Walking along Boston Harbor today, it’s hard to believe that this bustling waterfront was ever anything but beautiful and vibrant. Yet 30 years ago, Boston Harbor was filled with so much sewage and toxic pollution that its dirty water became notorious. And it was deemed a problem too big, too dirty, too political and too expensive to solve.

Turns out, it was a problem that could be solved. It took many people working together toward the common dream of a clean harbor. Residents, legislators, lawyers and others spent years on this effort.

The city of Quincy and Conservation Law Foundation took the state (and, for a time, the United States Environmental Protection Agency) to federal and state court.

The Legislature created and funded the Massachusetts Water Resources Authority to oversee the proper treatment of all Greater Boston’s wastewater before it enters the ocean. Some of the best engineers and construction teams around developed the current wastewater treatment facilities, both on time and under budget.

Finally, residents did their part by agreeing to the higher sewer charges necessary to build and operate a sewer plant that actually worked.

Fast forward to 2022: People can swim and fish in Boston Harbor; the Harbor Islands are a national recreation area; and billions of dollars have been invested in real estate surrounding the water.

It’s been a long road to get here, but those successes are only tenable as long as there are people committed to maintaining them. Which is why Conservation Law Foundation continues our dogged effort to ensure our coastal waters remain clean and habitable. Unfortunately, the wastewater from our homes and the area’s hospitals and manufacturing facilities can now threaten decades of progress.

The MWRA’s job is to ensure cities, towns, hospitals and other industrial facilities pretreat their wastewater before it is pumped to the Deer Island treatment plant and then discharged into Massachusetts Bay.

The problem is that MWRA recently has not been effectively setting and enforcing pollutant limits and other treatment requirements, which could put our coastal waters in danger.

Even the smallest amounts of excess pollution add up in a region as large as Greater Boston, with homes, industrial and commercial facilities all sending wastewater to the Deer Island facility every day. Especially if the excess pollution is happening repeatedly.

Improperly treated wastewater impairs water quality and can harm local ecosystems and aquatic life. Harmful pollutants like mercury and zinc are found in wastewater and can be disastrous for the plants and animals that live in the harbor and surrounding waters. These substances also build up in the bodies of fish and can make humans sick.

During the warmer months, locals and tourists flock to Boston Harbor to boat, sail and swim. No one should have to wonder if there’s improperly treated industrial waste washing ashore, lapping at the sides of their boat or surrounding their children while they play in the waves.

The effort to clean up Boston Harbor began in the 1970s. It took decades and more than $4 billion to get to where we are today: a safe, clean harbor that is the envy of many cities. Now is not the time to let down our guard.

The community joined together then and vowed to never allow the harbor to become a toxic mess again. MWRA must be held accountable and do its job today to keep pollution at safe levels and protect the waters that belong to all of us.

Peter Shelley is Senior Counsel at Conservation Law Foundation. Heather Govern is the organization’s Vice President of Clean Air and Water.