Charles River Report Card
Project Overview
EPA has used the Charles River Report Card to measure and evaluate progress towards meeting the State of Massachusetts bacterial water quality standards for swimming and boating since 1995. In 2019, the grading system was updated to include grades for the entire length of the Charles River, and has added cyanobacteria and combined sewer overflows (CSOs) as additional health indicators. It uses sound science to report on the recreational health of the river and educate the public on challenges the Charles River faces.
2019: Charles River Receives A to D- With New Grading System
In coordination with the Charles River Watershed Association (CRWA), U.S. EPA has developed a new grading system that for the first time is reporting on the entire length of the Charles River, and is also taking more pollutants into account.
Since 1995, U.S. EPA has graded the Lower Charles River Basin—Watertown to Boston—using only E. coli data from water samples collected monthly by CRWA volunteers. Starting this year, the grade encompasses all 80 miles of the river and two tributaries, based on data from thirty-nine sampling sites. Grades are being issued for four sections of the Charles River mainstem: the Upper Watershed (Hopkinton to Medfield), the Upper Middle Watershed (Sherborn to Dedham), the Lower Middle Watershed (Newton to Waltham), and the Lower Basin (Watertown to Boston). Two tributaries of the Charles have also been graded: the Stop River in Medfield, and the Muddy River in Boston.
Since 1995, U.S. EPA has graded the Lower Charles River Basin—Watertown to Boston—using only E. coli data from water samples collected monthly by CRWA volunteers. Starting this year, the grade encompasses all 80 miles of the river and two tributaries, based on data from thirty-nine sampling sites. Grades are being issued for four sections of the Charles River mainstem: the Upper Watershed (Hopkinton to Medfield), the Upper Middle Watershed (Sherborn to Dedham), the Lower Middle Watershed (Newton to Waltham), and the Lower Basin (Watertown to Boston). Two tributaries of the Charles have also been graded: the Stop River in Medfield, and the Muddy River in Boston.
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The new grading system demonstrates the variability in water quality in different stretches of the river. Based on 2019 data, grades range from an “A” in the middle reaches of the Charles River (Sherborn to Waltham) to a “D-” in the Muddy River, a tributary in Boston and Brookline. The Upper Watershed received an “A-”. The Lower Basin of the Charles River, the popular reach between Watertown and Boston, received a “B”—remaining steady from the 2018 grade.
Also new this year, in addition to E. coli bacteria, the river is also being graded on 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. Read the full press release.
Also new this year, in addition to E. coli bacteria, the river is also being graded on 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. Read the full press release.
FAQs
Why is a new grading system being used?
One of the primary reasons for changing the grading system is that when the system began in 1995, it only evaluated the Lower Basin of the Charles River, from Watertown to Boston. However, Charles River Watershed Association (CRWA) collects monthly samples along all 80 miles of the river, and this data can be utilized to evaluate the health of the entire Charles River, in order to better understand what may affect the health in different portions of the river. CRWA also collects regular samples on two tributaries of the river, the Stop River in Medfield and the Muddy River in Boston; the health of those tributaries can additionally be evaluated. Grading the watershed by segments provides the public a more accurate assessment of local water quality conditions and greater transparency for all stakeholders. It also allows CRWA and regulatory agencies to focus efforts where they are most needed to bring about a positive change.
The previous grading system was also significantly influenced by the amount of precipitation in a given year. As E. coli bacteria counts are highest after rainfall events, the number of rainfall events that were sampled was found to influence the report card grade, so that it reflected the weather and not a long-term trend, as it is intended. The new grading system makes the grade calculation more consistent and uses a three-year rolling average of E. coli counts to smooth out the effect of differences in weather from year to year.
Finally, the new grading system takes into account advisories due to Combined Sewer Overflows (CSOs) and cyanobacteria (blue-green algae) blooms, which both have negative health effects on humans using the river for recreation. While the primary calculation of the grade is from E. coli bacteria sample results, CSOs and cyanobacteria bloom advisories are taken into account to spread awareness of these additional contaminants.
The previous grading system was also significantly influenced by the amount of precipitation in a given year. As E. coli bacteria counts are highest after rainfall events, the number of rainfall events that were sampled was found to influence the report card grade, so that it reflected the weather and not a long-term trend, as it is intended. The new grading system makes the grade calculation more consistent and uses a three-year rolling average of E. coli counts to smooth out the effect of differences in weather from year to year.
Finally, the new grading system takes into account advisories due to Combined Sewer Overflows (CSOs) and cyanobacteria (blue-green algae) blooms, which both have negative health effects on humans using the river for recreation. While the primary calculation of the grade is from E. coli bacteria sample results, CSOs and cyanobacteria bloom advisories are taken into account to spread awareness of these additional contaminants.
what are the grades for the 2019 calendar year?
The grades for the 2019 calendar year range from “A”s in the Middle portions of the Watershed (Sherborn to Waltham) to a “D-” in the Muddy River tributary. The Lower Basin of the Charles River (Watertown to Boston) received a “B” grade, which is comparable to previous years using the previous grading method.
what data are the grades based upon?
The Charles River Watershed Annual Report Card grades are based on water quality data provided by CRWA’s volunteer monthly monitoring program. Each month, a group of trained CRWA volunteers gather water quality samples from 35 representative sites throughout the watershed. These samples are sent to the MWRA laboratory at Deer Island, where they are analyzed for bacteria, nutrients, and other valuable indicators. CRWA staff assess the data for quality assurance in accordance with an EPA and MassDEP approved Quality Assurance Project Plan (QAPP). The E. coli portion of the annual grade is a measure of how frequently bacteria levels in these samples meet the state water quality standards for boating and swimming. The Commonwealth of Massachusetts has standards of 235 and 1260 E. coli per 100 mL of water as levels that should not be exceeded for safe swimming and boating conditions, respectively.
The combined sewer overflow (CSO) data is based on the number of days that CSO advisories were in effect in the relevant river segment. The CSO data compiled was from the reports produced by MWRA and the City of Cambridge, documenting overflow events. When a CSO occurs, an advisory is in place for 48 hours after the discharge. The cyanobacteria data is based on the number of days that a cyanobacteria bloom advisory was recommended by MassDPH in a given river section.
The combined sewer overflow (CSO) data is based on the number of days that CSO advisories were in effect in the relevant river segment. The CSO data compiled was from the reports produced by MWRA and the City of Cambridge, documenting overflow events. When a CSO occurs, an advisory is in place for 48 hours after the discharge. The cyanobacteria data is based on the number of days that a cyanobacteria bloom advisory was recommended by MassDPH in a given river section.
HOW ARE THE GRADES CALCULATED?
The grades are calculated based on the percentage of days during dry and wet weather that bacteria levels at each of the 39 sampling sites meet Massachusetts water quality standards for swimming and boating. An average between the overall percentages that water quality met criteria for swimming and boating for each location is calculated. The current year's percentage is averaged with the prior two years to produce the "rolling" three-year average. If a sample site was affected by a CSO and/or cyanobacteria advisory, the percentage of days over the three-year period affected by an advisory is subtracted from the E. coli percentage.
The final percentage is then compared to the scale below and the appropriate grade assigned:
The final percentage is then compared to the scale below and the appropriate grade assigned:
GRADE |
PERCENTAGE |
A+ |
95% to 100% |
A |
90% to 95% |
A- |
85% to 90% |
B+ |
80% to 85% |
B |
75% to 80% |
B- |
70% to 75% |
C+ |
65% to 70% |
C |
60% to 65% |
C- |
55% to 60% |
D+ |
50% to 55% |
D |
45% to 50% |
D- |
40% to 45% |
F |
Less than 40% |
IF IT RAINS A LOT WILL THE GRADE BE WORSE?
Because CRWA samples are collected on set days regardless of the weather, we cannot predict how many samples will be taken in dry or wet weather each year. To calculate the grade, EPA normalizes the data to control for wet weather by giving dry weather sample results more weight in the overall grade (75% dry weather/25% wet weather). These percentages were found to be representative of a typical year of weather in Boston, and by normalizing in this way we are able to standardize the grade for year-to-year comparison. It is true that the water quality is impaired more frequently during wet weather conditions than dry conditions. If our calculations did not control for the frequency of wet and dry weather, we would see greater variability in the grade on a yearly basis that would mask longer-term trends in water quality. In addition, the use of a 3-year rolling average is specifically designed to better address climate variability from year to year, while allowing for long-term data trends to be more easily discerned.
WHAT EFFECT DOES THE "ROLLING AVERAGE" HAVE ON THE GRADE?
A "rolling" average is frequently used with data sets that vary from measurement to measurement. The use of the 3-year rolling average limits the effect that a very good or very bad year can have on the overall data trend, and thus prevents the grade from varying significantly from year to year, while at the same time allowing long-term trends in the data to be more readily apparent.
WHY DO YOU INCLUDE CSO AND CYANOBACTERIA DATA IN THE GRADE?
The Charles River Report Card grade was developed to easily communicate how frequently water quality meets criteria that are acceptable for recreation (e.g. swimming and boating). There has been a lot of research done to identify a relationship between high bacteria levels and public health risk of illness during recreation in contaminated waters, which is why E. coli levels are the basis of the grade. CSOs present further risks to recreational activity, as harmful contaminants such as pharmaceuticals, PFAS, and heavy metals may be present in CSO discharges in addition to bacteria.
Cyanobacteria (blue-green algae), when highly concentrated during blooms, is known to have negative human health effects that range from skin irritation to neurological deterioration. Though specific water quality standards have not yet been developed for cyanobacteria exposure, MassDPH issues a recreation advisory when levels exceed 70,000 cells/mL.
While other parameters are important for the health of the Charles River ecosystem (e.g. nutrients, total suspended solids) they are not as easily correlated with human health. Therefore, the Charles River grade provides a snapshot of one aspect of water quality: recreation.
Cyanobacteria (blue-green algae), when highly concentrated during blooms, is known to have negative human health effects that range from skin irritation to neurological deterioration. Though specific water quality standards have not yet been developed for cyanobacteria exposure, MassDPH issues a recreation advisory when levels exceed 70,000 cells/mL.
While other parameters are important for the health of the Charles River ecosystem (e.g. nutrients, total suspended solids) they are not as easily correlated with human health. Therefore, the Charles River grade provides a snapshot of one aspect of water quality: recreation.
WHY DO SOME SECTIONS OF THE CHARLES RIVER HAVE BETTER GRADES THAN OTHERS?
The water quality at any location in a river system depends on factors in the entire area upstream of that point, including any streams, ponds, and wetlands, that may drain to that point: the point’s watershed. In the Charles River, water quality mainly varies due to the land use and stormwater infrastructure in the watershed.
Water quality in the middle reaches of the Charles River (Sherborn to Waltham) is quite good. A major reason for this is the significant areas of forests and wetlands surrounding this part of the Charles and its tributaries. The plants and soils in these natural spaces act as filters, cleaning the water of pollutants and keeping the ambient river water clean. As wetlands and forests are replaced by denser housing and road systems in the Boston area, water quality in the Lower Basin of the Charles is degraded. In these more urbanized areas, rain washes pollutants from roads and buildings into storm drains that lead directly to the Charles, without the chance for the water to be cleaned by natural filters like soil and plants. This effect is especially apparent in the Muddy River, a tributary of the Charles River in Boston, which received a “D-” grade in 2019.
Water quality in the Upper Watershed is slightly degraded compared to the Middle reaches of the Charles, due to a combination of factors. First, the area along the I-495 corridor is experiencing rapid development, increasing the amount of roads and buildings and decreasing the forest cover. Second, the Charles River has relatively low amounts of water running through it at this point. Less water in the river means that the pollution that is there is more concentrated, which is reflected in the sample results and grade.
Water quality in the middle reaches of the Charles River (Sherborn to Waltham) is quite good. A major reason for this is the significant areas of forests and wetlands surrounding this part of the Charles and its tributaries. The plants and soils in these natural spaces act as filters, cleaning the water of pollutants and keeping the ambient river water clean. As wetlands and forests are replaced by denser housing and road systems in the Boston area, water quality in the Lower Basin of the Charles is degraded. In these more urbanized areas, rain washes pollutants from roads and buildings into storm drains that lead directly to the Charles, without the chance for the water to be cleaned by natural filters like soil and plants. This effect is especially apparent in the Muddy River, a tributary of the Charles River in Boston, which received a “D-” grade in 2019.
Water quality in the Upper Watershed is slightly degraded compared to the Middle reaches of the Charles, due to a combination of factors. First, the area along the I-495 corridor is experiencing rapid development, increasing the amount of roads and buildings and decreasing the forest cover. Second, the Charles River has relatively low amounts of water running through it at this point. Less water in the river means that the pollution that is there is more concentrated, which is reflected in the sample results and grade.
WHAT IS BEING DONE TO IMPROVE WATER QUALITY IN THE CHARLES RIVER WATERSHED?
Municipalities throughout the watershed are examining their stormwater systems and related discharges for areas to make improvements. These communities are working to upgrade aging infrastructure and reduce the flow of sewage and stormwater into surface water bodies. EPA recently re-issued the stormwater general permit that applies to many municipalities throughout Massachusetts, including all of the communities within the Charles River watershed. This general permit will make a significant improvement in how stormwater is handled and discharged to receiving waters, and is designed to make significant improvements in water quality throughout the state.
CRWA works closely with all 35 municipalities in the Charles River watershed on these issues by promoting incorporation of green stormwater infrastructure into urban design. These systems, such as rain gardens and bioswales, mimic the abilities of natural wetlands and filter pollution out of stormwater before it enters rivers and streams.
CRWA works closely with all 35 municipalities in the Charles River watershed on these issues by promoting incorporation of green stormwater infrastructure into urban design. These systems, such as rain gardens and bioswales, mimic the abilities of natural wetlands and filter pollution out of stormwater before it enters rivers and streams.
WHAT IS THE DIFFERENCE BETWEEN THE CHARES RIVER AND THE MYSTIC RIVER REPORT CARD GRADES?
The new Charles River Report Card grading system is similar to the Mystic River’s report card grading system. Both systems use the same methods to calculate the E. coli portion of the grades, but the Charles River grades additionally include data from combined sewer overflows (CSOs) and cyanobacteria blooms. Another difference is due to the geometry of the river systems, as the Charles has a long main stem with smaller tributaries, and the Mystic River has larger tributaries that coalesce to a shorter main stem. In addition, the Charles River system is entirely fresh water, bounded at its end by the New Charles River Dam, whereas tidal flow enters the Mystic River below the Amelia Earhart Dam. Massachusetts’ standards for bacterial pollution are different for fresh and saltwater, so there is a slight difference in the grade calculation in the saltwater reaches of the Mystic. For these reasons, it is important to note that the grades should not be directly compared against one another. However, these grades do provide a basis to track annual progress and water quality within each watershed.