Water Treatment Plant

The citizens of St. Marys are very fortunate that our four wells are capable of providing large quantities of water, free of bacteria and other contaminants. Two of the wells are located in a gravel formation in the ancient Teays River Valley System, while the other two are located in a limestone formation. Wells Number 1 and Number 2 are limestone wells in the Carl Jackson Well Field. Both are 270 feet deep and pump 1100 gallons per minute. Wells Number 4 and Number 5 are gravel wells in the Barrington Well Field. Well Number 4 is 320 feet deep and pumps 850 gallons per minute and well Number 5 is 354 feet deep and pumps 1200 gallons per minute.

Untreated well water pumped into the treatment plant goes through a complex, multi-stage treatment process that takes about 12 hours, producing a consistent supply of high quality drinking water. The treatment plant is a lime-soda ash softening facility; softening the water makes it 'kinder' to appliances, machinery, and the human body.

Water Treatment Stages

  • Rapid Mixers: treatment chemicals (lime, soda ash, and ferric chloride) thoroughly and violently mix with well water.
  • Flocculation: gentle mixing allows treatment chemicals to react with hardness causing substances in the water, forming heavy particles that will settle out of the water.
  • Sedimentation: heavy particles separate from the water by gravity. The sludge that settles out is pumped to one of three storage lagoons where it thickens. The clear water that is left after the thickening discharges to a small creek. After several years, contractors apply the sludge, which is valuable soil conditioner, to agricultural land.
  • Stabilization: liquid carbon dioxide is added to control the pH of the treated water, stabilizing it in the process.
  • Chlorination: a small amount of chlorine is added to provide protection from accidental cross-contamination once the water leaves the treatment plant. Ohio EPA requires that a chlorine residual must be present in the water throughout the system.
  • Filtration: rapid sand filters remove any remaining fine particles producing clear, softened, safe drinking water.
  • Storage and delivery: an underground tank called a clearwell holds treated water until it is needed for consumption. High pressure pumps deliver the water to consumers. Two water towers with a combined capacity of 1,250,000 gallons, store water on the system, controlling water pressure and providing fire protection.


The Water Treatment Plant Laboratory is Ohio EPA approved and contains all the various equipment needed to monitor the water. Lab Technicians, thoroughly trained and certified by Ohio EPA to do both chemical and bacteriological tests, check water quality at all stages of the treatment process to insure that the water is treated properly. Tests include pH, hardness, alkalinity, chlorine residual, and bacteriological. In addition to routine tests, we monitor for the presence of more than 130 complex chemical compounds. This monitoring, mandated by EPA and the Safe Drinking Water Act (SDWA), helps protect the health of the public.

On this page you will find a copy of the annual water quality report that is distributed to all consumers served by the City of St. Marys and also a complete list of the more than 130 contaminants that are monitored by the City of St. Marys. View the 2022 Drinking Water Quality Report (PDF). View the 2022 Detailed Monitoring Report (PDF).


Regular maintenance is a very important part of operating a public water supply. Personnel are charged with many tasks and projects in order to keep the treatment plant operating at peak levels. Examples include: preventative maintenance of treatment plant equipment, regular inspections of the wells and water towers, and many other activities.


Four full time operators staff the St. Marys Water Treatment Plant sixteen hours per day, seven days per week. One laboratory technician and two maintenance men split time between the plant and other duties. All employees are Ohio EPA certified operators. The increasingly technical nature of Federal and State regulations requires continuing training on the part of all employees.