Connecticut River E. coli Report (2019-2023)
Bacteria
E. coli
Mainstem
2019
2020
2021
2022
2023
Recreation
Human Health
Volunteers for the Connecticut River Conservancy (CRC) collect samples of the Connecticut River weekly from thirteen locations in Massachusetts and eight in Connecticut. Volunteers from the Putney Rowing Club also collect samples six times a year from one location in Vermont. Sampling usually occurs during the peak recreation season from the first week of June through sometime in September. The sampling season in 2020 was delayed until July and ran through the end of October due to the COVID-19 pandemic.
These sites were all selected as points of recreational interest; they are samples from boat ramps, docks, or at popular swimming holes. Most of the sites are directly on the mainstem of the Connecticut River. The Oxbow and Wethersfield Cove sites are located in semi-separate bodies of water that represent a mix of the main tributary to that body and the Connecticut River.
Sample results are classified as having been sampled after either wet or dry weather. A sample is classified as wet weather if more than 0.1 inch of rain has fallen in the previous 48 hours. This indicates whether a sample result is being influenced by the presence of runoff. Runoff is rainwater or snowmelt that enters directly into the nearest body of water without being filtered through groundwater systems. The more impervious surfaces like asphalt and concrete there are in a given location, the more runoff is created there during a rain event. Runoff carries with it pollutants, including bacteria, from the land into the receiving water with it.
Throughout the season, results are uploaded to Is It Clean?/¿Está Limpio? as they become available alongside other results from throughout the Connecticut River watershed.
Why E. coli?
Escherichia coli is a coliform bacteria found in the guts of all warm-blooded animals (including mammals, birds, and humans) that is excreted when they poop. Not all E. coli is pathogenic (illness causing), but some strains can be extremely harmful. It is used an indicator organism for fecal contamination of rivers and lakes. Because it is found in the gut, abundant E. coli numbers in water mean there is a higher likelihood that the water is contaminated with human or animal waste and that there is an increased risk of waterborne illness. This could be from one of the harmful strains of E. coli or other pathogenic organisms that are often found in human or animal waste but are much more difficult or costly to test for.
The Environmental Protection Agency (EPA) has made water quality recommendations for levels of E. coli to determine suitability for recreation. These are broken down into primary and secondary contact recreation. Primary contact means there is a high likelihood of accidentally ingesting water due to being fully immersed in the water such as during swimming, water skiing, or surfing. Secondary contact means there is a lower likelihood of accidentally swallowing water due to water spray or brief unintended immersion such as boating, fishing, or wading. In this report and throughout CRC’s sharing of bacteria data, “swimming” is shorthand for primary contact and “boating” is shorthand for secondary contact.
Results
Interactive Graphic
The graphic below is interactive. Hover your mouse over a point (or click if using a touch screen) on the chart to highlight its counterpart on the map.
The average of all results from the last five years on the Connecticut River have been pretty good. All sites were suitable for all types of recreation during dry weather, and most were on average suitable during wet weather as well. The few sites that were not suitable for swimming were still suitable for boating.
The Connecticut River is a large river and carries a lot of water compared to its tributaries. Because of this, runoff is easily diluted and results in generally lower bacteria numbers for the length sampled. The cluster of three sites with the highest numbers in southern Massachusetts (Medina St, Pioneer Valley Riverfront Club, and Pioneer Valley Yacht Club) are all impacted by combined sewer overflows in addition to increased runoff from urbanization. As mentioned above, Wethersfield Cove is a semi-separate body of water from the mainstem and so is more easily affected by local runoff.
How often is the river swimmable and boatable?
Each brick on the chart above represents one sample collected and is colored by which standards it is or isn’t meeting. This shows the difference between the numbers of wet and dry weather samples collected each year as well as how the weather affects the sample results. Overall, most of the samples collected meet the standard for swimming and boating in either wet or dry weather, and a majority of the samples that are either boatable only or unsuitable for recreation were collected during wet weather.
Results by Sample Date and Location
Interactive Graphic
The charts below are interactive. Select a sampling year from the tabs and hover your mouse over a column (or click if using a touch screen) to see the date, the result, and to highlight other results from the same sampling day.
The sites are ordered on the chart from upstream to downstream from top left to bottom right. Sites that were not sampled in a year do not appear on the chart.
Conclusion
Reviewing five years of E. coli data collected from the Connecticut River shows that after dry weather, the Connecticut River is usually swimmable and boatable. Even after wet weather, many sites tend to maintain their good water quality. Working to improve stormwater infrastructure and remove CSOs will continue to improve the water quality in the Connecticut River.
Complete Results
Please use the table below to browse the complete results used in this report. Fields can be filtered to find specific locations or dates.
Complete Mainstem Sampling Results
(2019-2023)