Greater Cincinnati Water Works

Greater Cincinnati Water Works

Water Sources & Resource Protection


Where Does My Water Come From?

Greater Cincinnati Water Works supplies water from two sources:

  • The Miller Treatment Plant treats surface water from the Ohio River and supplies 88% of drinking water to GCWW's customers, including most of the City of Cincinnati.
  • The Bolton Treatment Plant treats groundwater from ten wells in the Great Miami Aquifer. It is located in southern Butler County. Our aquifer (buried sand and gravel filled with water) is 150-200 feet deep and 2 miles wide. Bolton Plant supplies about 12% of GCWW water.

Protecting Our Water Resources

Greater Cincinnati is fortunate to have a plentiful supply of water in both the Ohio River and the Great Miami Aquifer. The first step in providing the highest quality water to customers is to protect our source waters.


Ohio River Source Water Monitoring and ProtectionSource Water Monitoring Stations Map

GCWW monitors source water from the Ohio River by routinely testing water before it enters the treatment plant.

In addition, GCWW participates in a coordinated early warning organic detection system on the Ohio River. This system, the first of its type in the U.S.:

  • warns treatment plants downstream about spills so that measures can be taken before the spill reaches water intakes.
  • was developed by water utilities along the Ohio River in conjunction with ORSANCO (Ohio River Valley Water Sanitation Commission).
  • consists of 13 monitoring stations located along the Ohio River.

Ohio Environmental Protection Agency has classified the Ohio River as highly susceptible to contamination, as with all surface waters. This is because it is open to the environment, and pollution may spread quickly with the flow of the river.

GCWW has several barriers between potential pollution and your tap water. The first barrier, a source water protection program, is designed to prevent and monitor contamination in the river.

GCWW also has several options to protect the drinking water, ranging from turning off the intake and using stored water until pollution passes, to altering a treatment process to remove contamination. GCWW is one of only a few water treatment plants in the nation that has included granular activated carbon (GAC). GAC has been recognized as the best available technology for removing the most common chemicals found in spills in the Ohio River.


Great Miami Aquifer Source Water Protection

GCWW's Bolton Plant treats groundwater from the Great Miami Aquifer (an aquifer is buried sand and gravel filled with water) and provides water to the northwestern area of Hamilton County and parts of Warren and Butler Counties.

Ohio EPA has classified Bolton water as having a high susceptibility to contamination because the Great Miami Aquifer does not have a protective clay layer, the water is shallow, there are potential contaminant sources nearby, and there are low levels of nitrates in the aquifer. This does not mean that the aquifer is contaminated, only that it is vulnerable to contamination.

Cincinnati recognized the vulnerability of the aquifer more than a decade ago and has worked hard as a member of the Hamilton to New Baltimore Groundwater Consortium to develop an award-winning source water protection program to protect the aquifer. The Consortium's program has been recognized by the American Water Works Association as one of the best in the country.