BOSTON — More than 800 million gallons of raw or partially treated sewage spewed into the Merrimack River last year from aging pipes that were supposed to be sealed up years ago.
The sewage came from about 50 overflow pipes that are part of decades-old sewer and stormwater systems designed to overflow when they are inundated, usually because of heavy rain.
Last year, five sewage systems along the 117-mile Merrimack River reported hundreds of discharges amounting to more than double the 400 million gallons of sewage dumped into the river in 2017, according to data compiled by environmental activists and regulators.
Statewide, outfalls along other major rivers discharged more than 3.4 billion gallons of sewage.
While a permanent fix is years away, lawmakers and environmental groups are pushing for quicker, more widespread notification of overflows to keep the public informed.
Legislation co-sponsored by Rep. Linda Campbell, D-Methuen, would require sewage system operators to notify the public and local boards of health in affected communities within two hours of an overflow. State environmental regulators also would be required to post details of the overflows and provide regular public updates on their website.
Gabby Queenan, policy director at the Massachusetts Rivers Alliance, said the state's current notification rules are inadequate.
"We fall short of that basic, essential right of letting Massachusetts residents know what precautions they need to take when it comes to protecting public health," she said at a briefing on the proposal Thursday. "This bill is simple: Let the public know when there is sewage in local waterbodies so they can take the necessary precautions."
Similar proposals have been filed in the past. Supporters say they believe awareness of the issue on Beacon Hill has increased in recent years amid more frequent and large discharges into the state's rivers.
House and Senate versions of the bill are backed by more than 80 lawmakers, both Democrats and Republicans.
The overflows violate the federal Clean Water Act but the sewage treatment districts, which predate the law, operate under consent agreements with the U.S. Environmental Protection Agency that allow discharges during heavy rains and other events.
Under state law, publicly regulated sewage treatment systems are required to notify the Department of Environmental Protection immediately after a discharge and no later than 24 hours.
Exactly who is notified varies depending on state and federal permits, the size of the treatment system, where the overflow pipe is located, and if water is drawn downstream for drinking.
Environmentalists say large and frequent overflows — and the lack of notification — pose health risks to those who use the river for boating and swimming, as well as communities that draw drinking water from it.
"There's a huge amount of raw sewage that goes into our rivers, and the reality is most people don't even know about it," said Rusty Russell, executive director of the Merrimack River Watershed Council, which monitors discharges into the river. "And the problem doesn't go away when the rain stops."
Untreated sewage carries pathogens such as fecal coliform and bacteria that can cause dysentery, hepatitis and other gastrointestinal diseases.
Sewage treatment system operators say discharges account for only a small portion of tens of billions of gallons of sewage treated every year.
They also note that discharges are diluted by river water — a 2004 government study noted the flow of the Merrimack in Lowell is about 57,000 gallons per second — decreasing potential health risks within a few hours.
An estimated 600,000 people get their drinking water from the Merrimack, including 80,000 in Lawrence.
A 2015 study published in the journal Environmental Health Perspective found a significant increase in people visiting hospital emergency rooms with gastrointestinal illnesses following raw sewage discharges into the river in the Lowell, Andover and Lawrence area.
Raw sewage also causes algae blooms, which can be toxic to people and deprive water bodies of oxygen, killing fish and other marine life.
The Greater Lawrence Sanitary District in North Andover — which processes waste from Lawrence, Methuen, Andover, North Andover, Dracut and Salem, New Hampshire — released at least 93 million gallons of sewage into the river last year, according to state data complied by the Watershed Council.
In Haverhill, the sewage treatment system dumped 49.5 million gallons into the river last year through 15 outfalls.
Lowell's sewage treatment system reported the most overflows on the river last year, or about 245 million gallons worth through eight outfalls on the river.
In New Hampshire, the Manchester sewage district was one of the worst polluters in terms of quantity among five facilities along the Merrimack, releasing an estimated 364 million gallons of sewage through 15 outfalls, according to the state Department of Environmental Services.
Newburyport Mayor Donna Holaday said she has witnessed the serious environmental, health and economic impacts of sewage discharges into the river.
"I have seen pictures of dogs with sores all over their bodies from swimming in the river after CSO discharges," she said. "It would make you sick."
Holaday said while a long-term solution could "cost millions and millions of dollars" and take years, the public needs to know in the interim when sewage discharges have occurred.
"The very first thing we need to do is to be able to notify the public," she said. "We have to notify families, children, boaters and fisherman that the river is loaded with bacteria."
Christian M. Wade covers the Massachusetts Statehouse for North of Boston Media Group’s newspapers and websites.