Souhegan River Water Testing Results
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, disolved oxygen, temperature,
Weather and streamflow information was also recorded when water
samples are collected.
Previous results for 1997, 1998, and 1999 results are available in a report that can be found in local libraries.
Summaries are available here.
The current E-coli results this year are available here.
This monitoring program is conducted by trained volunteers who believe
in cleaner rivers.
Financial support for the program comes from a grant from NHDES and local conservation
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.
If you would like to help continue this monitoring effort, please contact
George May at 883-3409 or email@example.com.
September 21st results
SOUHEGAN RIVER COMES OUT OK ON BACTERIA RETESTING
The Souhegan Watershed Association retested five sites along the river in
Milford and Amherst on Thursday, September 21, and pronounced the river in
On Tuesday, September 19, the SWA conducted what was to be the final water
quality test of the year on the Souhegan and Merrimack Rivers. The SWA has
done 8 biweekly tests on a total of 26 sites on both rivers since the
beginning of June. But the test showed several surprising, abnormal E.coli
readings on the Souhegan. A dangerously high E.coli count was recorded in
the area just downstream of Milford center. The SWA looks for a reading of
88 or lower as being acceptable. The reading on Tuesday was 1370.
So volunteers were mobilized once again to retest the area to see if this
was a one time pollution discharge or a continuing problem. Luckily the
pollution seems to have abated. Tests were taken at Emerson Park, in the
center of Milford; downstream at the Swing Bridge; further downstream behind
Riverside Cemetery; and further downstream behind Lorden Plaza. The
respective E.coli counts were 248, 345, 356, and 350.
"While these results seem high, and indeed are higher than we would like to
see, they are more in line with what we would expect," according to Joanne
King, coordinator of the SWA water monitoring program. "There was almost an
inch of rain less than 24 hours before the second test, and E.coli counts go
up nearly everywhere on the river, especially in urban areas, when there’s a
heavy rain. Unfortunately, we don’t expect to see swimmable, fishable
conditions right in the center of town. These new readings are pretty much
in line with what we’ve seen for the last several years," she said.
King noted that this was the second time this year that testing has shown
dangerously high spikes in the center of Milford. There was a reading of
1250 discovered on June 27. Retesting a couple of days later again showed
that the pollution had been dissipated. “The fact that we only test every
two weeks and that we found two spikes in the same area is a cause for
concern. Somebody could be dumping waste into the river on the off days,
when we are not sampling,” she said. The SWA has indicated that they will
notify the Milford Conservation Commission and the Milford Department of
Health of their concerns.
The second area that was retested on Thursday was the Amherst Canoeport on
Boston Post Road. The Tuesday test showed a reading of 2, but that site has
never been below 88 before. Unfortunately, the retest came up with another
unacceptable, but expected, reading of 225. The SWA has been trying to find
possible causes for consistently high readings throughout the Souhegan in
Amherst but has not been able to find any manmade causes. Two of the SWA
volunteers canoed this stretch of the river last week but found no clear
evidence of human induced pollution sources. “Our present thinking is that
the high readings are natural. The river slows down, the soil is sandy, and
there are otters, muskrats and a lot of birds and wild animals nesting in
the high banks that may be causing the elevated readings,” said King.
The SWA has tested the Souhegan and Merrimack for the last several years and
pending funding, expects to continue its testing program again next year.
All of the testing is performed by trained volunteers. If you would like to
support SWA with a corporate, family or individual membership or become a
volunteer for the testing program, contact George May at 883-3409.
September 19th results
BACTERIA COUNTS ON SOUHEGAN SHOW SEVERAL SURPRISES
The final test for E.coli bacteria on the Merrimack and Souhegan Rivers for
this season produced a couple of abnormal readings on the Souhegan River.
Except for this, both rivers showed generally good results. The Merrimack
especially has had low bacteria readings almost all summer and the biweekly
test taken on Tuesday, September 19, continued this pattern of low E.coli
counts. The Merrimack has 26 Combined Sewer Overflows (CSOs) in Manchester
and 9 in Nashua. After substantial rainstorms the stormdrain runoff is
diverted from the sewage treatment plants and goes untreated into the river.
However, except after rainstorms the Merrimack is relatively free of E.coli
The Souhegan had three surprises – one good and two bad. The first reading
just downstream of the center of Milford showed very high bacteria levels,
the highest seen anyplace all season. A reading of 1370 colonies exceeds
even a scare earlier in the season when Emerson Park shot up to 1250. That
scare in June sent town officials out to take additional tests to confirm
that the bacteria count went down a couple of days later. According to
Joanne King, monitoring coordinator for SWA, “The fact that we have not one
but two consecutive sites whose counts have skyrocketed from the norm this
time indicates that there is a pollution discharge coming from a single
point. Unfortunately we do not have data for downtown Milford that may have
enabled us to better pinpoint the source. Any time we see counts this high,
we do follow up tests, in this case in the downtown area as well as
downstream, to try and get some answers. It looks as though somebody
discharged waste directly to the river shortly before the tests were taken.
Monitors will take the follow up tests on Thursday; the results should be
available on Friday and will be reported as soon as they’re available.
The second surprise was the reading at the Horseshoe, a well-known swimming
hole in Wilton. The reading here was 270, well above the very low levels
experienced all season. The monitor at this site reported that a landowner
had dumped debris and burned logs along the river since the last test two
weeks ago. The Horseshoe has had very low bacteria counts not only this
season but also last season.
The third surprise was a good one. The Amherst Canoe port on Boston Post
Road near Souhegan High School had been a popular swimming spot until last
year when the town posted it for no swimming because of the high bacteria
counts. For the last several years bacteria counts have consistently
remained way above the 88 count considered acceptable for public swimming
areas. This week’s test is the very first ever showing an acceptable
reading. It was 2.
SWA monitors canoed the Milford-Amherst section of the Souhegan recently
looking unsuccessfully for causes of the high E.coli counts that have
consistently plagued this stretch of the river. A preliminary conclusion is
that the bacteria is predominately naturally occurring caused by a good
deal of in-stream animal activity in the area . Beaver Brook comes through
the center of Amherst and has been looked at as contributing to the problem.
A special test taken from Beaver Brook showed a level of 200, higher than
acceptable but not unexpected by the monitors. A test taken slightly
downstream in the Souhegan itself showed a similar reading at 180.
The Souhegan Watershed Association and the Lower Merrimack River Local
Advisory Committee have performed these biweekly tests for the last several
years to determine the health of the rivers and to establish patterns that
may indicate possible places for remediation. One of the tests that the
volunteers perform is for E.coli bacteria, which indicates how healthy the
water is for humans. Levels above 88 may cause ear and eye infections,
diarrhea or other gastrointestinal problems among some people swimming in
A full report of the season’s testing will be compiled by the end of the
year. The report will be distributed to all watershed conservation
commissions and town libraries and is available to anyone interested.
Reports and comparisons from prior years are already available at town
September 5th results
RIVER BACTERIA COUNTS REMAIN GOOD
The bacteria levels in both the Merrimack and Souhegan Rivers have changed
only slightly since they were tested two weeks ago. They were good then and
they are good now according to volunteers from the Souhegan Watershed
Association and the Lower Merrimack River Local Advisory Committee who
perform the biweekly tests.
The organizations do a series of tests to determine the health of the rivers
and to establish trends over the season, and one of the tests – for E. Coli
bacteria - indicates how healthy the water is for humans. The SWA uses the
state standard for public swimming areas as a conservative baseline. E. Coli
bacteria levels above 88 are unacceptable because they may cause ear and eye
infections, diarrhea or other gastrointestinal problems among some of the
The Merrimack River from the Manchester line to Tyngsboro again had very low
bacteria counts this week. The uppermost site near the railroad bridge at
Goffs Falls had no detectable bacteria at all. This is the second time this
season that site had no bacteria. There was a slightly above acceptable
reading at the Tayors Falls Bridge on Canal Street in Nashua, but that was
the only reading above 88 for the entire river. Generally the Merrimack
River is quite clean.
The Souhegan River was well below the 88 baseline except for the stretch
between downtown Milford and the Boston Post Road bridge in Amherst.
Generally the stretch in downtown Milford would be expected to have high
counts because of the population density there and this week’s test was no
exception. But there was a spike to 480 behind Lorden Plaza in Milford that
may be attributable to the Milford Wastewater Treatment Plant. This
particular site is a downstream bracket for the wastewater treatment plant.
The reading went from 320 above the plant to 480 below it. This site has not
been a problem in the past and wastewater treatment plants usually release
effluent that is cleaner than the river its released to. The Merrimack
Wastewater Treatment Plant, for example, had a reading of 13 for their
effluent this week. The bracketing at the Greenville Wastewater Treatment
Plant on the Souhegan showed no increase, but that plant is being rebuilt to
bring it up to more acceptable standards. There have been problems there in
The stretch of the Souhegan through Greenville showed little cause for
concern this week. Again downtown areas usually have higher counts, but not
this time. The counts have come down to acceptable levels since the
beginning of August, perhaps because of the lack of rain that was so
pervasive earlier in the season. The flow level of the Souhegan has also
moderated in the last few weeks. The flow was right at its historical
average for this time of the year when these tests were taken. It has been
higher than average for most of this season. The flow on Tuesday was 65 CFS
(cubic feet per second) measured above Wildcat Falls in Merrimack.
The following are the bacteria results for all of the sites tested this
week. All of the bacteria results from this year and last are available on
the SWA website at www.ultranet.com/~harts/swa. The entire report on the
overall chemical health of the rivers for the last several years is
available at all watershed libraries.
The next test will be done on September 19 and will be the last test for
August 22nd results
BACTERIA COUNTS SHOW LOCAL RIVERS IN EXCELLENT SHAPE
E. Coli bacteria tests performed on 25 sites on the Souhegan and Merrimack
Rivers on August 22 by volunteers for the Souhegan Watershed Association and
Merrimack River Local Advisory Committee indicate little concern for human
safety for boaters, swimmers, bathers, waders, fishermen, or others in
contact with either river.
"This latest test gives us some of the best results we’ve had all year,"
according to George May, secretary of the SWA. "Except for the stretch of
the Souhegan from the center of Milford through Amherst not a single site on
either river had a reading above 88."
The SWA uses 88 E. Coli colonies per 100 milliliters of water as a
conservative benchmark. This is the state standard for public swimming
areas. Above this level some swimmers may experience ear and eye infections,
diarrhea or other gastrointestinal problems. Volunteers monitor the rivers
every two weeks during the summer.
"Two sites in Amherst were missed in this go-round, but both have exceeded
the 88 level on each of the five tests so far this season, so it’s safe to
assume that they would have exceeded the level again this week," said May.
"For some reason that we have not yet figured out the levels through Amherst
are always high. This has been true since we started collecting data several
The Merrimack River has had excellent results all season and continues to
show excellent results this week. The highest level between Manchester and
Tyngsboro was 50, well below the 88 level of concern. "The only time the
Merrimack has shown high E. Coli readings has been after heavy rainstorms
when the wastewater treatment plants were overwhelmed by stormwater runoff
that goes into the single sewer pipes (CSOs)," said May.
There are no CSOs on the Souhegan River, but there are 26 on the Merrimack
in Manchester and 9 in Nashua. Both cities are in the process of replacing
their single pipe systems with separate pipes for sewer and stormwater
runoff, but the process will take 20 years to complete.
The SWA has done some drain stenciling in Merrimack and in Milford to remind
people that many storm drains go directly to the river and that excess lawn
fertilizer that goes into the drains will pollute the river and kill the
fish. The SWA has also sponsored a number of schools along the Souhegan and
Merrimack in raising baby salmon in their classrooms in order to increase an
awareness of the rivers. Children in New Ipswich, Wilton, Milford, Amherst,
Merrimack, Nashua and Litchfield are all part of the US Fish & Wildlife
Adopt a Salmon Family. The Souhegan is the premier river in this area for
releasing salmon fry in order to reestablish salmon in the Merrimack
The Souhegan River has also just recently been included in the state Rivers
Management & Protection Program. The Merrimack has been included in the
state program for the last ten years, since the program’s inception.
August 8th results
RIVER BACTERIA COUNTS REMAIN STEADY
Tests performed on the Souhegan and Merrimack Rivers on August 8 indicate
little change in bacteria counts since the last tests two weeks ago. "We
have some mixed results this week, but generally bacteria levels are
remaining steady right now," according to George May, a volunteer monitor
for the Souhegan Watershed Association and Merrimack River Local Advisory
"We have very mixed results for the Merrimack River, but find it difficult
to account for spikes in the bacteria counts at Thorntons Ferry in Merrimack
and Greeley Park in Nashua. We’ve had very good tests on the Merrimack all
season and so these may be aberrations. We had only five tests on the
Merrimack this week, so we don’t have complete data. The volunteer monitor
at Greeley Park noted a rusty flow on the left of the boat ramp that may
account for that jump," said May. The Greeley Park boat ramp tested at 730
E. Coli colonies per 100 milliliters of water, up from 70 two weeks ago.
Thorntons Ferry jumped to 382 from 40 two weeks ago.
Bacteria levels above 88 are considered unsafe for public swimming areas
because they may cause ear and eye infections, diarrhea or other
gastrointestinal problems among some of the swimmers.
May noted that Dissolved Oxygen levels in both rivers has been very good,
especially compared to last year. The constant rains that we’ve had this
year has brought oxygen into the rivers and kept the river levels up and
temperatures down. Last year one could walk across the Souhegan in many
places; this week the Souhegan was flowing at almost double its historic
average. DO levels are crucial for cold water fish like the salmon and trout
in the Souhegan River.
July 25th results
BACTERIA LEVELS ON LOCAL RIVERS RETURN TO NORMAL
E. Coli bacteria levels on the Souhegan and Merrimack Rivers returned to a
more normal level on tests taken by volunteers from the Souhegan Watershed
Association and Merrimack River Local Advisory Committee, according to
George May, secretary of the SWA.
Tests taken two weeks ago were taken after a substantial rainfall and the
bacteria counts were extremely high. The recent test taken on Tuesday, July
25, came after several days of warm, dry weather. "Since we’re seeing
bacteria counts on the Souhegan increase substantially after rainstorms, it
shows that pollution is being washed into the river from roads, parking
lots, and other developed areas," according to Joanne King, coordinator for
the monitoring project. "It’s good," she said, to have data from both
extremely wet and extremely dry conditions to be able to determine where the
pollution is coming from. And if we can see where it’s coming from, we can
go to work on fixing the problem. As the population in this area of New
Hampshire continues to grow, there’s more consumption of resources and more
waste production. We can’t stop the growth in our area but we can stay
educated and come up with creative solutions to protecting our local
"The Souhegan River seems clean enough by itself, but when
we have rain, pollution levels go up, which seems to indicate bacteria and
other pollutants such as gasoline, oil, pesticides or herbicides are
being washed into the river. Storm drains all along the Souhegan must be
suspected of introducing pollution," she said. "When we look at the number
of storm drains that drain directly to the river, as we have through drain
stenciling programs, we find a good correlation between the number of drains
and the levels of pollution in these river segments during storm events."
"The present rains that we’re experiencing are probably bringing bacteria
levels back up to unhealthy levels," she said. "Swimming in the Souhegan
right now probably wouldn’t be a good idea." Bacteria levels below 88 are
considered completely safe for swimming areas. Above 88 some swimmers may
experience ear and eye infections, diarrhea or other gastrointestinal
problems. This is the level SWA uses as a guide.
The popular swimming hole at Boston Post Road near Souhegan High School
decreased to a count of 120, still slightly above the level preferred by the
SWA, but it came down from 600 in the prior test and to its lowest level in
more than a year. The swimming hole called The Horseshoe in Wilton continued
to be well within the acceptable range. It has not been above 88 all year.
Emerson Park near the Oval in Milford measured at only 70. This spot was the
site of a scare last month when the E. Coli level shot up to 1250 and
required additional testing several days later to confirm that the bacteria
levels were tolerable.
The Swing Bridge site in downtown Milford continues to have high counts
despite the dry weather, indicating that the source of pollution is instream
rather than from runoff. Low flow caused by the dam in combination with a
large population of well-fed waterfowl are most likely the source.
The Merrimack River continued to show very low E. Coli counts indicating how
clean the Merrimack has become over the last several years. Prior to the
passage of the Clean Water Act twenty-five years ago the Merrimack was on
the list of the ten dirtiest rivers in the country. There are still CSOs
dumping raw sewage into the Merrimack in Manchester and Nashua after heavy
rainstorms . But other than that the bacteria counts all along the Merrimack
are always very low.
July 11th results
RAINSTORM RAISES BACTERIA LEVELS
"The high E. coli bacteria counts on July 11th are probably the result
of a significant rainstorm twenty four hours before our sampling date,"
according to Joanne King, coordinator of the volunteer water quality
monitoring project of the Souhegan Watershed Association (SWA) and Merrimack
River Local Advisory Committee (LMRLAC), the organizations responsible for
testing on the two rivers.
"The flow on the Souhegan doubled from 80 cubic feet per second (CFS) to 170
CFS within the twenty-four hours before the test, and we sampled at its peak
flow," according to George May, secretary of the SWA and one of the
volunteer monitors. "During periods of heavy rain bacteria are washed into
the rivers and streams from all kinds of sources. It’s during heavy rains
that we experience our worst E. coli readings. Chances are that bacteria
levels have gone down by now since we haven’t had a lot of rain since the
test," said May.
Interestingly, the bacteria level at The Horseshoe, a popular swimming spot
in Wilton, was 70, well within the limits that the SWA likes to see.
Bacteria levels below 88 are considered completely safe for public swimming
areas. Higher levels may cause ear and eye infections, diarrhea or other
gastrointestinal problems among some of the swimmers. The Horseshoe was one
of only three sites on the entire length of the Souhegan that passed the
The popular swimming hole at Boston Post Road near Souhegan High School had
two readings taken. One exceeded 800 and the other 590. This site has not
passed any tests for the last couple of years and the town has posted no
"Testing under all conditions gives us a pretty good picture of the river
under all conditions, said King. "However, when, after a heavy rainfall, we
are seeing bacteria counts on the Souhegan River that are approaching the
counts seen at the Combined Sewer Overflows (CSOs) on the Merimack and
Nashua Rivers, it's a good indication that we need to be more mindful of our
land uses along the river."
"These high counts that we are seeing from runoff after a storm event are
not from ‘naturally occurring’ sources but from the way we use the land.
People could help keep the counts down in a number of ways:
- Don't feed and encourage ducks, geese and pigeons
- Maintain septic systems with an inspection and pumping every 2-3 years
- Pick up pet waste in yards and on trails
- Keep livestock manure cleaned up and away from river or catch basins
- Maintain a vegetative buffer between lawns and river
- Be aware of storm drains whose outfall is on the river and protect what
goes into them. Storm drain systems enable pollutants far from the
river’s edge to enter the river," said King.
June 27th results
BACTERIA LEVELS RISE TO UNHEALTHY LEVELS ON SOUHEGAN RIVER
Water quality testing being done by the Souhegan Watershed Association (SWA)
shows several areas of the Souhegan River where E. Coli bacteria counts have
risen since tests performed two weeks ago. George May, one of the volunteers
performing the tests, said that the frequent and steady rains over the last
couple of weeks may be washing pollution into the river and causing the
increase in bacteria. Of the sixteen sites tested along the entire length of
the river only three tested at acceptable levels. All of the rest exceeded
the 88 count considered the safety cutoff for public swimming areas.
Three sites in Greenville have increased in bacteria levels. All three sites
exceeded 200 colonies per 100 milliliter, more than double the levels of two
weeks ago. "There is very little vegetative buffer to cut any pollution
flowing toward the river as the river flows along Rte 123. But we’re
interested in finding human causes of the pollution source," said May.
"There have been spikes in the levels in this area in the past."
Most disturbingly, the E. Coli reading taken at Emerson Park next to the
Milford Oval leaped to 1250, the highest reading the SWA has ever recorded
in the four years they’ve been testing the river. "Something happened here
to cause this kind of jump. It may be a fluke reading, but officials in
Milford have been notified and are looking for the problem," said May.
The bacteria levels stayed above 88 all the way from Milford to the mouth of
the river. Finally the bacteria level dropped to 14 at the test site between
the Everett Turnpike and Rte 3 in Merrimack. This site, the popular swimming
hole at the Horseshoe in Wilton, and Highbridge in New Ipswich were the only
sites along the entire length of the river to test positively. All the
others had unacceptable bacteria contamination.
The Merrimack River is tested at nine sites between Manchester and Tyngsboro
through the Merrimack River Local Advisory Committee (LMRLAC). "Generally
speaking the Merrimack River is quite clean," said May. "There may be other
pollution problems, but bacteria is not among them. Two weeks ago the site
at Goffs Falls at the railroad bridge on the Litchfield/Manchester border
tested at 0. This week it was 30. Those are excellent numbers," he said.
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