The Souhegan Watershed Association monitors the entire length of
the Souhegan River and part of the Merrimack River for their aquatic health.
Water samples are tested for pH, phosphorus, dissolved oxygen, temperature,
Weather and streamflow information was also recorded when water
samples are collected.
Previous results, beginning in 1997, are available in reports that can be found in local libraries.
Summaries and original results are available here.
This monitoring program is conducted by trained volunteers who believe
in cleaner rivers.
Financial support for the program comes from your
memberships and donations.
If you would like to help continue this monitoring effort, please contact
George May at 883-3409 or "georgemay (at) comcast (dot) net"
or send a check to SWA, PO Box 1474, Merrimack, NH 03054.
Our E-coli samples are prepared and counted by
professionals at the local wastewater treatment plants in Greenville,
Merrimack, Milford, and Nashua on a volunteer basis.
The results are reported as the number of e-coli bacteria colonies observed under a microscope
in 100 ml of water.
Bacteria levels below 88 colonies per 100 ml. are considered safe for public swimming
areas. Anything above that level may cause ear and eye
infections, diarrhea or other gastrointestinal problems in a
percentage of swimmers. These bacteria numbers being
reported are good for only a few days.
They do indicate the general health of the river water
at a particular moment in time.
The next measurement can be considerably different, depending on water level and temperature, and
what has recently washed, flowed, or been poured into the river.
The current E-coli results this year are available here.
Dissolved oxygen is "breathed" by fish and insects that live in the water.
Dissolved Oxygen requirements for different species vary greatly, even if only fish are considered.
One of the more sensitive family
groups is trout. The lower limit for them is about 5 mg/L (or 5 ppm).
The maximum value attainable is called O2 saturation. The
concentration of O2 equal to the saturation limit in water increases with DECREASING temperature and
At 1 atmosphere pressure and 20 degrees centigrade the concentration of saturated O2 is 9.1 mg/L,
while at 1 atmosphere pressure and 25
degrees centigrade O2 is saturated at 8.2 mg/L.
The rate of oxygen usage, the rate of oxygenization (turbulence) and the rate of
mixing of the different strata of water all contribute to surface oxygen levels.
The simplified conclusion is that adequate oxygen levels
indicate a healthy, balanced river habitate.
Cumulative 2007 E-Coli Data
July 22th Report
MORE RAINS BRING MORE E. COLI
Once again high E. coli bacteria counts were recorded in the local rivers. This can be accounted for by the heavy downpours for several
days prior to the tests according to George May, president of the Souhegan Watershed Association, which has sponsored the water quality
testing program for the last twelve years. "Heavy rains like we've had wash bacteria off the land into the water and stir up sediment that may
be harboring bacteria. So when it rains hard, the bacteria counts zoom up to unacceptable levels for human contact. And that's exactly
what's happened - especially on the Souhegan," he explained.
The state standard for E. coli for public swimming beaches is 88 colonies of bacteria per 100mL. Only two sites in the headwaters of the
Souhegan River met that standard; the other 18 sites tested averaged over 1000, well beyond the acceptable level for swimming or bathing.
None of the usual swimming holes were acceptable. The Horseshoe in Wilton was 547; the Boston Post Road Canoeport near Souhegan
High School in Amherst was 1300; and the Turkey Hill Bridge area in Merrimack was 770. As the numbers exceed 88, the incidence of
gastrointestinal problems and ear and eye infections goes up. "It's tough to do during the summer, but swimmers should stay out of the
water for three days after heavy rains to avoid getting sick. At least keep your head out of the water and take a shower if you have to go
swimming," May said. He also pointed out that swimming in the Souhegan has been less attractive recently because of the sediment
washed into the water and that may help to keep the kids out. All of the monitors on Tuesday noted how muddy the water was. It looked like
coffee several noted.
The Merrimack River between Manchester and Tyngsborough usually tests better for E. coli than does the Souhegan, and this time was no
exception. The ten sites tested along the river averaged 650, better than the Souhegan, but still not acceptable. None of the sites met the 88
standard. The best was at the Greeley Park boat ramp at 107.
Two problems on the Merrimack were evident this week. An oily sheen was noted at Greeley Park and downstream near the Taylors Falls
Bridge. The Beazer land just upstream of Greeley Park oozes creosote from the groundwater into the river especially during high water.
The company has been cleaning the groundwater there for years but creosote still gets to the river. The second problem was the dumping
of raw sewage into the river both in Manchester and in Nashua. Both communities have pipes combining sewer and storm drains. Under
normal weather conditions all of the combined effluent is treated by the wastewater treatment plants; under heavy rains, there is too much for
the treatment plants to handle and the excess is dumped directly to the Merrimack without any treatment. Both cities are working to correct
the problem under mandate from the EPA Clean Water Act.
The Nashua River Watershed Association, based in Groton, MA, tests the entire length of the Nashua River and most of the tributaries once
a month during the summer. The July test was done on July xx during relatively dry weather. This accounts for the generally low E. coli levels.
Three NH sites tested higher than 88. Walker Brook in Mason was 548.
July 8th Report
LESS RAIN MEANS CLEANER, CLEARER RIVERS
"What a difference dry weather makes!" Tests for E. coli bacteria on the Souhegan and Merrimack Rivers showed drastic improvements
over the previous tests done during wet weather testing two weeks ago. "A good reading last time was 1000; this time almost all of the test
sites came in below 88," according to George May, president of the Souhegan Watershed Association. 88 is the accepted level of bacteria
for public swimming areas in NH. A reading higher than 88 would close the beach.
The Merrimack River tested as very clean. None of the sites tested between Manchester and Tyngsborough were even halfway to the 88
level. Data from past years' tests show the Merrimack River low in bacteria except during heavy rainstorms. Heavy rains can cause the
waste treatment plants in Manchester and Nashua to be overwhelmed and raw sewage is released to the river from 26 pipes in Manchester
and 8 in Nashua. May also noted that "we only test for the presence of certain pollutants. There could be lots of other things in the river that
we don't have the ability to measure. For example, the monitor at the Greeley Park boat ramp often notes an oiliness on the river that comes
from the creosote oozing into the river from the Beazer site." This is an area where the original Koppers plant creosoted telephone poles in
open pits. The area has been being cleaned up for a number of years by pumping and cleaning of ground water and has been eyed
recently for future development.
The Souhegan River also tested as very clean. A few of the sites exceeded the 88 limit, but still were low enough for no concern. The stretch
of river between Rtes 101 and 122 were slightly higher than the rest of the river but still fairly low. All of the recognized swimming spots tested
clean. The Horseshoe in Wilton was 41; the Boston Post Road Canoeport in Amherst was 83; and Turkey Hill Bridge in Merrimack was 58.
Water samples are collected every other Tuesday morning by about 30 volunteers and tests for bacteria and dissolved oxygen are done at
the Milford, Merrimack, and Nashua Wastewater Treatment Facilities. Tests for phosphorus, temperatures, and turbidity are conducted by
the volunteers at the site. The program is sponsored by the Souhegan Watershed Association and the Lower Merrimack River Local
Advisory Committee and is in its twelfth year of testing.
Monitors noted how much clearer the water was this week compared to all through the spring. Flows are also a little higher than usual this
week. A deer was spotted at the Horseshoe and mergansers near the Tyngsborough Bridge.
June 23th Report
HEAVY RAINS BRING HEAVY E. COLI READINGS
"If you went swimming recently, I hope you took a shower afterwards." The recent thunderstorms that brought heavy rain also brought very
high E. coli bacteria counts to the local rivers and ponds according to the water quality monitoring program sponsored by the Souhegan
Watershed Association and the Lower Merrimack River Local Advisory Committee. "We haven't seen bacteria readings this high in years,"
said George May, president of the SWA. "We're looking for readings of less than 88 and a count of 1000 was probably the best we saw this
week." He went on to explain that the Souhegan and Merrimack Rivers are generally clean and normally are safe for swimming but that after
any rainstorm pollution is washed into the water and bacteria levels rise. The levels remain high for about three days - the normal lifespan of
The monitoring program tests the entire 35-mile length of the Souhegan River at twenty different sites and the Merrimack River at eleven
different sites between Manchester and Tyngsborough. Tests are performed every two weeks, rain or shine.
The headwaters of the Souhegan in Ashburnham and New Ipswich had reasonably low readings for a storm event. As the river moved
along, the bacteria levels increased to about 1000 in Greenville and Wilton and to about 2000 through Milford and Amherst. By the time the
water reached the Merrimack, readings were higher than the tests were able to count. Water loaded with sediment from the Souhegan
formed its own muddy trail for some distance down the Merrimack and by the time bacteria were collected at Thorntons Ferry, just
downstream of the mouth of the Souhegan, the Merrimack River E. coli count had almost doubled.
The rivers were tested this time after thunderstorms had brought about three inches of rain within the previous 48 hours. Volunteers all
reported very high flows on both rivers, enough so that a couple of monitors had to modify their collection procedure. Ironically they reported
that the level of the Merrimack River was very low downstream of Nashua. The level of the river here is controlled by the Pawtucket Dam in
Lowell that ponds the water back upstream to Merrimack and this dam has been drawn down for maintenance all month.
Thirty volunteers collect river samples every two weeks during the summer which are then tested for E. coli bacteria, dissolved oxygen,
temperatures, phosphorus, and observations on site and at the Milford, Merrimack, and Nashua Wastewater Treatment Facilities. This is
the twelfth year that data has been collected by the program. Past results can be seen at souheganriver.org and yearly reports are
available at local libraries and conservation commissions. New volunteers are always welcome and can contact firstname.lastname@example.org
for more information.
June 10th Report
RIVER TESTING BEGINS 12th YEAR
The Souhegan Watershed Association and Lower Merrimack River Local Advisory Committee have begun water quality testing on the
Souhegan and Merrimack Rivers again this week. An all volunteer force collects water samples on a biweekly basis all summer long that
are tested at the Milford, Merrimack, and Nashua Wastewater Treatment Facilities for E. coli bacteria dissolved oxygen, phosphorus, and
The first test for E. coli this year looks remarkably similar to the results seen last year at this time. Warm weather has brought the river
temperatures almost up to air temperatures, about 74o. This means that swimming and other river activities have begun. The Merrimack
River is relatively clean as far as E. coli is concerned; several sites along the Souhegan have E. coli counts higher than acceptable.
The highest reading showed up near the Souhegan Valley Boys & Girls Club in Milford. This same site was the worst last year at this time
also. The area is close to downtown and a popular spot for pedestrians walking and bathing their dogs. A couple of headwater sites also
had readings higher than expected; River Road at Water Loom Pond in New Ipswich and above the mill pond in Greenville both tested
slightly above 100. A reading below 88 is required for safe swimming at public areas in NH.
Monitors noted how low the water level was on the Merrimack as far up as Thorntons Ferry boat ramp in Merrimack. The Pawtucket Dam in
Lowell usually ponds the water all the way back to here and again this year the owners have opened the dam to do maintenance. They
originally said that the water level would be down for only a week but they’ve now said that they don’t expect it to come back up until the end
of the month. This happened again last year and the level stayed down through July 4th and limited boating on this popular holiday.
Low water was also noted on the Souhegan, but that’s entirely due to natural causes. Water flow on local rivers is about 60% of historical
averages for this time of year. This also was true last year at this time.
The monitor at the Greeley Park boat ramp noted an oily sheen on the river there. The Beazer Company site is just upstream and has been
leaking creosote into the river ever since the site was used by Koppers to treat telephone poles in open lagoons. Big globs of tarry-looking
creosote can be seen in the water all along their property.
On a more pleasant note, one monitor spotted an unusually large 5” crayfish in the Souhegan and the Mountain Laurel is in full bloom in
Greenville. A number of monitors noted lots of wildlife at sites along both rivers.
SWA and LMRLAC monitor the Merrimack River from Manchester to Tyngsborough and the Souhegan along its entire length. Volunteers
are always wanted and can contact Karen Mattor at email@example.com if they would like to help.
These are the E. coli bacteria counts for each of the sites along both rivers. They are valid for about three days but give an indication of the
water quality in general. NA means not available or not tested. The next test will be done on June 24.
Web pages by Richard Hart.
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