The settlement between the Issaquah, Wash.-based retail giant and the Environmental Protection Agency also requires Costco to install a wastewater treatment system at the Kailua-Kona location.

"Today's settlement is part of our continuing effort to close large capacity cesspools and protect drinking water sources on the Big Island," said Alexis Strauss, director of the EPA's water division for the Pacific Southwest region. "We will continue o encourage all large capacity cesspool owners to meet the requirements by closing large capacity cesspools promptly."

Costco is required to:

— Install dual chamber septic tanks with effluent filters and grease interceptors on their injection wells that receive food processing wastewater.

— Monitor wastewater quality before and after treatment for at least six months to determine if treatment is working.

— Provide periodic reports to the EPA on wastewater quality.

Large capacity cesspools, defined as one that discharges untreated sewage from multidwellings or nonresidential location that serves 20 or more people on any day, have been prohibited since April 2005 under the Safe Drinking Water Act.

Cesspools discharge raw sewage into the ground, which can lead to disease-causing pathogens and other contaminants entering the groundwater, streams and the ocean, the EPA said.

Cesspools are used in Hawaii more than any other state.