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Charles River

The Charles River Initiative

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Clean Charles River Initiative

Chart: Reduction of Combined Sewer Overflow Discharges to Charles River (1988-2013)View a larger version of image.
The controls MWRA implemented resulted in a dramatic reduction of CSO discharges to the lower Charles River. Reductions went from over 1.7 billion gallons per year prior to 1988, down to approximately 20 million gallons (MG) in 2014. Discharges are projected to drop to 6.88 MG in the next few years, and over 90% of those discharges will be treated at the Cottage Farm facility. This represents an approximately 99% decrease in CSO discharges to the Lower Charles River since 1988.

In 1995, EPA launched an ambitious effort make the Charles River both fishable and swimmable. Thanks to partners in numerous federal, state and local agencies as well as nonprofit groups, private institutions and citizens, the Clean Charles River Initiative has improved water quality in the river.

Using sound science, cutting-edge technologies and strong targeted enforcement, EPA and its partners have determined the causes of pollution and poor water quality in the River.

Since 1995, municipalities and the Massachusetts Water Resources Authority (MWRA) have made remarkable strides to improve water quality by reducing illicit sewage discharges to storm drain systems and Combined Sewer Overflows (CSOs), respectively.

The municipalities of the lower Charles River (including: Boston, Cambridge , Newton, Brookline Watertown and Waltham) have reduced sewage-contaminated stormwater flows through illicit storm drain connections. That effort has eliminated in excess of 48,000 gallons of sewage contaminated stormwater flowing into the River per day since 2004. This is in addition to the more than one million gallons per day of sewage contaminated stormwater that has been eliminated from municipal storm drain systems from Watertown to Boston harbor, an effort that began with the launch of the Charles cleanup effort in 1995.

Sewage discharges from CSOs to the river declined significantly as a result of the 2005 settlement between EPA and the MWRA. As a result of various CSO projects throughout the lower Charles (in many cases, eliminating CSOs entirely, MWRA has reduced CSO discharges by an impressive 99.5%).

We have made significant progress targeting bacterial sources of pollution in The River. But, there continue to be problems with excessive amounts of nutrients entering the river, especially phosphorus. See the Environmental Challenges for updated overview of these latest challenges.

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Sound Science on the Charles River

The improvements in water quality on the Charles River are a direct result of sound science. EPA, U.S. Department of Interior Exit, U.S. Geological Survey Exit, Mass DEP Exit, Charles River Watershed Association Exit, Rocky Mountain Institute Exitand New England Interstate Water Pollution Control Commission Exithave conducted studies and produced reports analyzing the River.

Please see Reports and Links for a more complete view of reports on the Charles River.


Today we have a river that is safe for recreational boating virtually all of the time, and safe for swimming 70% of the time. It is a river that is now a resource for an active wind surfing community, an annual swim race and catch and release fishing. Indeed, we are much closer to the original goals of making the Charles both fishable and swimmable.

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Charles River Watershed Report Cards

Swimmers on the Charles RiverSwimmers on the Charles RiverEPA has been assigning a report card grade for the lower Charles River since calendar year 1995. Beginning in 2019, grades are assigned to six individual water body segments including two tributaries. Prior to 2019, a single grade was assigned to just the lower Charles River. EPA uses the Charles River Report Card to measure and evaluate progress towards meeting the State of Massachusetts bacterial water quality standards for swimming and boating as well as to assess general health of the watershed.

Grading Criteria 2019

Starting with 2019, the Charles River Watershed Association (CRWA), in coordination with EPA, will begin using an assessment method that encompasses all 80 miles of the mainstem river as well as two tributaries to provide the public with a more accurate assessment of local water quality conditions and greater transparency for all stakeholders. The report card will be based on E. coli data from thirty-nine sampling sites, collected monthly by CRWA volunteers. While the new grading system continues to measure the percentage of time water quality samples meet bacterial swimming and boating standards, it also incorporates cyanobacteria (toxic blue-green algae) blooms and combined sewer overflows (CSOs), which are both public health hazards, especially for boaters and anyone who comes into contact with the water. The Charles will now receive grades for six waterbody segments: the Upper Watershed (Hopkinton to Medfield), the Upper Middle Watershed (Sherborn to Dedham), the Lower Middle Watershed (Newton to Waltham), the Lower Basin (Watertown to Boston), the Stop River, and the Muddy River.

Bar chart: 2019 Charles River Report Card Grades

Charles River Watershed Water Quality Grades and Compliance Rates
  Overall E. coli* Other criteria**
Site Grade Total Grade Total Cyanobacteria Combined Sewer Overflow
Upper Watershed A- 86.5% A- 86.5% 0.0% 0.0%
Stop River A- 86.3% A- 86.3% 0.0% 0.0%
Upper Middle Watershed A 94.1% A 94.1% 0.0% 0.0%
Lower Middle Watershed A 90.7% A 90.7% 0.0% 0.0%
Lower Basin B 75.5% B 78.7% 1.3% 1.9%
Muddy River D- 41.3% D- 41.3% 0.0% 0.0%

*Figures represent average percentage of time that state bacterial standards are met.

**Figures represent percentage of time that each waterbody stretch is affected by a cyanobacterial bloom or combined sewer overflow.

For more information on how the grades are calculated please read the Frequently Asked Questions, review the report card map, and the data on CRWA's website.

Grading Criteria Prior to 2019

When assessing water quality to assign a grade to the lower Charles River prior to 2019, EPA used a comparison with previous years and general trends, as well as qualitative criteria, as follows:

A - met swimming and boating standards nearly all of the time
B - met swimming and boating standards most of the time
C - met swimming standards some of the time, and boating standards most of the time
D - met swimming and boating standards some of the time
F - fail swimming and boating standards most of the time

Lower Charles River Report Cards 1995-2018
Year Overall Grade % Meets Standards % Meets Standards in Dry Weather Conditions % Meets Standards in Wet Weather Conditions
  Boating Swimming Boating Swimming Boating Swimming
2018 B 92 53 94 66 91 47
2017 A- 95 72 96 89 95 64
2016 B 86 55 98 61 80 53
2015 B+ 95 69 98 86 93 60
2014 B+ 91 65 100 86 86 53
2013 A- 96 70 97 84 95 63
2012 B+ 87 67 99 93 81 53
2011 B 82 54 96 89 74 35
2010 B+ 86 66 94 86 82 54
2009 B+ 93 62 92 69 94 58
2008 B+ 95 48 91 58 92 42
2007 B++ 100 63 100 84 100 50
2006 B+ 90 62 100 80 84 51
2005 B+ 97 50 97 59 96 32
2004 B+ 96 54 94 68 97 62
2003 B- 85 46 91 56 81 41
2002 B 91 39 100 71 86 21
2001 B 82 54 97 80 74 40
2000 B 92 59 94 82 91 46
1999 B- 90 65 100 71 85 62
1998 C+ 83 51 98 85 74 31
1997 C 70 34 87 56 61 22
1996 C- 57 21 94 40 45 15
1995 D 39 19        

The grade is based on a comparison with previous years and general trends. Given that the grades are based on a limited set of data, some annual fluctuations depending on weather are expected. Figures represent the percentage of time that state bacterial standards are met.

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Charles River in the News

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