Community was pitted against community last night as more than 300 people jammed the Montgomery County Council Chamber for a vituperative, unruly hearing on plans to build a giant incinerator to burn the county's trash.

Laytonsville residents turned out in force, fearful and angry that council members would reverse a 1987 decision to build the incinerator, a move that would mean continuation of a landfill in their community.

Residents of Dickerson, the rural upper county enclave where the county plans to build the $250 million trash-to-energy burner, were there to repeat their message that the facility would be economically unwise and environmentally harmful.

Residents of the tiny town of Boyds showed up to support the incinerator over a plan that would see land in Boyds mined for rock and the resulting quarry filled with trash.

Fire marshals turned people away at the door to the Rockville meeting room when the capacity of 314 was reached. The spillover went into a conference room where the meeting was shown on television.

Against a backdrop of placards and buttons, the crowd shouted and booed and hissed. There was a battle of jeers and applause as each speaker testified. Council members were badgered and insulted -- reminded again and again of the upcoming elections that could sweep them from office.

"I'm going to insist on civility," Council President William E. Hanna Jr. (D) warned as he threatened to adjourn the meeting.

Council member Michael L. Gudis (D) got into a testy exchange with Del. Jean W. Roesser (R-Montgomery), who spoke against the incinerator, as he challenged her to tell him "what do we do . . . with the garbage?"

Dickerson resident Karen Kalla, who heads the Sugarloaf Citizens Association, said she was disturbed to see neighborhood was pitted against neighborhood. She said her group had worked in the past with Laytonsville residents, and said she was upset with the "back-stabbing."

Residents of Laytonsville, where the county operates the Oaks Landfill, noted that the county promised them a decade ago that it would close the landfill. A decision against building the incinerator, they said, would in effect sentence them to continued life with a trash dump.

The council voted three years ago to build the incinerator in Dickerson, but the decision is being reexamined because the council is reviewing the contracts that provide the legal and financial framework for the project. The council is expected to decide in July.