Don’t love that dirty Souhegan River water
>High bacteria counts found in Wilton
WILTON – The Souhegan River flowing through downtown Wilton earlier this month was teaming with E. coli bacteria – more than six times the amount considered unsafe for swimming.
Volunteers from the Souhegan Watershed Association took samples of river water between Ashburnham, Mass., and Watson Park in Merrimack on Tuesday, Aug. 9, and in downtown Wilton, bacteria levels read at 770.1 cfu/mL, the highest for the entire length of the river. Numbers above 126 mean swimmers have a good chance of getting sick with an ear or eye infection or a gastrointestinal illness.
E. coli is the bacteria found in animal and human intestines and considered a good indicator of water cleanliness. Cfu (colony-forming unit) is a measure of viable bacteria cells per milliliter. The safe range for cfu’s is 88 and below.
"At 406, it’s dangerous," SWA President George May told the Milford Conservation Commission last week.
The good news is that upstream, at the popular Wilton swimming area called the Horseshoe, the E. coli reading was very low – 42.8 cfu/mL.
But at the Boston Post Road canoeport in Amherst, the number was almost double the safe cutoff for swimming – 172.3.
Bacteria levels were high in the river throughout downtown Milford, as well, and didn’t drop below 88 cfu’s until the town of Merrimack, reaching a low of 30.5 at Watson Park.
May said low flows, caused by the lack of rainfall, were partly responsible for the bacteria, because low flow means water and its pollutants, including animal and bird feces, is less diluted.
On the other hand, heavy rain brings bacteria into the river.
The river flows north out of Massachusetts through Greenville, where it is fairly fast-moving, and then slows down in Wilton and Milford, which also accounts for a natural accumulation of bacteria, he said.
The SWA has been monitoring the river for 20 years. May was invited to the commission meeting because the organization had asked for a $100 donation, which the commission voted to approve.
Thirty volunteers monitor 20 river sites, six of them in Wilton. Twelve sites are on the Merrimack River, most of which tested exceptionally clean on Aug. 9, except for the one near Arms Park in Manchester.
Test results can be found on the SWA’s Facebook page each Wednesday. The final test of the season was Tuesday, Aug. 23.
According to SWA’s website, primary threats to the river are "nonpoint" sources of pollution, including fertilizers, pesticides and herbicides, as well as septic systems, storm runoff and soil erosion. May told commission members he is happy to see the newly painted storm drain indicators around town. They remind people not to dump pollutants down the drains, because they wind up in the river.