Andover residents should avoid all contact with the Merrimack River until at least Thursday evening, July 23, after the Lowell Wastewater Treatment Facility discharged untreated or partially treated sewage into the waterway Tuesday night.

The Town of Andover posted a public health advisory on Tuesday, July 21, stating that a combined sewer overflow at the Lowell facility released wastewater into the Merrimack River between 6:30 p.m. and 12:05 a.m. The state recommends people stay out of the river for at least 48 hours after the start of a discharge event because of elevated bacteria and pollutants.

What residents should do

The town's advisory does not specify a formal all-clear process or water-quality testing schedule. Residents who kayak, fish, or swim in the Merrimack should monitor andoverma.gov for updates. Based on the 48-hour avoidance window measured from the start of the discharge, the advisory period expires no earlier than approximately 6:30 p.m. on Thursday, July 23.

Andover has more than 5 miles of Merrimack River shoreline, including the Deer Jump Reservation kayak launch at Brundrett Avenue.

Second overflow this month

This is the second time in July that the Lowell plant has triggered an Andover advisory. A prior overflow on Monday, July 7, lasted from 2:15 p.m. to 11:28 p.m. and carried the same 48-hour warning.

The advisory was issued under state regulation 314 CMR 16.09, which requires municipalities downstream of a discharge to notify the public.

Health risks

Combined sewer overflows carry bacteria that can cause rashes, infections, and gastrointestinal illness in people and animals, according to the Massachusetts Department of Public Health.

The July 21 overflow adds to a difficult stretch for the river. Earlier in July, a separate emergency in Haverhill dumped 8 million gallons of raw sewage per day into the Merrimack after a 42-inch force main broke in two places at the Haverhill wastewater treatment center. Swimming at Plum Island and Salisbury Beach State Reservation was prohibited until water quality testing cleared those beaches on Thursday, July 3.

Gov. Maura Healey said on July 3, when announcing the beaches had reopened, that she was "glad that people can once again enjoy swimming at our beaches just in time for the Fourth of July weekend."

As of 2024 reporting by the Merrimack River Watershed Council, the Lowell facility accounted for roughly 41 percent of total annual CSO volume discharged into the river. Lowell is under an EPA order to spend more than $300 million on a pipe-separation project expected to take at least a decade, according to the same 2024 MRWC report.

No named Andover official was available for comment on the July 21 advisory. The next update, if any, will be posted at andoverma.gov.