While angry protesters were outside shouting "dirty politics," Montgomery County officials tried once again yesterday to assure county residents that the controversial Laytonsville landfill will not endanger the county's water supply.

"I can assure you, with the strong concurrence of the state, that this facility will be safe," County Executive Charles Gilchrist told a news conference.

Appearing with Gilchrist were Council president Ruth Spector, council member Neal Potter and William M. Eichbaum, a Maryland Department of Health and Mental Hygiene official who said he was confident that "there should be no concern for public health or environmental degradation," and praised the county for its extensive planning.

County officials also gave assurances that the water table would never rise to the level of the landfill, and that there was a sufficient layer of soil to prevent waste from seeping through bedrock fractures.

The 550-acre site, which could receive its first waste shipments as early as next April, sits in the Montgomery countryside near the Hawlings River and has been the focus of several heated political and legal squabbles ever since it was considered the prime location for a landfill in 1978.

While fighting a losing battle to obstruct the landfill, citizens groups have argued that waste from the site will contaminate their wells and the entire local water system and hired their own experts to counter claims by state and county officials about its safety.

Gilchrist said a technical response team has been formed that to answer questions about the environmental and public health impact of the landfill, along with a telephone line and answering service that will allows citizens to contact the county and record their questions.

He also called for the creation "of a public information program within the month to clarify community perception of the project." Other parts of the plan include an "informational booklet" describing safeguards and operating procedures. The county also plans to make documents availible to the public at the Sherwood Library.

Protesters outside the county government building in Rockville said these measures were not enough and were incensed at the fact that they were barred from the press conference. "We're not satisfied. We want to talk with them directly," said Cathy Garner, a Laytonsville resident.

"The County Executive is refusing to let us in. We challenge him to release all public data and technical information" on the landfill, said former Redskin Ray Schoenke, chairman of the political and community action committee of the Greater Laytonsville Civic Association.

Several council members also were upset that they were not invited to the press conference. When council member Rose Crenca began to ask a state official a series of questions raised by constituents, she was cut off by Gilchrist, who told her this was a session for the press.

Crenca, chairman of the county's committee on energy and the environment, said "I can really identify with the citizens now. This adds to a feeling of frustration and an aura of suspicion."