The Coast Guard cutter Morgenthau, berthed at Coast Guard Base Sand Island, dumped 4,600 gallons of sewage and other waste water into Honolulu Harbor, the Coast Guard confirmed Tuesday.

The state Department of Health’s Clean Water Branch reported the spill Monday night.

Signs warning people to stay out of waters on the Diamond Head end of Sand Island State Park were posted Tuesday.

In a written statement, the Coast Guard said a regulatory valve on cutter Cutter may have been left open since Friday when the vessel docked at Sand Island at 6:30 p.m.

In the 63 hours since mooring, the ship’s sewage system, which is set to pump when the holding tank reaches about 1,250 gallons, had automatically discharged four times. The contents of the tank include wastewater from the sinks and showers and whatever sewage is produced.

The health department estimated that 4,600 gallons of waste water were dumped into the harbor.

The Coast Guard said  a crewmember aboard the  Morgenthau reported the smell of sewage at 9:30 a.m. Monday.

A ship’s officer went to the side of the ship and saw  brown water flowing overboard through the sewage discharge port intended for use only at sea and immediately secured the system.

 The officer determined the cause of the improper discharge to be the misalignment of the overboard discharge valve which was locked in accordance with the procedures for entering port, but was incorrectly in the open position.

"As one of our missions is to protect the environment, I take this very seriously," said Capt. Richard Mourey, commanding officer of Cutter Morgenthau. "We will take the necessary steps to ensure this does not happen again."