BOSTON – Lawmakers are pressing for new rules to keep the public informed about sewage discharges into the Merrimack River from aging sewer systems.

On Tuesday, the Legislature's Joint Committee on Environment, Natural Resources and Agriculture heard testimony on several bills that seek to improve notification about the discharges.

Designed long before the Clean Water Act was written into law in the early ‘70s, the systems along the river collect stormwater in the same pipes as sewage, and are designed to overflow when they become inundated, usually because of heavy rain. Last year, more than 800 million gallons spewed into the river from about 50 overflow pipes.

Environmentalists say large and frequent overflows pose health risks to boaters and swimmers, as well as communities that draw drinking water from the river.

A proposal by Rep. Linda Campbell, D-Methuen, would require sewage system operators to post signs near outfalls and notify the public and 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 online updates.

"This is a public health and safety issue," Campbell told the panel. "We anticipate that these spillages are going increase in both volume and intensity. And we also know that the demand for drinking water up and down the Merrimack River is going to increase exponentially."

Another proposal, filed by Sen. Diana DiZoglio, D-Methuen, would require the state Department of Environmental Protection to develop a color-coded warning system to be displayed with safety flags at beaches, boat launches and areas along the Merrimack River, to notify the public when discharges have occurred.

Under state law, publicly regulated sewage treatment systems are required to notify the DEP immediately after a discharge and no later than 24 hours.

But who gets notified varies widely depending on the size of the facility, where it is located, and if water is drawn downstream for drinking.

Another proposal, filed by Reps. Lenny Mirra, R-West Newbury, and Jim Kelcourse, R-Amesbury, also would require state regulators to come up with a discharge notification system.

"We need to make this a priority," Mirra told the panel. "We're seeing a spike in gastrointestinal illnesses in our emergency rooms when these sewage outflows occur."

Campbell has also filed legislation that would require sewage treatment facilities to have back-up power systems not connected to the regional electrical grid and to submit to frequent inspection by environmental regulators to ensure those systems will function if needed.

A power outage at the Greater Lawrence Sanitary District's treatment plant in North Andover in 2017 resulted in a spill that discharged an 8 million gallons of untreated sewage into the river. Federal and state regulations require treatment plants to have back-up power, but the reliability of the systems varies.

Consideration of the bills comes amid heightened health and safety concerns about sewage discharges into Merrimack and other protected state rivers.

Last year, five sewage treatment systems along the 117-mile Merrimack River reported hundreds of discharges of more than 800 million gallons of sewage into the river, according to the state Department of Environmental Protection.

The Greater Lawrence Sanitary District – 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 the department.

Haverhill's treatment system dumped 49.5 million gallons into the river last year.

Statewide outfalls along other major rivers discharged an estimated 3.4 billion gallons of 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 fast-moving river water, decreasing potential health risks within a few hours.

But untreated sewage carries pathogens such as fecal coliform and bacteria that can cause dysentery, hepatitis and other gastrointestinal diseases.

And an estimated 600,000 people get their drinking water from the Merrimack, including 80,000 in Lawrence.

Municipal leaders downriver say they want the state and federal governments to step up with funding to close down the outfalls. In the interim, they want the state to set up a better system of notifying the public about the discharges.

"Every time it rains we have a potential public health issue," Amesbury Mayor Ken Gray told the panel. "We need to let people know in a timely fashion when its dangerous to be in or on the waterways."

Christian M. Wade covers the Massachusetts Statehouse for The Eagle-Tribune. Email him at cwade@cnhi.com