Latest E. coli test results for Souhegan, Merrimack rivers

The final Souhegan Watershed Association (SWA) water quality monitoring testing for this season took place on a clear, sunny day for a welcome change by the monitors. This summer it seems most of the test dates were on or just after rainstorms. While the rainstorms provide the most beneficial data, the clear weather was appreciated by the volunteers. Several appreciated not having to negotiate slippery rocks and muddy trails.

The Merrimack River returned to excellently low E. coli counts with one exception. A water sample taken near the Taylors Falls Bridge in Nashua had a count of 866.4, almost 10 times greater than what would be allowed for public swimming beaches. The rest of the river between Manchester and Tyngsborough tested well below the 88 threshold for a public beach. The prior two tests taken this summer had unusually high counts – probably attributed to runoff from work being done at the Amoskeag Dam in Manchester. Typically the Merrimack River has low E. coli counts, like what was seen on most of the sites tested this week.

Work on the Pawtuckett Dam in Lowell, which backs up water as far as Merrimack, has been completed and the river level is slowly returning to normal levels. Eventually the planned replacement of the plywood ‘boards’ with a modern inflatable bladder like the one recently built at the Jackson Falls Dam near Margarita’s in Nashua will correct the long overdue problem of raising and lowering the river and messing up summer recreation, the habitat and erosion.

SWA tests the entire length of the Souhegan River from Ashburnham, Mass., to the mouth of the river in Merrimack, N.H. This river flashes up and down like a small river is expected to do. Typically the upstream section from Ashburnham downstream as far as Wilton has very acceptable E. coli counts. And that’s what the tests found this week. The test at Water Loom Pond in New Ipswich was only 5.2, excellent. Further downstream at The Horseshoe in Wilton, a popular swimming hole, the count was 24.6, still excellent.

As the river runs into population centers in Wilton and Milford, counts typically go up, usually to unacceptable levels. The levels were not as high as usual this week, but they were once again unacceptable. The E. coli level at the Swing Bridge in Milford was 290.9, well into the unacceptable range.

Typically the counts remain high as the river slows down and becomes more shallow and sandy through Amherst. Another spot where kids hang out at the Boston Post Road Canoeport near Souhegan High School in Amherst was a bit better than usual, but still a barely acceptable 121.1.

The river cleaned up in the more rural parts of Merrimack, but the count at the popular swimming spot at Watson Park in Merrimack was 129.6, slightly higher than acceptable and is posted with a red flag to indicate that swimmers there are exposing themselves to ear and eye infections and gastrointestinal problems. This site will be tested for the last time this season on Aug. 31.

Besides the usual reports of ducks, herons and animal tracks, monitors reported lots of colorful flowers and especially Cardinal Flowers all along the Souhegan shoreline. An osprey was even spotted flying over the river near downtown Milford.

This summer both rivers returned to a more normal life. Last year at this time we were in a drought condition that severely impacted the Souhegan that required a couple of interventions to prevent loss of habitat. The Souhegan now has requirements to protect the river flow during severe conditions. This year no watering restrictions have been needed.

This is the final test for this season. Thirty volunteers collect samples from their specific site along and transport the samples to one of the wastewater treatment plants in the area where certified technicians prepare and read the results. E. coli samples require an incubation period of 24 hours before the results are available. The labs at the wastewater treatment facilities in Manchester, Nashua, Merrimack, Milford and Greenville all are critical partners in this program.

Volunteers are always welcome to replace retiring volunteers; they can contact George May at for more information. Some of our present volunteers have been with the program since its inception more than 20 years ago. The plan is to continue monitoring beginning again next June.