PRESS RELEASE
Haverhill Sewer Main Break
More River Sites Show Unsafe Bacteria Levels
* New information different from yesterday’s press release is highlighted in yellow *
July 1, 2026. Haverhill, Massachusetts – The second day of sampling the Merrimack River at sites downstream of the Haverhill sewer main break indicate that more areas of the river have dangerous fecal bacteria levels.
The Merrimack River Watershed Council (MRWC) began testing on Monday, June 29th, and posts the results online 24 hours later (due to incubation and lab processing time). Seven sites are tested, from Haverhill to the mouth of the river. Monday’s samples indicated three of the seven sites had unsafe bacteria levels. Tuesday’s samples (newest data) indicated that five sites had unsafe bacteria levels, with one site (Ferry Park in West Newbury) above 25x the safety limit for E. Coli.
MRWC recommends that people do not engage with the Merrimack River downstream of Haverhill, including Newburyport Harbor, until further testing can validate that it is safe to do so. Unsafe conditions will likely extend through the July 4th Weekend.
Unsafe levels of fecal bacteria can cause gastrointestinal diseases, infections and even death. The levels detected are unsafe for humans and pets. Young people, the elderly and those with compromised immune systems are at greatest risk.
MRWC will continue to post daily test results on its website (www.merrimack.org) until the bacteria levels return to normal. Test results are compared to EPA safety limit and are conducted at MRWC water quality testing sites with several years of historical data.
On Friday, June 26, a sewer main break occurred in Haverhill. As of today, the City of Haverhill reports that the first of two diversion pipes have been installed that should be able to keep discharge from going into the river as long as the volume remains under Haverhill’s regular sewer flow. A second diversion pipe should be in place within a few days to keep sewage and storm water from discharging into the river during rain events. Prior to the repair, the overwhelming majority of Haverhill’s sewage was being discharged directly into the Merrimack River at an estimated rate of 7-10 million gallons a day. The pipe involved was a 50-year old 42” concrete main. As initial evaluation work was done on the site, a second break in the line was also discovered several hundred feet up from the first break.
To understand the impact of the break and the resulting release of raw sewage, it is important to put the discharge into perspective. Haverhill has an average of 35 combined sewer overflow (CSO) events in a year. A median Haverhill CSO discharges roughly 60,000 gallons. However, a large Haverhill CSO (top 2%, or roughly once every 2 years) can discharge approximately 10 million gallons. Typical Haverhill CSOs impact an area immediately downstream for roughly 3 days and do not significantly impact the bacteria levels beyond the Artichoke River in West Newbury. In this context, the sewer main break is a major disruption above and beyond what is typically discharged into the Merrimack River.
There are at least two additional factors to keep in mind when putting this unprecedented event into context. First, the discharge from the sewer main break is 100% sewage, not diluted with storm water run-off, as is the case during a CSO. Second, this was an ongoing and compounding discharge. Both factors are likely to make the bacteria levels higher and the area of impact larger than a CSO of this magnitude.
While this event is a concern for people and wildlife during the time bacteria levels are elevated, it is not necessarily a long-term catastrophe for the river. This in no way diminishes the current safety and health concerns. It does, however, give hope for the river’s capacity for recovery.
