The federal court settlement over penalties for releasing partially treated wastewater into injection wells from the Lahaina Wastewater Reclamation Facility could cost Maui taxpayers an additional $1 million.

Maui County has conditionally agreed to pay $971,814 in attorneys’ fees and other costs in connection with federal Clean Water Act violation claims four community groups brought against the county, according to court documents filed Dec. 29 in U.S. District Court in Honolulu.

The groups are Hawaii Wildlife Fund, Sierra Club-Maui Group, Surfrider Foundation and West Maui Preservation Association. Earthjustice lawyers represented them in their federal lawsuit against the county.

In September, Maui County agreed in a conditional settlement to spend $2.5 million on projects to divert treated wastewater from the Lahaina facility and to pay a $100,000 penalty to the federal government.

The agreements are conditional because the county is appealing federal court rulings that found discharges of treated wastewater from the Lahaina facility without a pollutant discharge permit violate federal clean-water laws and that the county was liable for civil penalties.

The county maintains that state and federal safe-drinking-water laws allow it to inject treated wastewater into underground wells that connect to groundwater that eventually enters the ocean. It will execute the settlement and pay the attorneys’ fees only if it loses its appeals.

While the appeals are pending, the county has agreed to apply for and abide by a federal pollutant discharge permit to continue to discharge wastewater into underground wells at the Lahaina facility.

The four community groups sued Maui County in 2012 because they claim that treated wastewater from the underground wells is responsible for killing the coral reef and triggering outbreaks of invasive algae in nearshore waters off Kahekili Beach.