E. Coli Levels Continue to Follow Pattern

By George May

The final test of the 2014 season showed the usual pattern for E. coli levels on the Merrimack and Souhegan Rivers. Both rivers showed little change over the course of the last month. The Merrimack remains very clean; the Souhegan less clean.

The highest E. coli count on the Merrimack showed up just above the Amoskeag Dam in Manchester. The count here was 82. The program looks for levels below 88 to signify clean water. Counts through Bedford, Litchfield, Merrimack, Hudson, and Nashua were in the 20-30 range, indicating a very clean river.

Low flow on the much smaller Souhegan River and the possible influence of heavy tornado rains in the headwaters on Saturday and an unexplained surge in flow Friday night produced much higher E. coli counts – especially in the more populated town centers. Counts rose above 88 passing through Greenville and peaked at 313 in downtown Wilton. Counts dropped through west Milford but peaked again near the Milford Oval to 248. The highest count on the river, 547.5, was measured in Amherst just downstream of the mouth of Beaver Brook. The monitor also noted a rotten egg odor coming from Beaver Brook. Downstream the counts dropped to more acceptable levels as the river passed through the more rural and slightly steeper Merrimack.

In spite of occasional blips above the acceptable E. coli levels, both rivers meet the Class B standards for swimmable and fishable rivers. It is usually only after heavy rainstorms that either of the rivers rises to dangerous swimming levels at most of the spots where people gather. With the exception of the Amherst Canoeport on Boston Post Road, all of the other normal swimming holes met acceptable levels this week also.

The Souhegan Watershed Association and Lower Merrimack River Local Advisory Committee have been monitoring these rivers for two decades and have seen major improvements. Plans are to continue to monitor again beginning in June next year. The program is always looking for volunteers to adopt a specific site or act as subs when needed. Anyone interested in more information can contact swawatertesting@gmail.com.

A map of the sites monitored on both rivers and the individual E. coli count for the season is available at nashuatelegraph.com/specialreportsrivertestresults/ and at souheganriver.org.

Professional lab technicians at the wastewater treatment plants in Manchester, Milford, Merrimack, and Nashua perform the tests for E. coli and Dissolved oxygen.

Here are this week’s E. coli numbers:

E-COLI MONITORING RESULTS FOR TESTS TAKEN ON SEPTEMBER 9, 2014

SOUHEGAN RIVER SITES:

1. Billy Ward Pond, Ashburnham #1 36.8, #2 4.1
2. SoR 333 Water Loom Pond, New Ipswich 7.5
3. SoR 320 Highbridge, New Ipswich 88.2
4. SoR 309 Above Greenville Mill Pond, Greenville 101.7
5. SoR 296 Downtown Greenville upstream of WWTP 224.7
6. SoR 291 Green Bridge off Rte 31 below Greenville WWTP NA
7. SoR 218 Below the Horseshoe, Wilton 42.8
8. SoR 210 Downtown Wilton 313.0
9. SoR 201 Pine Valley Mill, West Milford NA
10. SoR 170 Behind Hayward Field, West Milford NA
11. SoR 155 Souhegan Valley Boys and Girls Club, Milford 186.0
12. SoR 146 Swing Bridge, Milford 248.1
13. SoR 133 Riverside Cemetery, Milford 167.0
14. SoR 130 Behind Lorden Plaza, Milford 248.9
15. SoR 122 Amherst Country Club NA
16. SoR 116 Amherst Conservation land Fairway Road, Amherst 547.5
17. SoR 095 Boston Post Road Canoeport, Amherst 160.7
18. Sor 070 Seaverns Bridge, Merrimack 90.9
19. SoR 057 Indian Ledges, Merrimack 56.5
20. SoR 034 Turkey Hill Bridge, Merrimack NA
21. SoR 001 Watson Park, DW Hwy, Merrimack 24.9

MERRIMACK RIVER SITES:

1. Mer 600 Above Amoskeag Dam, Manchester 82.0

2. Mer 590 Arms Park, Manchester 52.0

3. Mer 570 Goffs Falls, Litchfield 42.8

4. Mer 560 Depot Street, Merrimack 32.7

5. Mer 550 Upstream of Souhegan River, Merrimack 23.2

6. Mer 540 Thorntons Ferry, Merrimack 25.9

7. Mer 530 Greeley Park, Nashua 24.1

8. Mer 520 Taylors Falls Bridge, Nashua 38.3

9. Mer 510 Sagamore Bridge, Hudson NA

10. Mer 500 Pheasant Lane Mall, Hudson NA

11. Mer 490 Upstream of Tyngsboro Bridge 39.9

Flow on Upper Souhegan was 17 CFS and expected flow for that date is 19

Flow on Lower Souhegan was 52 CFS and historic flow for that date is 41

Flow on Merrimack was 2080 CFS and historic flow for that date is 1450

RAINFALL - Sat afternoon, especially heavy in Souhegan headwaters. Otherwise clear.

Temperatures: Souhegan 16C; Merrimack 20C