also points to needs for improvement
The latest 2020 Water Quality Report Card for the Mystic River watershed shows that water quality remains an “A” for the Mystic Lakes, and a “B+” for the main stem of the river.
“This is great news, as it means our urban river continues to be a valuable asset for all our community members to use and enjoy,” said Patrick Herron, Executive Director. “The reason we are seeing this grade is thanks to decades of serious investments to clean up Boston Harbor and its rivers, as well as the growing commitment by our municipalities to make local infrastructure improvements.”
But some streams that flow to the Mystic remain seriously impaired. The water bodies marked yellow and the red on the map are seeing bacteria counts that violate water quality standards much of the time. On average, fewer than 20% of samples from Alewife Brook, for instance, met state standards for swimming, contributing to the stream receiving a grade of F. The cause of this lower grade is bacteria introduced into the watershed by raw sewage, which reaches waterways via leaking pipes, illicit connections, and combined sewer overflows (CSOs).
To address these issues requires infrastructure improvements targeted at these water bodies. One such tributary, Island End River, did get that investment and it paid off. In just three years has gone from earning a “D” for water quality to this year's grade of an “A+.” After extensive testing and detective work, the City of Chelsea discovered a sewage pipe from a large building that had been installed incorrectly--dumping sewage directly into the creek. This pipe was corrected, and the grade for the tributary has steadily improved.
“The two big takeaways from the report card are 1) go out and enjoy your healthy urban river, and 2) we need to make continued infrastructure improvements to those tributaries that are not meeting the grade,” said Andy Hrycyna, Watershed Scientist. “We don’t have to have failing grades--if we invest in policies and infrastructure. The success at Island End shows this.”
Since 2014, the EPA has assigned grades to 14 separate water bodies in the Mystic Watershed based on levels of bacteria contamination. Much of the field sampling work is done by a cohort of volunteers from the Mystic River Watershed Association, who sample at 15 locations every month no matter the weather, as well as data provided by MWRA. The report card is then published in the summer of every year.
Snapshot of the Grade:
Mystic Lakes & River: The green means that the water is healthy to boat and swim in on most days. In dry weather, they are safe for canoeing and kayaking almost all the time. This is the seventh year in a row that we have seen such high grades on these bodies of water. Remember if you want to see if there is high bacteria on the day you want to paddle--use MyRWA’s predictive boating advisory here.
Alewife Brook: There are multiple active Combined Sewer Overflows on Alewife being managed by the City of Cambridge and the City of Somerville. With heavy rains -- like the precipitation we have seen in July 2021 -- the systems get overwhelmed, and dump raw sewage into the stream itself (instead of backing up into our streets and homes). The Massachusetts Water Resource Authority (MWRA) is undertaking a period of measurement to determine whether more investments are required to meet the standards agreed to in the Long Term Control Plan (LTCP) of the Boston Harbor Cleanup Plan.
Winn Brook: The Town of Belmont is actively investing in finding sources of contamination to Winn Brook as part of a court-ordered improvement plan. Additionally, though not shown the map, Belmont is also investigating issues with Wellington Brook, which as well has poor water quality. The most likely reason is old infrastructure, many decades-old pipes that need repair.
Aberjona & Malden River: The Aberjona and the Malden River do not have CSOs, instead the bacteria is more diffuse--coming from leaky and old infrastructure, as well as stormwater pollution. To address stormwater pollution, green infrastructure is a cost-effective nature based solution that MyRWA is piloting around the watershed including infiltration trenches and constructed wetlands.
Further Resources:
WBUR: Boston Rivers Were Pretty Clean In 2020, But Sewage Is Still A Problem Says EPA
Boston Globe: Boston-area water quality report cards show widespread improvement, but still range from A to F
REport card Q & A:
How do the C rated rivers flowing into the Upper Mystic Lake lead to an A rating for the lake?
Mystic Lakes are essentially a large holding reservoir. During the time that the water from the Aberjona River sits in this lake, sunlight and settling does much to reduce the bacteria levels. They are also large, deep lakes relative to the volume of water entering, and so dilution almost certainly plays a role. The outcome is that by the time we measure the levels of bacteria at the other end of the lake, bacteria levels are near the bottom of detection limits.
Recognizing the grades are an average for the whole year, how would one know whether it's safe to swim or boat on any given day?
Whether you’re rowing, kayaking or swimming, we want users of the Mystic to be able to make informed decisions about their activity. Use MyRWA’s Daily Boating Advisory--which shows estimates of water quality conditions generated by an automated bacteria prediction model--to find out if it’s safe for recreation. This model is based on a data-intensive study that looked for correlations between bacteria levels and a variety of environmental variables, especially recent rain. The predictions are made each day at 5 AM and are valid for the remainder of the day.
Do the letter grades have practical meaning? For example, is an A drinkable water and B would be swimmable?
The letter grades themselves are suggestive rather than tied to specific activities. And we would never recommend drinking untreated water from any urban water body. But many of the water bodies in the Mystic watershed are swimmable and boatable on a regular basis. For the percentages of our water quality samples that met boating and swimming public health standards, under different environmental conditions, look at the graph and table at the bottom of this page. You will see, for instance that in dry weather conditions (less than .25 in of rain in the last 48 hours, “boat/dry” on the table) the Mystic River meets the safe boating standard and Upper Mystic Lake meets the swimming standard more than 95% of the time.
Do the different readings generally agree? For example, are waterways with high bacterial counts also have high phosphate levels?
There is some correlation with bacteria and phosphate levels, but we have not performed a detailed analysis. A good example is that big precipitation events yield both high bacteria and high nutrients in the river. That said, the nutrients are mostly from the street surfaces and the bacteria is mostly from sanitary systems leaking into the stormwater system. Learn more about the different types of pollution entering our waterways (stormwater pollution vs. CSOs) here.
How do you get on the list for the MWRA instant CSO notification list?
You can sign up for MWRA notifications at: http://www.mwra.com/updates/everbridge/join.html
How does shoreline restoration figure into improving water quality?
Shoreline plantings -- and riverine vegetated buffers in general -- are valuable as a kind of natural “green infrastructure.” Plants prevent soil and bank erosion, keeping sediments and excess nutrients--especially phosphorus--from reaching the stream, and the plants themselves take up phosphorus, acting as a kind of filter. Somewhat counterintuitively, urban landscapes are disproportionately high contributors of excess phosphorus to water, and this can lead to cyanobacteria and algae blooms and invasive plant overgrowth and degradation of aquatic habitat. That is why, after bacteria, a major focus of our water quality work and advocacy has been around phosphorus. For more on that long-term effort, see our webpage on nutrient pollution and the recently published Alternative TMDL Report on phosphorus in the Mystic published by EPA in collaboration with DEP, MyRWA and many other partners.
