July 28

 

SWIMMING NOT RECOMMENDED TILL RIVER IMPROVES

 

Sporadic, localized rain showers, some heavy, right before testing occurred produced uneven E. coli counts in the Souhegan and Merrimack Rivers this week. After large rainstorms, bacteria is washed into the rivers from riverbanks and storm drains. Generally the bacteria die after three days of clear weather following moderately high counts. Both rivers showed vastly different results this week.

 

The Merrimack River between Manchester and Tyngsborough tested clean, but the Souhegan River had very high bacteria counts when tested this Tuesday morning.  Counts on the Merrimack averaged only 53 colonies of bacteria per hundred milliliters of water. Counts less than 88 are considered healthy for swimming. The Souhegan, however, averaged much higher. Some sites between Wilton and Milford were even higher than the 2419 maximum that the test can measure. That the bacteria counts improved as the river continued downstream indicates that heavy localized thunderstorms on Monday in the Lyndeborough area were responsible for the pollution. By the time the river reached Watson Park at the mouth of the river, the bacteria level dropped to 110, still higher than the 88 level recommended for swimming at public beaches in NH – but probably OK for healthy adults.

 

A high count was measured on the Merrimack River at Arms Park in Manchester, but lower counts nearby meant that large flocks of ducks at the park were responsible for that aberration.

 

The Souhegan Watershed Association tests the two rivers every two weeks during the summer. This season has been unusual because of heavy rainstorms right before the tests were taken. This is what causes the high bacteria counts and it’s completely natural.

The Souhegan is a smaller river that meanders seriously from Milford through Amherst and Merrimack. This means that the river becomes longer, has more riverbank per gallon of water, which allows for more bacterial riverbank surface and storm drains to drain into the river. There is less water to dilute the pollution.

 

Normally the Merrimack River tests very clean for bacteria and has for the last several years. There may be other contaminants in the river, but E. coli doesn’t seem to be a concern. E. coli bacteria are an indicator species for other bacteria that would cause gatrointestinal problems for humans swimming in the water. Counts higher than 88 colonies of bacteria are the safe limit for swimming areas. Counts between 88 and 126 may be OK for healthy adults; counts higher than 126 should be avoided.

 

The flow on both rivers is still slightly higher than its expected, historical average for this time of year. It has been most of the summer. Dissolved oxygen levels, which indicate the general health of the river itself, continue to be very acceptable, even high for this time of year.

 

Monitors noted the abundance of flowering plants and animal tracks along the riverbanks. Cardinal flowers, especially noted, are in full bloom.

 

Besides the 30 monitors that have adopted their sites and deliver their samples and data, certified lab personnel in the Greenville, Milford, Merrimack, Manchester, and Nashua waste treatment facilities perform the tests for dissolved oxygen and E. coli bacteria.

 

Tests are collected every two weeks during the summer. The next test will be done on August 11; results will be available the following day. The results for individual sites tested on both rivers is available at souheganriver.org.

 

Here are this week’s results:

 

E-COLI MONITORING RESULTS FOR TESTS TAKEN ON JULY 28, 2015

 

SOUHEGAN RIVER SITES:

 

  1. Billy Ward Pond, Ashburnham  #1  1.0,  #2  3.1

  2. SoR  333  Water Loom Pond, New Ipswich  60.9

  3. SoR  320  Highbridge, New Ipswich  547.5

  4. SoR  309  Above Greenville Mill Pond, Greenville  >2419.6

  5. SoR  296  Downtown Greenville upstream of WWTP  325.5

  6. SoR  291  Green Bridge off Rte 31 below Greenville WWTP   1203.3

  7. SoR  218  Below the Horseshoe, Wilton   1203.3

  8. SoR  210  Downtown Wilton  2419.6

  9. SoR  201  Pine Valley Mill, West Milford   >2419.6

  10. SoR  170  Behind Hayward Field, West Milford    NA

  11. SoR  155  Souhegan Valley Boys and Girls Club, Milford  >2419.6

  12. SoR  146  Swing Bridge, Milford  1986.3

  13. SoR  133  Riverside Cemetery, Milford   1413.6

  14. SoR  130  Behind Lorden Plaza, Milford  1413.6

  15. SoR  122  Amherst Country Club  1413.6

  16. SoR  116  Amherst Conservation land Fairway Road, Amherst   NA

  17. SoR  095  Boston Post Road Canoeport, Amherst  1046.2

  18. Sor   070   Seaverns Bridge, Merrimack  613.1

  19. SoR  057  Indian Ledges, Merrimack  NA

  20. SoR  034  Turkey Hill Bridge, Merrimack   198.9

  21. SoR  001   Watson Park, DW Hwy, Merrimack  110.0

 

 

MERRIMACK RIVER SITES:

 

1.      Mer  600  Above Amoskeag Dam, Manchester  18.7

2.      Mer  590  Arms Park, Manchester  410.6

3.      Mer  570  Goffs Falls, Litchfield  70.6

4.      Mer  560  Depot Street, Merrimack   49.6

5.      Mer  550  Upstream of Souhegan River, Merrimack   NA

6.      Mer  540  Thorntons Ferry, Merrimack  135.4

7.      Mer  530  Greeley Park, Nashua  NA

8.      Mer  520  Taylors Falls Bridge, Nashua   NA

9.      Mer  510  Sagamore Bridge, Hudson  20.6

10.  Mer  500  Pheasant Lane Mall, Hudson    NA

11.  Mer  490  Upstream of Tyngsboro Bridge  22.6

 

                                   

Flow on Upper Souhegan was 121 CFS and expected flow for that date is 39

Flow on Lower Souhegan was 106 CFS and historic flow for that date is 48

Flow on Merrimack was 2600 CFS (fluctuating) and historic flow for that date is 1660

RAINFALL -  Showers with occasional bursts prior to test date; heavier rain upper river

River temperature: Souhegan 21C;  Merrimack 23C

 

DISSOLVED OXYGEN RESULTS FOR TESTS TAKEN ON JULY 28, 2015

 

SOUHEGAN RIVER SITES:

 

  1. Billy Ward Pond, Ashburnham  #1  7.13,  #2  7.35

  2. SoR  333  River Road above Water Loom Pond, New Ipswich  6.87

  3. SoR  320  Highbridge, New Ipswich  8.22

  4. SoR  309  Above Greenville Mill Pond, Greenville  7.97

  5. SoR  296  Downtown Greenville upstream of WWTP  8.36

  6. SoR  291  Green Bridge off Rte 31 below Greenville WWTP  8.40

  7. SoR  218  Below the Horseshoe, Wilton   9.18

  8. SoR  210  Downtown Wilton  9.05

  9. SoR  201  Pine Valley Mill, West Milford   8.95

  10. SoR  170  Behind Hayward Field, West Milford  NA 

  11. SoR  155  Souhegan Valley Boys and Girls Club, Milford  8.09

  12. SoR  146  Swing Bridge, Milford  8.26

  13. SoR  133  Riverside Cemetery, Milford   8.56

  14. SoR  130  Behind Lorden Plaza, Milford  8.51

  15. SoR  122  Amherst Country Club  8.47

  16. SoR  116  Amherst Conservation land Fairway Road, Amherst    NA

  17. SoR  095  Boston Post Road Canoeport, Amherst  7.88

  18. Sor   070   Seaverns Bridge, Merrimack 7.51

  19. SoR  057  Indian Ledges, Merrimack  NA

  20. SoR  034  Turkey Hill Bridge, Merrimack   7.92

  21. SoR  001   Watson Park, DW Hwy, Merrimack  8.80

 

 

MERRIMACK RIVER SITES:

 

12.  Mer  600  Above Amoskeag Dam, Manchester  7.28

13.  Mer  590  Arms Park, Manchester  8.11

14.  Mer  570  Goffs Falls, Litchfield  7.68

15.  Mer  560  Depot Street, Merrimack    7.92

16.  Mer  550  Upstream of Souhegan River, Merrimack   NA

17.  Mer  540  Thorntons Ferry, Merrimack  NA

18.  Mer  530  Greeley Park, Nashua  NA

19.  Mer  520  Taylors Falls Bridge, Nashua   NA

20.  Mer  510  Sagamore Bridge, Hudson  8.30

21.  Mer  500  Pheasant Lane Mall, Hudson    NA

22.  Mer  490  Upstream of Tyngsboro Bridge  8.08