Tompkins County, New York: drinking water report. Tompkins County in central New York has a population of about 105,000, centered on Ithaca and Cornell…
Tompkins County in central New York has a population of about 105,000, centered on Ithaca and Cornell University. The Bolton Point Water System draws from Cayuga Lake – one of the Finger Lakes – while the Ithaca Water Works draws from Six Mile Creek. The county's steep gorges and thin soil layers over fractured shale create conditions where surface contamination can reach groundwater quickly.
Cayuga Lake has faced harmful algal bloom events in recent years. According to the New York State DEC's 2024 HAB monitoring report, cyanobacteria blooms were documented in the southern end of Cayuga Lake near the Bolton Point intake during late summer. Microcystin toxin was detected at low levels, and the treatment system's activated carbon and ozone processes addressed it, but bloom frequency has been increasing as nutrient loading from agricultural runoff rises.
The EPA's UCMR5 data shows PFAS at low levels in the Bolton Point system. The former Tompkins County Airport has confirmed AFFF use. A 2024 NYSDOH report documented PFAS in one system in the county above the state MCL of 10 ppt. Naturally occurring methane in some of the county's groundwater wells is also a concern – not for drinking water safety but for explosion risk in confined spaces.
Late summer algal bloom season is when Cayuga Lake source water faces the most stress. The treatment systems monitor for toxins, but household filtration adds a margin of safety during bloom events.
Check your water for current data on your system. For algal toxins, activated carbon filters are effective. For PFAS, reverse osmosis adds broader protection. Our water filter guide covers systems for lake-sourced water. Pull your detailed report for seasonal data, and visit our New York page for statewide context.
Drinking water is one exposure route. These federal datasets also cover Tompkins County, NY.
The EPA places Tompkins County, NY in Zone 1 - the EPA's highest-risk category, where the predicted average indoor radon level is above 4 pCi/L. Zone maps predict an area's radon potential from geology and existing indoor readings; they say nothing about a specific house. Testing is the only way to know your own level.
57% of homes in Tompkins County, NY were built before 1980, and 27% before 1950. Residential lead paint was banned in 1978, so housing age is the strongest available proxy for lead-paint exposure. This describes the county's housing stock, not any one home.
Modelled annual fine-particle pollution (PM2.5) in Tompkins County, NY averages 6.2 µg/m³, within the EPA's annual standard of 9 µg/m³. These are CDC modelled county estimates rather than readings from a specific monitor.
How radon zones work · Air quality by county · Lead exposure guide