Merrimack watershed bacteria results: July 23, 2019

Dear River and Watershed Friends,

Upper Merrimack Monitoring Program volunteers continue the bacteria sampling season with 100% sampling at 100% of the eleven sites on the Merrimack River from Franklin to Bow and on the Pemigewasset, Winnipesaukee, and Contoocook Rivers. 

The results shown below are the probable number of E. coli bacteria colonies for every 100 millilitres of water. Warm blooded animals (including humans) all have E. coli in their guts. State designated swim beaches are not allowed to exceed 88 colonies and Class B waters (all of our sites are Class B waters) should be below 406 colonies. Here are the details.

Site number and description
1 Pemigewasset41
2 Winnipesaukee185
3 Merrimack above FWWT Plant63
4 Merrimack below FWWT Plant213
5 Merrimack Jamie Welch Park63
6 Merrimack Route 4 Bypass41
7 Contoocook at Rivco134
8 Merrimack Sewalls Falls31
9 Merrimack Manchester St63
10 Merrimack Blue Seal160
11 Merrimack Garvins Falls146

All sample results are as of Tuesday morning, July 23, 2019. Results may change from day-to-day, depending on upstream conditions and rainstorms.

The story this week is that we are seeing some elevated numbers compared to two weeks ago. You will recall that up until this past Tuesday, it has been very dry. Beginning overnight on Monday and into Tuesday, we saw some heavy rains. Rain washes soil, contaminants, and pathogens, such as E. coli, into surface waters such as rivers and ponds. Although this week’s samples are all within the Class B standard, it is a reminder that most pollution in our rivers comes from the land and not from pipes, as was the case before the federal Clean Water Act went into effect. The upper Merrimack watershed is still a relatively clean and healthy river. We often say, “When it rains, it’s poor.” You may wish to wait a day or so after it rains before recreating in a surface water. 

You’ll hear from us again after the August 6 sampling day. 

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Michele L Tremblay                          Stephen C Landry
Program Manager                             Sampling Supervisor