​E. Coli Levels Up Again In Souhegan And Merrimack Rivers

MERRIMACK, NH — The Souhegan Watershed Association conducts volunteer water quality tests on the Souhegan and Merrimack Rivers every two weeks during the summer, according to a press statement. The luck of the draw means that many of the tests this summer have come during or after heavy rainstorms. That happened again for this week’s testing. Almost an inch of rain fell on the Friday and Saturday before the test on Tuesday.

The bacteria that were swept into the rivers by the rain then were still alive when tests were conducted on Tuesday…and that means that E. coli levels were often in an unhealthy level on both rivers. (For more information on this and other neighborhood stories, subscribe to Merrimack NH Patch to receive daily newsletters and breaking news alerts.)

The Merrimack River between Manchester and Tyngsborough typically tests at a very acceptable E. coli level. Not so at the tests two weeks ago, and again, not so this week. Only three of the sites tested at acceptable levels; four were unacceptable for public swimming. There isn’t evidence of much swimming on this stretch of the Merrimack, but the most popular spot where people do gather tested at almost 550 colonies of bacteria -and anything over 406 is dangerous to humans. Downstream, the stretch through Nashua tested below the 88 level that indicates an acceptable level.

Some of the high readings may be attributed to work being done on the Amoskeag Dam in Manchester and the resulting disturbance may be a contributing factor.

The Souhegan River is a much smaller river and so sees the effects of the rains more quickly and more severely. The upper headwaters of the Souhegan in Ashburnham and New Ipswich were at acceptable E. coli bacteria levels. From Greenville to Milford the levels were unacceptable but less than the dangerous 406 level. Through Milford and Amherst levels exceeded 406 by a factor of two. One site tested over 1000.

Once the river reached the more rural areas of Merrimack, the E. coli levels were reduced but never reached an acceptable level. At Watson Park in Merrimack, just before the river empties into the Merrimack, the level was 90.8, slightly higher than the acceptable 88 level. SWA posts a flag at Watson Park to show the water quality; this week the flag is yellow, indicating a level that may be okay, but not completely acceptable for small children or those with impaired immune systems. Swimmers ear and eye and gastrointestinal trouble may result for some people.

Besides E. coli testing, SWA monitors the dissolved oxygen levels in both rivers. This test is the best test for the general health of the river itself, for the fish, insects, habitat. This test showed both rivers to be in good health. And this has been true all summer.

It was also noted that the rivers are flowing exactly as much as they should be at this time of year. Last year rivers were in danger of losing their ability to sustain their habitat because of the very low flows. That’s all turned around.

Volunteers mentioned seeing the usual Great Blue herons, beavers, and assorted wildlife along the rivers. They also noted that the Cardinal flowers were in full bloom. Fewer people, hikers and fishermen, however, were out in the early morning along the rivers this week.

The next test will be done on August 22 and will be the final test this year. We hope to continue testing beginning in June next year and are always looking for volunteers willing to adopt a site. More information is available at www.souheganriver.org.

Here are the individual results for E. coli for this week:

Below 88 is excellent; 88-126 is okay for healthy adults; 126-406 is not acceptable; over 406 is dangerous.

E-COLI MONITORING RESULTS FOR TESTS TAKEN ON AUGUST 8, 2017

SOUHEGAN RIVER SITES:

1. Billy Ward Pond, Ashburnham #1 11.0; #2 12.1
2. SoR 333 Water Loom Pond, New Ipswich 42.8
3. SoR 320 Highbridge, New Ipswich 67.0
4. SoR 309 Above Greenville Mill Pond, Greenville 285.1
5. SoR 296 Downtown Greenville upstream of WWTP 209.8
6. SoR 291 Green Bridge off Rte 31 below Greenville WWTP 193.5
7. SoR 218 Below the Horseshoe, Wilton 125.0
8. SoR 210 Downtown Wilton 275.5
9. SoR 201 Pine Valley Mill, West Milford NA
10. SoR 170 Behind Hayward Field, West Milford 235.9
11. SoR 155 Souhegan Valley Boys and Girls Club, Milford 387.3
12. SoR 146 Swing Bridge, Milford 816.4
13. SoR 133 Riverside Cemetery, Milford 1119.9
14. SoR 130 Behind Lorden Plaza, Milford 816.4
15. SoR 122 Amherst Country Club 721.5
16. SoR 116 Amherst Conservation land Fairway Road, Amherst NA
17. SoR 095 Boston Post Road Canoeport, Amherst 172.5
18. SoR 057 Indian Ledges, Merrimack NA
19. SoR 034 Turkey Hill Bridge, Merrimack 133.3
20. SoR 001 Watson Park, Merrimack 90.8

MERRIMACK RIVER SITES:

1. Mer 600 Above Amoskeag Dam, Manchester 45.7
2. Mer 590 Arms Park, Manchester 209.8
3. Mer 580 Upstream of Piscataquog River, Manchester NA
4. Mer 570 Goffs Falls, Litchfield 547.5
5. Mer 560 Depot Street, Merrimack NA
6. Mer 550 Upstream of Souhegan River, Merrimack NA
7. Mer 540 Thorntons Ferry, Merrimack 93.3
8. Mer 530 Greeley Park, Nashua 60.9
9. Mer 520 Taylors Falls Bridge, Nashua 67.6
10. Mer 510 Sagamore Bridge, Hudson 86.0
11. Mer 500 Pheasant Lane Mall, Hudson NA
12. Mer 490 Upstream of Tyngsboro Bridge 47.3

Flow on Upper Souhegan was 25CFS. Expected flow for that date is 24

Flow on Lower Souhegan was 45CFS. Historic flow for that date is 42

Flow on Merrimack was 2440CFS. Historic flow for that date is 1510

RAINFALL: Saturday heavy showers 0.6”, Monday night 0.21”

Temperature: Souhegan 19C; Merrimack 21C

Submitted by George May.