Dayton, Ohio has something most American cities would envy: it sits directly on top of one of the largest and most productive aquifers in the United States. The Great Miami Buried Valley Aquifer supplies drinking water to over 1.5 million people across the Miami Valley region, and Dayton’s water utility draws almost exclusively from this underground source.
The aquifer is a glacial deposit — a massive underground gravel bed left behind by retreating ice sheets thousands of years ago. It can yield up to 100 million gallons per day and produces naturally filtered water that requires relatively minimal treatment. Dayton’s drinking water consistently ranks among the best-tasting in Ohio.
So what’s the problem?
Wright-Patterson Air Force Base and PFAS
The biggest threat to Dayton’s water comes from the sky — or more precisely, from the base that watches it. Wright-Patterson Air Force Base, one of the largest military installations in the country, sits on the eastern edge of the aquifer. Decades of using PFAS-containing aqueous film-forming foam (AFFF) for firefighting training have left a significant PFAS contamination plume in the groundwater.
The Department of Defense has confirmed PFAS contamination at multiple locations on and around the base. Some monitoring wells have shown PFOA and PFOS concentrations well above the EPA’s maximum contaminant level of 4 parts per trillion. The contamination has been detected in off-base private wells in Fairborn, Riverside, and portions of unincorporated Greene County.
The City of Dayton’s municipal wells are positioned upstream and at sufficient distance from the worst contamination, and the city’s treatment processes include monitoring for PFAS. But the aquifer is a connected system — contamination can migrate over time. Ohio EPA and the Air Force are conducting ongoing investigation and remediation, including providing bottled water and connecting affected private well users to municipal supply.
Legacy Industrial Contamination
Dayton was a manufacturing powerhouse through most of the 20th century — automotive parts, tool and die, chemical production, and the National Cash Register Company all operated here. Many former industrial sites have left behind volatile organic compounds (VOCs) and heavy metals in soil and groundwater.
Several Superfund and state cleanup sites in the Dayton area involve groundwater contamination. The Behr Dayton Thermal Products site and the former Chrysler Airtemp facility are among the more significant. Pump-and-treat systems and monitored natural attenuation programs are ongoing at multiple locations.
The city’s wellfield protection program works to prevent new contamination sources from threatening the aquifer’s recharge zones. It’s one of the more aggressive municipal wellhead protection programs in Ohio.
Nitrate Pressure from Agriculture
The Miami Valley is surrounded by some of Ohio’s most productive farmland. Agricultural runoff — particularly nitrates from fertilizer application — is a chronic concern for the buried valley aquifer. While the deep portions of the aquifer have some natural protection from overlying clay layers, the shallower zones are vulnerable.
Dayton’s municipal wells draw from deep enough that nitrate levels have stayed well below the EPA’s 10 mg/L maximum contaminant level. But private wells tapping shallower depths in surrounding Montgomery, Greene, and Miami counties don’t always have that protection. The Ohio EPA recommends regular nitrate testing for rural well owners in the Miami Valley.
Water Treatment and Distribution
Dayton’s water treatment is relatively light by municipal standards — a testament to the aquifer’s quality. The city uses chlorine for disinfection and adds fluoride. There’s no need for the extensive filtration that surface water systems require.
The distribution system, however, is aging. Portions of Dayton’s water mains date to the early 1900s. The city has been working on infrastructure replacement, but lead service lines remain in older neighborhoods. Dayton’s 90th percentile lead levels at the tap have historically stayed below the action level, but individual homes can vary significantly.
What Residents Can Do
- Municipal water users: Request your home’s service line material from the city. If lead, use a certified point-of-use filter while awaiting replacement.
- Private well owners: Test annually for nitrates, bacteria, and PFAS — especially if you’re within 5 miles of Wright-Patterson AFB.
- Taste or odor changes: Report them to the city. The aquifer-based supply shouldn’t have seasonal taste issues. Changes could indicate a problem.
- Know your rights: If you’re near Wright-Patterson and have PFAS contamination, the Air Force may be required to provide alternative water supply.
If you’re concerned about your water quality, a certified water treatment professional can test your water and advise on the right treatment system for your situation.
For more on Ohio water issues, see our coverage of Akron water quality. Learn more about how PFAS treatment works.
Sources: City of Dayton Water Department, Ohio EPA, US Air Force PFAS Investigation, EPA SDWIS, USGS Great Miami Buried Valley Aquifer Studies