State transportation officials said tonight they will shut the Arboretum-bound side of the Casey Overpass in February, followed by the Mattapan-bound side by the end of March.

And then, officials said at a meeting at English High School, contractors will bring in the heavy equipment to begin tearing down the decaying span - built high enough to let an elevated train pass underneath - to replace it with a series of surface roads and rebuilt intersections, which will include squaring Shea Circle. Over the 2 1/2-year project, the Forest Hills T stop will also get an overhaul that will include a new entrance near where the 39 bus now stops, but won't at the end of the work, because its berth will be moved to an expanded upper busway along Washington Street.

Officials spoke before a packed audience that included large numbers of vocal opponents who made their point of wanting the overpass replaced with another overpass by repeatedly calling state officials liars and hacks who couldn't even figure out how to turn on most of the lights in the school auditorium.

Before the meeting even started, bridge supporters chanted "Forest Hills! Keep the bridge!" During the meeting, they were not above using obscenities to make their point that the state surface-road plan will leave them choking in traffic and possibly breathing in asbestos and silicates from the construction work. State officials acknowledged not testing the bridge for asbestos, saying construction companies had stopped using asbestos by the time the overpass was built, but said they would check into it and the silicate issue.

State Rep. Liz Malia jumped in, saying the Patrick administration refused to listen to residents and urging the state employees at the meeting to talk to Gov. Baker and his new transportation secretary to listen to them.

However, with the state decision to go with surface roads made years ago, planners generally declined to meet the bridge supporters in their verbal joust, saying they would only talk about construction work over the next 90 days, not rehash the decision to go with what they said was a cheaper option.

Project planners said that before they shut the lanes, they will add three lanes to the existing surface road that runs from Shea Circle to New Washington Street to handle traffic forced off the shuttered overpass, which they said desperately needs to be shut because it is structurally unsound, from what's left of its deck to the foundations that anchor it in the ground.

Along with that, traffic engineers will look at resyncing the signals around the road and will remove mid-block crosswalks on Washington and New Washington, which they said can now throw traffic cycles into a gridlocked tizzy because they are not connected with the signals at intersections.

Courthouse parking will be relocated to the MBTA bus yard behind 500 Arborway. Temporary sidewalks and crosswalks will be added.

A temporary lengthening of the upper busway will let the 39 pull in there as its current parking area - left over from Green Line days - can be turned into a road.

Planners said that in 2015, Orange Line riders could see weekend bustitution and an early end to service on a number of days in 2015 to allow for work at Forest Hills station.

In addition to replacing the overpass, the new project will remove some of the gyrations drivers now have to go through to navigate the area, for example, trying to get to the West Roxbury courthouse from Washington Street, they said.

During demolition and construction of the new roads, they continued, police details will help traffic move better - as will BTD traffic-enforcement officers, who will roam the area looking for double parkers and other traffic miscreants, who will be encouraged to move along - at the point of a ticket, if necessary.

Overall, the work will free up enough land for 1.5 acres of parkland, to be split among four park areas. All of the roads will get bike lanes - which will let somebody bicycle from Roslindale Square to the Back Bay. Some of the bike lanes will even have crosswalks for pedestrians.