Merrimack watershed bacteria results: June 30, 2026
The citizen scientist samplers of summer are here to bring you important information about the
upper Merrimack River watershed.
River quality monitoring results are here for your weekend plans.
A fun fieldwork opportunity is available for the late afternoons of July 8 and August 26 from Franklin to Bow. Contact Michele and Steve at
UMWA@MerrimackRiver.org and (landline) 603.796.2615 to learn more. Thank you.
Dear river and watershed friends,
Bacteria Day Two was June 30, 2026. Upper Merrimack Monitoring Program volunteers continued the season with ten of the eleven sites sampled from Franklin to Bow, comprising the Pemigewasset, Winnipesaukee, Contoocook, and Merrimack Rivers.
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 colonies for every 100 millilitres (ml) 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.
All samples processed were not only within the Class B standard, which is the Merrimack’s designation but were also within that of state, campground, municipal, and other swim beaches subject to inspection and testing by the State of New Hampshire. Dry weather helps keep numbers low but these low counts also mean that on June 30, there were not likely any illicit discharges, including misconnected sewage pipes.
This trend monitoring is important but is a snapshot in time. Pollutants can be present in a river system and then clear in a day or in minutes. Leonardo da Vinci said it best, “When you put your hand in a flowing stream, you touch the last that has gone before and the first of what is still to come.”
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 (colonies rounded to the nearest whole number).
| Site number and description | results |
| #1 Pemigewasset R. at Route 3, Franklin | ISQ* |
| #2 Winnipesaukee R. at Trestle, Franklin | 50 |
| #3 Merrimack R. above FWWTF, Franklin | 31 |
| #4 Merrimack R. below FWWTF, Franklin | 37 |
| #5 Merrimack R. at Jamie Welch, Boscawen | 27 |
| #6 Merrimack R. at US Route 4, Boscawen | 35 |
| #7 Contoocook R. at Rivco, Penacook | 44 |
| #8 Merrimack R. at Sewalls Falls, Concord | 36 |
| #9 Merrimack R. at Manchester St., Concord | 24 |
| #10 Merrimack R. at Blue Seal, Bow | 15 |
| #11 Merrimack R. at Garvins Falls, Bow | 34 |
*ISQ = insufficient quantity of water to process sample.
We have two mainstem and several smaller sites available so please contact us if you are interested in becoming a site sponsor.
These Adopt-a-River Site Sponsors make this work possible with sampling and their gifts, which cover costs. Please join us in recognizing and thanking them.
Winnipesaukee River Basin Program (two sites)
Watts Regulator / Webster Valve
GZA Environmental
Granite Shore Power (two sites)
Gideon Asen LLC
Essex Hydro
Elektrisola
Aries Engineering
Our gratitude to the Winnipesaukee River Basin Program for not only being samplers but for covering the considerable costs of laboratory processing and for providing a safe and convenient drop-off area.
Thank you to the Department of Health and Human Services Public Health Laboratory who does a wonderful job processing our samples.
A big thank you to Chantal McGuire who continues to make a major trek from her homeplace to Franklin and then to Concord to assure that samples are transported quickly and under controlled conditions.
Did you know that the Upper Merrimack Monitoring program is staffed and managed 100% by volunteers? This means that throughout the year, volunteers organize and perform activities including water sampling, collect benthic macroinvertebrates to gauge long-term river health, and work nights in a laboratory to identify those “bugs.” If you want to learn more or get involved, please contact Michele and Steve (see below for contact information).
Volunteers will take their next samples on Tuesday, July 14, 2026.
Please visit our forum at MerrimackRiver.org/forum and the Upper Merrimack Watershed Association site MerrimackRiver.org for further information. Don’t hesitate to contact us at UMMP@MerrimackRiver.org or 603.796.2615 (landline) should you have questions.
Sincerely,
Michele L Tremblay, Program Manager
Stephen C. Landry, Sampling Supervisor