A tugboat company manager has been indicted in federal court in San Francisco on charges of polluting the Sacramento-San Joaquin River Delta by dumping dredged materials into waters near Pittsburg.

Mark Guinn, 41, of Elk Grove, the general manager of Northern California operations of Brusco Tug & Barge Inc., was indicted by a federal grand jury Tuesday on four counts of violating the U.S. Clean Water Act.

He is accused of dumping or causing other company workers to dump dredged materials directly into Delta waters surrounding Winter Island, northeast of Pittsburg, three times in 2003 and once in 2007.

Brusco, based in Longview, Wash., has a fleet of tugs and barges used for towing and disposing of dredged material generated during various dredging projects.

Winter Island, the site of an unsuccessful utopian community in the 1890s, is a privately owned 453-acre Delta island now used for wetland habitat and a duck hunting club.

Brusco had a contract to dispose of dredged material on the island, for a fee, for use in levee maintenance, but had no permit to dump the material in the water, according to the indictment.

Each count carries a possible maximum sentence of three years in prison, but the actual penalty, if Guinn is convicted, would be determined by a judge after consideration of federal sentencing guidelines.

U.S. attorney’s office spokesman Jack Gillund said no date has been set yet for Guinn to appear in court.

The case was assigned to U.S. District Judge Susan Illston.

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