- Wellfield Information
- City Drinking Water Well CW-9 Update
City Drinking Water Well CW-9 Update
The City of St. Charles voluntarily began weekly water sampling and analysis of the influent and effluent at the Elm Point drinking water treatment plant in November 2022. The influent is untreated groundwater from the wellfield coming into the treatment plant. The effluent is treated water leaving the plant for the residents and businesses to use and drink. The City was forced to start routine monitoring of the water entering and leaving the treatment plant, after repeated requests to require Ameren Missouri and the other responsible parties to perform this sampling were ignored by the USEPA and Missouri DNR. This was despite growing evidence of spreading contamination across the Elm Point Wellfield and detections of contaminants in the City’s drinking water wells.
Samples collected on November 15, 2022 indicated that vinyl chloride was detected within the water entering the treatment plant, but not in the water leaving the treatment plant that is used as drinking water by the City’s residents and businesses. The concentration of vinyl chloride in the influent was measured below the maximum contaminant level (MCL) which is the level considered safe to drink by the USEPA and Missouri DNR. Laboratory analytical results for the groundwater sample collected from City drinking water well CW-9 on November 18, 2022 also indicated the presence of vinyl chloride and confirmed to be the source of the contaminants detected in the water entering the treatment plant. The concentration of vinyl chloride in groundwater collected from drinking water well CW-9 was also less than the USEPA MCL.
Upon receiving the laboratory results on December 2, 2022 from the sampling of well CW-9 performed on November 18, 2022, the City of St. Charles immediately suspended operation of drinking water well CW-9. As a result, the City is only operating two out of the City’s seven drinking water wells which includes wells CW-7 and CW-10. Laboratory analytical results have shown that that hazardous chemicals are not present in groundwater samples collected from these two drinking water wells.
The City of St. Charles elected to voluntarily shutdown drinking water well CW-9 so that chemicals would not continue to migrate towards the well at increasing concentrations and to ensure that water remained safe for the City’s citizens to drink and use. The continued operation of this well could have resulted in increasing concentrations of vinyl chloride and other hazardous chemicals in the water entering the Elm Point treatment plant. It is the City’s belief that despite opposing recommendations from the USEPA, Missouri DNR, Ameren Missouri, and others, that the safest option was to simply shut off drinking water well CW-9, as was previously done to drinking water wells CW-6 and CW-8, to ensure the continued protection of the City’s residents and businesses. The City understands that this means that it will have to purchase more water from the City of St. Louis to meet current demands and in the long term could lead to the potential shortage of drinking water during high peak demand in the summer months.
In response to the deteriorating conditions caused by the migration of hazardous chemicals from the Ameren Huster Road Substation towards the drinking water wells, the City again requested on December 2, 2022 that the USEPA and Missouri DNR require Ameren Missouri and the other responsible parties to: (1) upgrade the Elm Point drinking water treatment plant to remove hazardous chemicals and allow the City to operate all of their drinking water wells without the risk of contaminated water being distributed to its citizens, and (2) relocate the City of St. Charles wellfield to an area free of contamination.
While awaiting a response to these requests, the City continues to sample the influent and effluent within the Elm Point drinking water treatment plant at least once each week and routinely analyze samples collected from each of the City’s operating and suspended drinking water wells.