A federal judge fined a New Jersey company $100,000 after it pleaded guilty Friday to environmental violations in Cecil County. Appearing before U.S. District Judge William M. Nickerson in Baltimore, Hartford Associates admitted that it negligently filled wetlands on a 375-acre property the company owned south of U.S. 40 and north of Frenchtown Road in Elkton. An ecologist with the Army Corps of Engineers said that the damage caused by Hartford could have destroyed more than 50 acres of wetlands had it not been discovered. "This is a story of a developer who has much previous knowledge of the federal wetlands permit program and went ahead anyway without permits," said Alex Dolgos, the ecologist. He said that Joseph Samost, Hartford's owner, also has been cited for wetlands violations in New Jersey. The Cecil County case was investigated by the Corps of Engineers, the U.S. Environmental Protection Agency and the FBI. Prosecutors said Hartford altered the property after becoming concerned about a new state law that would tighten wetlands restrictions. Mr. Samost hired contractors who brought in excavation equipment, cleared trees, dug new drainage trenches and adjusted streambeds. The work was done without permits or guidance from the Corp of Engineers or other authorities, prosecutors said. The soil that was excavated was dumped in wetland areas. The result was extensive sediment runoff from the property into Perch Creek. The corps became aware of the work in January 1991 and ordered it stopped. The company was required to restore the property and has done so. "It will take a while to recover totally, but it's well on its way," said Mr. Dolgos. Carl Poplar, a New Jersey attorney for Hartford, could not be reached for comment. The case was prosecuted by Assistant U.S. Attorneys Ethan L. Bauman and Robert M. Thomas Jr.