On Friday, June 26, a sewer main break occurred in Haverhill, and was temporarily repaired Wednesday, July 1st, stopping the ongoing sewage discharge into the river.

MRWC tested the area downstream of the break every day beginning on 6/29/2026. As of 7/10/2026, MRWC concluded that all test sites (with the exception of West Newbury) had returned to normal/expected bacteria levels. We continued to test at West Newbury’s Ferry Park for a longer period as it was the slowest site in returning to normal levels.

In 2025, Ferry Park tested safe 100% of the time during baseline testing. MRWC selected a threshold of 2 consecutive days of safe testing as an indicator that this site had returned to normal/ expected levels. From 7/10-7/20, MRWC tested Ferry Park daily with only intermittent safe results and yet no two consecutive days. During this time, the bacteria levels were also impacted by rain events, to such an extent that MRWC can no longer identify the impact of the Haverhill break during wet weather.

As of 7/21, MRWC will test the Ferry Park site during dry weather (after 3 days of no rain) until the site returns to normal/ expected dry weather levels (2 consecutive days). Additionally, as we wait for the 3-day dry weather period, MRWC will continue to test once a week to monitor Ferry Park.

The public should be aware that even in the absence of an emergency, sites on the Merrimack, especially the mouth of the river, frequently exceed acceptable concentrations of fecal indicator bacteria, which are associated with gastrointestinal illness.

Putting This Event Into Context:

Our Test Sites

Our Test Results

Results in the table below are for bacteria only. A reading of ‘safe’ indicates a fecal coliform level below the recreational limit of either 235 colony-forming units per 100 milliliters for E. coli or 104 colony-forming units per 100 milliliters for Enterococcus.

Test results take 24 hours to incubate so the results in the table below should not be interperted as current information. Defer to public health officials when making the decision to recreate in the river.

Our test results for each site are available in the table below. As of 7/11  we are only testing at Ferry Park in West Newbury. Please note that there is a 24-hour waiting period for each test to allow the bacteria to incubate to a measurable level. The most recent result in the table below will always be from at least 24 hours ago.

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