FRWA has been conducting bacteria monitoring in Connecticut and sharing data with CT DEEP since 2004. FRWA monitors a total of 42 locations for bacteria in the Farmington River Watershed in Connecticut. FRWA starting monitoring bacteria in the headwaters in Massachusetts's in 2019, at 17 sites, and we share all data with MassDEP.

To see our most current water quality data, read our 2023 Water Quality Report.

In 2002, the CT Department of Energy & Environmental Protection (CT DEEP) added a 20-mile section of the Farmington River – from the town of Farmington (where the river turns north) to Rainbow Dam in Windsor – to the state’s list of impaired water bodies because of elevated bacteria levels. Although E. coli is not considered safe in drinking water at any levels, the current standards for “non-designated swimming areas” such as in the Farmington River are 410 CFU (colony forming units) per 100 milliliter water sample. Review the fact sheet on E. coli from the Connecticut Department of Public Health.

FRWA E. coli data can be viewed on CRC's Is It Clean? website.

Who Tests for Bacteria in the River?

  • The CT DEEP conducts infrequent monitoring of bacteria in all of the rivers in the State.
  • Since the River is a popular recreational resource, the Farmington Valley Health District (FVHD) has conducted water sampling along the River for years. You can request information about their results.
  • In 2004, FRWA joined with the FVHD to monitor for bacteria in additional locations, and provide the results to the public.
  • FRWA analyzes samples for bacteria, in partnership with the Town of Simsbury Wastewater Treatment Plant.
  • FRWA monitoring sites include the Farmington River and its tributaries in Massachusetts, and the Upper and Lower River segments in Connecticut.
  • Data is shared with CT DEEP, MassDEP, and CRC's Is It Clean?

Sources of E. coli Bacteria

Most bacteria encountered in nature are harmless to humans and many are important as decomposers. They break down dead plants and animals into nutrients that are released back into the ecosystem. Bacteria as “recyclers” are vital to a healthy stream.

However, bacteria that grow in the intestines of mammals and birds and make their way to our waterways are a cause of concern. Bacteria can enter the river via storm water, catch basins, sediment, runoff, discharges, and spills. When surrounding lands are more highly developed or “urbanized,” more bacteria reach the river. Where humans or animals interface with streams, either directly or just by living nearby, there is increased likelihood that harmful bacteria will contaminate the water. It is difficult to pinpoint sources of contamination, since bacteria enter streams from:

  • Storm water runoff (may contain multiple sources of bacteria)
  • Wastewater treatment plant discharges or overflows
  • Sewer line leaks
  • Trash
  • Failing septic systems
  • Wildlife
  • Birds, especially waterfowl
  • Pet waste and farm animal waste

Is it Safe to Swim in the Farmington River?

Yes, but at your own educated risk. When the amount of bacteria in the water increases, so does the risk of getting sick from contact with the water. The most common ailment resulting from exposure to heightened bacteria levels is gastroenteritis and other intestinal discomforts. For more information, read the CT DEEP’s Water Quality Criteria.

Note that the Farmington River has no official, state “Designated Swimming” areas. Full body contact with water is what is expected at “Designated Swimming” areas, while other recreational activities have some degree of contact with the water. In reality, multitudes of people do flock to the river for recreational uses of all types, so water quality testing is done by the Farmington Valley Health District throughout the recreational use time period at established (but unofficial) swimming areas in the Farmington River Watershed. To learn more, contact us, or view our results on CRC's Is It Clean? website.


  • The most consistently high levels of bacteria in the river are recorded during and after rain events. During rain or snowmelt, bacteria levels in the River rise almost instantaneously and remain elevated for an unknown period. With no actual designated swimming areas, there can be no “Beach Closures” issued– so there is no way of knowing when it’s safe to go back in the water.  Staying out of the River for some length of time following rain is the best public health guidance we can offer.  When the turbidity (murkiness) of the water has lessened, this is some indication that bacteria levels are returning to a safe range.
  • Keep the water away from your face or open wounds. Illness may occur if one comes in contact with or ingests water with high bacteria.
  • Be aware that wastewater treatment plants disinfect effluent entering the river between May 1 and October 1. Outside that time period there is no chlorination, ultraviolet radiation, or other treatment of the effluent for bacteria, so bacteria levels can be elevated.
  • Stay out of the water when you are sick, because you may share your germs with those who would like to remain healthy.
  • Take responsibility! Keeping the river clean and safe is the job of all who enjoy it – paddlers, tubers, fishermen, hikers, picnickers, dog-walkers, cyclists, and riverfront residents. The beauty and safety of the river is best preserved when all trash and waste is properly disposed of.  If you Pack It In – Pack It Out!