ST. CHARLES, Mo. – Days after shutting down its water treatment plant over ammonia concerns, the City of St. Charles has reopened the plant and is once again providing drinking water to residents.

St. Charles city officials shut down the Elm Point Water Treatment Plant last weekend when its last operational well experienced “a drop in the free level of ammonia in raw water.” Free ammonia is essential because it serves as the primary disinfectant in St. Charles’ water system.

According to a news release from the City of St. Charles, the St. Louis Regional Office of the Missouri Department of Natural Resources inspected the site after some follow-up procedures and gave the City approval to resume drinking water production late Tuesday evening.

The City of St. Charles also conducted several tests to confirm the treatment plant meets Missouri safety standards, setting up a temporary chemical feed pump and dosing system at the water treatment plant.

“The City continues to take every measure possible to provide the residents of Saint Charles with safe drinking water and wants to ensure the residents that the water has and continues to be safe for use and consumption,” said the city in a news release.

When the plant shut down earlier this week, It stopped operations at the last operational well in St. Charles. The plant was producing a million gallons of drinking water per day for St. Charles residents and businesses. It provided around one-sixth of the water demand for St. Charles customers, with heavy demand during the summer.

While the plant was shut down, and even leading up to it, St. Louis City was providing water for the City of St. Charles. Amid the shutdown, city officials could not say for certain if the drop in free ammonia levels was connected to the ongoing contamination issues at Elm Point involving Ameren Missouri’s Huster Road Substation.

Ameren said in a statement Monday they did not receive and data or analysis indicating the issue was connected to the company.