Merrimack watershed bacteria results: September 6, 2022

Dear river and watershed friends,

The 2022 bacteria sampling season closed on this sixth event, September 6, 2022, with nearly 100% samples collected by 100% of its volunteers at eleven sites from Franklin to Bow.

We know that you have heard it before but it’s important to remember that the results shown below are the probable number of E. coli bacteria colonies for every 100 millilitres of water at that moment in time. We call it a snapshot because conditions at that moment are represented and anything that happened a day or so before or after this sampling date can change drastically. All warm blooded animals (including we humans) have E. coli in their guts. That means that bacteria are an indicator that poop has found its way to the water. This could be a result of stormwater runoff, failed septic systems, mis-connected pipes that are meant to transport household waste to a treatment plant, pet or wildlife waste from river watershed, and other sources.

To protect public health, State of New Hampshire designated swim beaches are not allowed to exceed 88 colonies of E. coli per 100ml. Class B waters (all of our sites are designated as Class B) shall not exceed 406 colonies. These designations do not always reflect real-time  water quality. The designation indicates what uses, e.g., swimming, fishing, should be supported by maintaining water quality.

The final sampling event results were all within the Class B standard (406 colonies per 100ml). We had only two exceedences this year with 749 colonies at Site 4 and 3,448 at Site 7 on August 9. They both resolved quickly with all sites down to double digits the following week. Even with those less-than-pleasant surprises, overall, it was a good season and we look forward to another in 2023.

You hear us say often, “When it rains, it’s poor,” which means that you may wish to wait a day or so after it rains before recreating in a surface water. 

Here are the details.

Site number and descriptionresults
#1 Pemigewasset at Route 3, Franklin74
#2 Winnipesaukee at Trestle, Franklinn/a
#3 Merrimack R. above FWWTF, Franklin31
#4 Merrimack R. below FWWTF, Franklin74
#5 Merrimack at Jamie Welch, Boscawen160
#6 Merrimack at US Route 4, Canterbury75
#7 Contoocook at Rivco, Penacook63
#8 Merrimack at Sewalls Falls, Concord41
#9 Merrimack at Manchester St., Concord74
#10 Merrimack at Blue Seal, Bow52
#11 Merrimack at Garvins Falls, Bow63

Please join us inrecognizing and thanking our Adopt-a-River Site Sponsors that make this work ppossible (listed in order of their sponsored sites).
Watts Regulator / Webster Valve
Franklin Savings Bank
Franklin Waste Water Treatment Plant (two sites)
Nelson Analytical
Essex Hydro
Aries Engineering
GZA Environmental
Granite Shore Power (two sites)

Our gratitude to Franklin Waste Water Treatment Plant for their continued support, including covering sample processing costs, and providing a safe and convenient drop-off area.

Thank you, Chantal McGuire for your sample couriering. How would we do it without you?

A big thank you and gratitude to Merrimack County Savings Bank for their generous gift to the Upper Merrimack Watershed Association to purchase equipment and supplies for the Upper Merrimack Monitoring Program, which includes annual bacteria sampling and working with fellow volunteers to collect specimens and identify them at Bug Nights each winter.

Please visit our fresh and newly designed forum at and our new, Upper Merrimack Watershed Association site at for further information. Don’t hesitate to contact us at or 603.796.2615 should you have any questions.


Michele L Tremblay                          Stephen C Landry
Program Manager                             Sampling Supervisor