BANGOR, Maine (AP) A Maine waste facility accidentally dumped about 6,500 gallons of bleach into the local sewage system, which is a violation of its environmental permits.

The Bangor Daily News reports the disinfectant from Coastal Resources of Maine traveled to Bangor’s wastewater treatment plant and killed off some of the microorganisms used there to treat sewer water before it is released into the Penobscot River.

A Bangor water quality official says the bleach didn’t affect the ability of the plant to clean wastewater. It did, however, require staff to spend hours ensuring the integrity of its system.

The city says the waste facility also violated a prompt notification rule.

Coastal Resources, fined $4,390, has replaced a faulty valve in its cleaning systems that it said caused the bleach to be discharged.