The City Council last night threatened to sue the Massachusetts government to block construction of a proposed 28-lane highway interchange in East Cambridge, warning at a jam-packed meeting that the 11-story behemoth would devastate the city.

The council forwarded to its legal department an order calling on City Manager Robert W. Healy to take "any and all appropriate legal action" against the proposed project, part of the state's multibillion dollar plan to move the Central Artery in Boston underground.

"We will live to regret what you are doing to our city," City Councillor Edward N. Cyr told a representative of the state Transportation Department. "What you are removing from Boston you are putting twofold into the city."

The highway interchange--known as scheme Z--is the only remaining option for rerouting traffic through Cambridge which the state still considers workable. Although Transportation officials originally considered a number of alternative plans, department representative William Twomey said that Scheme Z was by far the most economical.

But in last night's three-hour hearing, seven of the council's nine members lambasted the plan, saying it would destroy parkland, cast a huge shadow over the surrounding neighborhoods and create excessive air and noise pollution.

Opposition to the plan also ran high among the approximately 60 city residents who attended the hearing.

"Clearly this is a citywide issue--not just something that impacts East Cambridge," said Debra M. McManus, chair of the anti-development group Cambridge Citizens for Livable Neighborhoods (CCLN). "The pollution generated will be measured in tons per day."

As an alternative to Scheme Z, McManus advocated a plan developed by Stephen Kaiser, a Cambridge teacher and former state transportaion engineer. Kaiser's plan calls for a series of tunnels built underneath the Charles to replace the interchange.

Dredged land from the riverbottom would be placed on the proposed site of the interchange to create a new park in East Cambridge--a change that he said would be a vast visual improvement over the 11-story ramp. ramp.

"With the scheme Z you would see this elevated spaghetti," Kaiser said.

Twomey argued that construction of these tunnels would cost the state from $800 million to $1.2 billion, as compared to the $400 million pricetag of Scheme Z. In addition, he said, the alternative plan would delay completion of the project by at least two years.

While he acknowledged that the project would have a "negative asthetic impact," Twomey said the state would mitigate these effects by constructing large areas of parkland around the highway structure.

He said that the project would also curb pollution in the city by drawing cars off city streets.

"Lots of traffic that should be on regional highways is on city streets. A lot of the traffic can be drawn out of city streets and on top of the Central Artery," Twomey said.

Several councillors drew parallels to the Inner Belt, a superhighway proposed in the late 1960s that would have run through Central Square. After years of friction with Transportation Department officials, the city ultimately managed to block that project.