The guilty pleas entered in federal and state courts by a Maryland waste hauler may have implications for a pending proposal for a trash transfer station in Charlotte Hall, according to participants in the debate over whether to build the facility.

Last week, Albert W. Stevens, his two sons and a daughter-in-law pleaded guilty to federal fraud and state environmental charges stemming from the disposal of trash hauled from area Navy bases. The Stevens family agreed to pay $3.5 million in federal fines and penalties, in addition to $80,000 each to Prince George's and St. Mary's county governments.

In the scheme described in court documents, the Stevens family, operating as AW Stevens & Sons Disposal Systems Inc. and St. Mary's Disposal Systems Inc., set up phony recycling centers in the two counties, operating them instead as waste transfer stations.

St. Mary's Disposal Systems Inc., now defunct, was purchased by Waste Management of Maryland Inc., the county's largest waste hauler.

Bill Mattingly, a former manager with St. Mary's Disposal Systems Inc., is now employed by Waste Management. Last week, on the same day that the Stevenses were making their guilty pleas in multi-court appearances, Mattingly resigned from the county's Solid Waste Advisory Committee, a panel involved in local policy on trash disposal. Mattingly said he was taking the step "to avoid the appearance of a conflict of interest."

Mattingly's past involvement with the Stevens family and the firm that operated the illegal transfer station on Andrew's Church Road raises questions about a proposed new Waste Management facility, said Larry Pinto, a board member and former president of the Community Preservation Coalition of St. Mary's, a citizens group.

Waste Management wants to build a transfer station in Charlotte Hall that would receive 400 tons of trash a day from Southern Maryland for eventual trucking to mega-landfills in Virginia. Mattingly has been a spokesman for the firm on the proposal.

St. Mary's Disposal Systems "admitted to operating an illegal transfer station," Pinto said of the now-defunct firm purchased by Waste Management. "They've falsified [federal] records, and they've paid fines for these violations and now we're supposed to believe that the . . . same operation will run a legitimate facility?"

But Mattingly and Waste Management officials asserted such questions ignore the firm's national record.

"We operate these facilities all over the country, legally and professionally. We cut no corners," said Ron Adolph, district manager for Waste Management. "What we're proposing [in Charlotte Hall] is fully in line with [the county's] solid waste plan. It will be operated over and beyond the letter of the law."

Testimony from the county's zoning case against the St. Mary's Disposal Systems transfer station also has left some questions unanswered. The judge in the trial ruled against the county after the company successfully argued that the transfer station operation was "grandfathered" under zoning regulations because a previous property owner had operated similarly for years.

"The irony to me," said Ken Hastings, chairman of the county's Solid Waste Advisory Committee, "is in order to beat the county's case, they [St. Mary's Disposal Systems] had to admit, `We've been doing this all along, you can't stop us because it's grandfathered.' In order to beat that case, they had to admit things that were going to haunt them later on."

When called to testify during that trial, Mattingly invoked the Fifth Amendment, the constitutional protection against self-incrimination.

County officials familiar with the case suggested last week that Mattingly may have provided federal and state investigators with critical information that eventually led to the guilty pleas entered by the Stevenses.

"I cooperated voluntarily and completely with the investigators. When I was interviewed, I told them about how we operated at the site and the day-to-day operations," Mattingly said.

He said he invoked the Fifth Amendment on the advice of his attorney and not to avoid incriminating himself. He said he received no promises of immunity.

"I have not been charged and will not be charged with anything," Mattingly said.