SEATTLE, Oct 30 (Reuters) - A Washington state man accused of using an excavator and a bulldozer to try to alter the Tahuya River was charged on Thursday with environmental violations, the state's top attorney said.

William Cayo Sr. was charged in Mason County District Court with violating water pollution and shoreline management laws as well as conducting unpermitted hydraulic activities in February 2013, Attorney General Bob Ferguson's office said in a statement.

Federal biologists concluded that about 5,747 square meters of river bed were moved to fill the active channel or otherwise alter the streambed conditions in the river, about 50 miles west of Seattle, Ferguson said.

Under Washington state law, a property owner can work with a county and other agencies to develop "responsible, professional and effective" hydraulic or shoreline projects that protect both private property and natural resources.

"Unpermitted and improperly designed work in a riverbed or on a shoreline, however, can damage neighboring properties, pollute the river, and kill fish," the statement said. (Reporting by Eric M. Johnson in Seattle; Editing by Peter Cooney)