Over 12 million gallons of treated wastewater that did not meet treatment facility standards was spilled into Lake Allatoona last week — days before Memorial Day weekend — the Cobb County Water System announced Tuesday.

The county’s Northwest Water Reclamation Facility, from which the two spills occurred on May 21 and 22, is operating normally but water employees are still investigating the cause, according to a news release.

The water system treated the affected water with disinfectant, and it will not impact the drinking water supply, officials said. The water quality was discovered to be below standards during routine testing this week, and more water sampling will be done upstream and down stream.