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water pollution garbage

While there are many different sources that contribute to river pollution, the most frequent causes in Massachusetts are:

Stormwater Runoff

Stomwate Runoff

When rainwater hits paved surfaces, it can't soak into the ground, and instead runs along streets and parking lots picking up pollutants as it moves. This polluted runoff flows into our rivers and streams, degrading water quality, and can overwhelm local infrastructure to cause sewage overflows. 


Stormwater runoff is recognized by the EPA as the #1 source of water pollution in Massachusetts and the primary reason why more than half of our waterbodies are considered “impaired.” 


Grey infrastructure channels rainfall and snowmelt into storm drains and pipes, and dumps it into waterways. The consequences are the loss of groundwater recharge, reduced base flows in streams, increased flooding, and lower water quality.

Green infrastructure, on the other hand, is a nature-based method of water management that benefits the environment and economy by mimicking the natural system and directing stormwater back into the ground. Green infrastructure reduces flooding by using soil and vegetation to replicate the natural hydrologic cycle. Typical practices include installing permeable pavement in urban areas and developing rain gardens and riparian buffers along streams and rivers to help slow, filter, and store polluted runoff before it reaches our waterways.

The State's stormwater information page, including federal, state, and local permitting >>

The Massachusetts Stormwater Handbook >>

Think Blue Massachusetts explaining stormwater >>


How are we working on this issue at Mass Rivers?


We are working with the state, federal government, and many partners to improve regulations that minimize stormwater runoff, incentivize green infrastructure and nature-based solutions, and secure funding for communities to implement environmentally-friendly means for reducing stormwater runoff. Past projects have included litigation to require the EPA to implement a long-delayed stormwater permit, and a series of workshops to help municipal staff and consultants implement stormwater utilities as a mechanism to pay for stormwater management costs.

Check out our Stormwater Spotlight: Greater Boston, featuring three local stormwater experts!

water puddle on street
water pollution flows out to the ocean from the Merrimack River at Salisbury Beach after Tropical Storm Irene in 2011

After a storm, stormwater and sewage enter our rivers in high volumes. Climate change will bring more storms to our region, making events like this more frequent with our current infrastructure.


Here, pollution flows out to the ocean from the Merrimack River at Salisbury Beach after Tropical Storm Irene in 2011. The brown color you see is primarily erosion and storm runoff as well as sewage. Bacteria levels soared in Newburyport, forcing the city to close the beaches on a very sunny and warm Labor Day weekend.

Photo Credit: Ron Barrett

Learn more about stormwater:

Video made by Jiawen Xu and Xinyu Lu for Boston Scope. Read the article >>

Sewage Pollution

Sewage Pollution

In some parts of our state, communities still have combined sewer overflow (CSO) infrastructure. These combined systems collect both sewage and rainwater into one pipe. Under normal conditions, these pipes transport all of the collected wastewater to a sewage treatment plant, then discharge the treated water to a waterbody. During heavy rain, the amount of water entering the pipes exceeds their capacity, so, by design, the pipes discharge some of the untreated mixture into a waterbody.


CSO discharges are a priority water pollution concern for the EPA, since they contain untreated or partially treated human waste, industrial waste, toxic materials, debris, and stormwater. As of 2018, nearly 860 municipalities across the U.S. still have CSOs. In Massachusetts, as of 2019, 19 communities currently have CSO infrastructure. 

overflowing storm drain

These sewage overflows are disastrous for public health and our rivers. Untreated human sewage teems with salmonella, hepatitis, dysentery, cryptosporidium, and many other infectious diseases. Sewage releases can warm waterways, impacting both water temperature and water quality while disrupting aquatic ecosystems. 


Over the last decade, Massachusetts communities have invested roughly $1 billion to address CSO pollution issues. Unfortunately even with those investments, Massachusetts is still discharging approximately three billion gallons of sewage into the water every year.

How are we working on this issue at Mass Rivers?


In 2021, Governor Baker signed a law requiring sewer operators to notify the public when and where raw or partially treated sewage has entered waterways. Working with many partners, Mass Rivers led advocacy efforts for this bill so that residents would no longer unknowingly come into contact with harmful bacteria from raw sewage.

Learn more about the bill's journey >>

See the 2022 Sewage Notification Annual Report >>

Notification, however, is only the first step. Public awareness of how our sewer system works, and the challenges it poses, will increase support for upgrades to modern infrastructure. Replacing a combined sewer system is an expensive investment, but a critical and necessary one for water quality and public health. 

PFAS and Pesticides

PFAs and Pesticides

Contaminants of emerging concern enter the environment every day. Emerging contaminants refers to many different kinds of chemicals, including medicines, personal care or household cleaning products, lawn care and agricultural products, among others. These chemicals eventually travel to our rivers and streams (via stormwater runoff, groundwater leaching, untreated discharges etc.) and have a detrimental effect on fish and other aquatic species. These contaminants have also been shown to bioaccumulate up the food web - putting even non-aquatic species at risk when they eat contaminated fish.

PFAS is a class of chemicals that are especially harmful and do not breakdown in nature. Recently, the pesticide used by the State for mosquito control was found to contain PFAS (Read the Boston Globe article detailing the findings). 

Department of Environmental Protection's PFAS testing program for public water suppliers (see if your town has been tested) >>

EPA information on PFAS >>

Mosquito info (including how to opt-out of spraying) >>

These chemicals come from products we use everyday in our homes, like cleaning agents and non-stick cookware. Wastewater treatment plants weren't designed to remove these chemicals, so treated wastewater can carry toxins back into waterways. Similarly, industrial processes that have their own treatment processes don’t remove all these chemicals, either. Eventually, they end up in our waterways, impacting wildlife and water quality.

How are we working on this issue at Mass Rivers?

As part of the Mosquito Control for the Twenty-First Century Task Force, we are involved with reforming the current pesticide regulations  in favor of safer, nature-based solutions. Learn more about how to make your voice heard on the task force >>


As new information emerges about new or existing contaminants and potential impacts to both public health and the environment, we work closely with state and federal regulators and other partner organizations to make sure that the strongest possible protections are put into place, based on current science.

The Boston Globe, May 31, 2021: "As contaminated water concerns grow, Massachusetts towns urge the state to stop spraying pesticides in their communities."

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