Annual Report Card Shows Water Quality Improvements in Parts of the Mystic River Watershed


BOSTON –- (RealEstateRama) — Each year, the US Environmental Protection Agency (EPA), in collaboration with the Mystic River Watershed Association (MyRWA), issues a Water Quality Report Card on water quality in the Mystic River watershed. Since 2015, EPA has utilized an enhanced, locally-specific analysis of water quality in the watershed that gives grades for 14 river segments or tributaries.


The report card grades are based on bacterial contamination found in analyzed samples that were collected by MyRWA volunteers over the past year at fifteen monitoring sites throughout the entire watershed, as well as data collected at numerous locations by the Massachusetts Water Resources Authority (MWRA).

Grade Water Segment Avg. Meeting MA water quality standards boating & swimming
Mystic River Watershed Water Quality Grades and Compliance Rates – Calendar Year 2016
A+ Upper Mystic Lake 98.9%
A Chelsea Creek 91.2%
A- Mystic River (Salt Water) 87.6%
A- Mystic River (Fresh Water) 85.8%
A- Belle Isle Inlet 85.7%
C+ Meetinghouse Brook 66.5%
C+ Malden River 65.1%
C Aberjona River 61.8%
D+ Alewife Brook 54.2%
D+ Mill Brook 53.1%
D Little River 49.4%
D- Winn’s Brook 42.0%
F Island End River 36.3%
F Mill Creek 33.5%

For the third year in a row, analysis of the data shows that water quality in the main stem of the Mystic River, including the Upper and Lower Mystic Lakes, is very good on a regular basis and meets water quality standards nearly all of the time, especially in dry weather. However, water quality in many of the tributary streams feeding the Mystic is poor, and these areas often do not meet water quality standards. Water quality is frequently poor due to bacterial contamination in tributary streams such as Winn’s Brook, the Island End River, and Mill Creek, even in dry weather. Investigations to date indicate the main causes of high bacteria counts in these water bodies to be illicit sewer discharges to storm drain systems and uncontrolled urban stormwater runoff that contains pet and animal waste.

EPA calculates the grades using a three-year rolling average, which allows for a more complete and accurate assessment of recent water quality and is designed to better address weather variability from year to year, while allowing for real data trends to be more easily discerned. Because the grades reflect a three year rolling average, the improvements across the watershed in 2016 indicate that efforts to improve bacterial contamination have been successful. However, regional drought conditions over the past several summers may impact the data, since water quality is impaired more frequently during wet weather conditions than dry conditions. For this reason, EPA and its partners working in the watershed are confident there is still more work to be done.

Throughout the past year there were continued efforts to improve water quality conditions in the Mystic River watershed. Both EPA and the Mass. Dept. of Environmental Protection (MassDEP) continue to pursue a number of active enforcement actions targeted at improving water quality throughout the watershed. These enforcement efforts have resulted in the removal of over 37,000 gallons per day of sewage from storm drains in the Mystic River watershed. Numerous additional illicit connections have been identified and are scheduled to be removed this year. A number of additional repairs have been made that have prevented tens of thousands of gallons of sewage from discharging to the river during rain events.

This spring, EPA signed an agreement with the Town of Belmont, Massachusetts to address stormwater discharges of pollutants to the Mystic River watershed. The agreement, in the form of an Administrative Order on Consent, requires the Town to submit an Illicit Discharge Detection and Elimination Plan, assess its sanitary sewer system, and remove all illicit discharges to the system within five years or according to a schedule approved by EPA. This agreement will have a positive impact on water quality in Mystic tributaries like Winn’s Brook, Wellington Brook, and the Little River.

In a separate effort from our report card for bacteria, during summer months since 2015 EPA has launched a Mystic River water quality monitoring buoy in front of the Blessing of the Bay Boathouse in the City of Somerville. This buoy measures a number of water quality parameters such as temperature, dissolved oxygen, pH, turbidity, specific conductance, and chlorophyll that can be viewed by the public in near real time. The 2015 and 2016 data is available on EPA’s Mystic River Website. In addition to providing real-time water quality data to the public, the buoy is used to monitor for and track cyanobacteria (blue-green algae) blooms. The buoy was launched for the 2017 season on May 31st.

EPA continues to foster a long-term effort to improve this watershed, including continued support of the Mystic River Watershed Initiative Steering Committee. The Steering Committee includes EPA and MyRWA representatives, as well as representatives from other federal and state agencies, and numerous public advocacy groups and municipalities from throughout the Mystic River watershed. The mission of the Steering Committee is to serve as a coordinating and information-sharing body to help establish strategic direction and priorities, as well as to recommend and promote key projects and actions needed to improve environmental conditions in the Mystic River watershed.

More information on EPA’s Mystic River Watershed Initiative (

Contact Information:
Emily Bender ()

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