The U.S Environmental Protection Agency has ordered a helicopter tour company on Kauai to close an illegal cesspool and pay $45,000 in fines.

EPA inspectors in 2018 found that Smoky Mountain Helicopters Inc., doing business as Maverick Helicopters, operated a large-capacity cesspool servicing the restroom at a leased airport hangar at Kauai’s Port Allen Airport.

Under the Safe Drinking Water Act, the EPA in 2005 banned large-capacity cesspools, defined as serving multi-unit residential dwellings such as townhouse complexes and apartment buildings, or 20 or more persons per day in non-residential dwellings, such as rest areas or churches.

Smoky Mountain has agreed to close the cesspool no later than April 30, 2021.

“Island water resources are vulnerable to pollution from large capacity cesspools,” said EPA Pacific Southwest Regional Administrator John Busterud in a news release. “EPA will continue our efforts to close the remaining such systems on Kauai.”

In March, the EPA also shut down a dozen large-capacity cesspools on Hawaii island run by two property owners, who were fined $144,696.

In July, the EPA fined the state and two counties for the operation of three pollution-causing cesspools at Helemano Plantation on Oahu and Kainaliu Comfort Station at Kealakekua on Hawaii island.

Since the 2005 federal ban, more than 3,600 of large-capacity cesspools in Hawaii have been closed, according to the EPA. However, many hundreds remain in operation.

Cesspools — basically underground holes used for the disposal of human waste — collect and discharge untreated raw sewage into the ground, where disease-causing pathogens and harmful chemicals can contaminate groundwater, streams and the ocean, according to the EPA.

In Hawaii, where cesspools are used more widely than in any other state, groundwater provides 95% of all domestic water.

In 2017, the state passed Act 125, which requires all cesspools to be replaced by 2050. A state income tax credit is available for upgrading qualified cesspools to a septic system or aerobic treatment unit, or connecting them to a sewer. But that tax credit ends on Dec. 31.

EPA also offers incentives for regulated entities to voluntarily self-police, disclose and close large-capacity cesspools.