First tests of summer show good results

A drizzly, light rain greeted monitors on the Souhegan and Merrimack Rivers for the first day of the summer water quality monitoring program.

Tuesday, June 9, began the 13th consecutive year that the Souhegan Watershed Association and the Merrimack River Local Advisory Committee have been monitoring both rivers. All of the monitors are volunteers that spend about a half hour every second Tuesday morning collecting samples.

Although the weather may not have been perfect for the monitors, it is better for the sampling data. Rain washes pollution off the river banks and down storm drains and gives a better indication of possible problems with the water quality.

The data over the past 12 years indicates a cleaning up of both rivers.

Generally the water quality on both rivers is good – at least for the bacteria testing. There are other pollutants in both rivers that the program does not test for however. The Souhegan has shown fairly high counts of lead and phosphorus when tested in the past. The Merrimack is still recovering from decades of dumping by factories along the shore. Creosote is still leaking into the river upstream of Greeley Park.

E. coli bacteria counts showed a fairly clean Souhegan. Counts were slightly elevated as the river passed through the downtowns of Wilton and Milford, but they were still relatively low and generally acceptable. Counts higher than 88 are considered unsafe for public swimming spots and these areas were slightly higher than that, but they met the water quality standards for these rivers.

The Merrimack River between Manchester and Tyngsborough came in with very low E. coli bacteria counts. The highest number here was lower than the best site tested on the Souhegan. This has been true for several years now. As far as bacteria go, the Merrimack is almost always clean except after heavy rainstorms. There were reports of a soapy discharge near the confluence with Salmon Brook, but this did not show up in the tests performed by this program.

Testing for E. coli and dissolved oxygen are performed in the labs at the Milford, Nashua, and Merrimack wastewater treatment plants. Temperatures and observations are done by the monitors in the field.

The next test will be done June 23.

The Nashua River Watershed Association monitors the entire length of that rover once a month during the summer.

Past test results are also shown on the SWA website (

A number of the sites were not tested due to lack of volunteers to monitor the sites.