Artery was being depressed in Boston at the cost of elevating an environmental monstrosity in Cambridge.

Activists argued that air pollution and traffic volume in the city would skyrocket if the project reached completion.

"The state wanted to do it cheap and dirty and they thought they could get away with it," says Debra M. Mc-Manus, co-chair of the Cambridge Citizens for Livable Neighborhoods--one the community groups leading the struggle against Scheme Z.

The opposition to Scheme Z led a lawsuit that pitted the city of Cambridge against the Commonwealth.