BOSTON — Regulators are pressing the operators of three sewage treatment systems along the Merrimack River to reduce the bacteria flowing into the river and to issue more timely alerts when raw sewage discharges through aging outfall pipes.

The three systems — tied to the Greater Lawrence Sanitary District in North Andover, Haverhill’s treatment plant and another plant in Lowell — operate under consent orders with the U.S. Environmental Protection Agency. Permits for all three expired several years ago. The EPA posted draft copies of renewed agreements late Friday afternoon.

The EPA said in an advisory the new permits will include heightened monitoring and reporting requirements, while calling for additional treatment of sewage to reduce bacteria and other pollutants “to address potential adverse impacts to aquatic life, recreation and drinking water uses due to the discharges of treated wastewater and combined sewer overflow.”

The feds also want to require sewage system operators to notify the public and local boards of health in affected downriver communities within four hours of a raw sewage discharge from any of 27 combined sewer overflow pipes.

Plant operators also would be required to compile data on spills and provide it to the feds, state and local governments.

Designed long before the Clean Water Act was written into law in the early 1970s, the treatment 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 of untreated sewage spewed into the river from about 50 overflow pipes.

“The segments of the Merrimack River that receive discharges from these three wastewater treatment plants and associated CSOs have been identified by MassDEP as impaired for bacteria, PCBs and total phosphorus,” the EPA advisory stated.

Environmentalists who monitor the river welcomed the tougher requirements, saying they will improve water quality and public awareness. The EPA will collect public comment on the draft agreements over the next 30 days.

“We believe this is a step in the right direction,” said John Macone, interim executive director of the Merrimack River Watershed Council. “We’re absolutely in support of what the EPA is trying to do.”

Macone said the long term goal of closing up the outfalls will likely require hundreds of millions of dollars in federal funding, which isn’t forthcoming.

“It’s a big bill and obviously cities and towns along the river can’t come up with the money,” he said. “They need federal help.”

The increased scrutiny of the plant operators comes amid heightened health and safety concerns about sewage discharges into the Merrimack and other protected rivers.

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

140 million gallons

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.

On Beacon Hill, lawmakers have filed dozens of bills aimed at more widespread notification of overflows to keep the public informed.

Statewide outfalls along other major rivers discharged an estimated 3.4 billion gallons of sewage last year.

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.

Raw sewage also causes algae blooms, which can be toxic to people and deprive water bodies of oxygen, killing fish and other marine life.

For additional details about the proposed EPA permits and to comment on them: https://www.epa.gov/npdes-permits/massachusetts-draft-individual-npdes-permits

Christian M. Wade covers the Massachusetts Statehouse for The Salem News and its sister newspapers and websites. Email him at cwade@cnhi.com.