Reader Submitted

Rivers still low, E. coli OK

Friday, September 21, 2012

The cooler water in the local rivers means that swimming season is coming to an end and there is less concern for paying attention to the E. coli levels in the rivers. The cooler temperatures also help the rivers to clean up; dissolved oxygen levels increase which helps the fish habitat. However, E. coli levels monitor the level of pollution at various sites along the river – something which should be a concern at any time of year.

This was the last test done by the trained volunteers working for the Souhegan Watershed Association for this season. The E. coli results for the week of Sept. 10 were generally acceptable and expected for this time of year. There were a couple of hot spots, both at population centers – one downstream of downtown Wilton and the other downstream of downtown Milford. Other than that, the E. coli levels were in the generally acceptable range. The best result was at the popular swimming hole at the Horseshoe in Wilton. The level here was 12.1. This site usually has good results, but two weeks ago at the last test, the result was 328. The program looks for levels less than 88. Anything above that may cause medical problems for bathers.

The new swimming spot at Watson Park in Merrimack tested at 71.2 the week of Sept. 10. Again, this site has usually been good but the last test two weeks ago showed 275.

Almost all sites tested were too high probably caused by rain beginning at the time of the tests. The rain washes bacteria into the river and can cause high counts for about three days before they come back down.

The Merrimack River between Manchester and Tyngsborough, Mass., again showed acceptable results for E. coli. This has been true all summer – and generally for the last several years – and shows how the Merrimack has been cleaned up over the years. The Merrimack River was considered one of the dirtiest rivers in the country years ago before the Clean Water Act was enacted in 1972. Secondary treatment wastewater plants were built and the river has cleaned up considerably since. A second phase of the cleanup is going on now. Both Manchester and Nashua dump raw sewage into the river when heavy rainstorms overwhelm the combined single sewer/storm drain pipes. But both cities are slowly correcting this problem.

The biggest problem with local rivers this season has been the low flow since the beginning of July. This week’s test showed little improvement in the last two weeks. Flow on the Souhegan in West Milford was 16 cubic feet per second; the expected flow here should be 35 cfs. Just above Wildcat Falls on the Souhegan, near the mouth of the river in Merrimack, the flow was 32; and the expected flow based on 70 years of data is 38 cfs. The flow in the Souhegan River is being studied by the State of New Hampshire as a pilot project for all of the rivers in the state.

Every year beginning in June, trained volunteers check on more than 20 sites along the entire length of the Souhegan River and 10 sites on the Merrimack River between Manchester and Tyngsborough. The testing program is sponsored by the Souhegan Watershed Association and Lower Merrimack River Local Advisory Committee. The E. coli and dissolved oxygen tests are performed at the Milford, Merrimack, Manchester and Nashua Wastewater Treatment facilities.

People willing to be volunteers for next year, may contact

All of the past and present E. coli levels for each site can be viewed at or at

Here are the results for tests taken Sept. 11. Numbers lower than 88 are excellent; under 126 are acceptable for swimming.

Souhegan river sites:

Billy Ward Pond, Ashburnham #1- 107.6; #2 – 2.0; Highbridge, New Ipswich – 131.4; above Greenville Mill Pond, Greenville – 129.6; downtown Greenville upstream of WWTP – 63.7; Green Bridge off Route 31 below Greenville WWTP – 80.5; below the Horseshoe, Wilton – 12.1; downtown Wilton – 344.1; Pine Valley Mill, West Milford – 84.2; Souhegan Valley Boys & Girls Club, Milford – 190.4; Riverside Cemetery, Milford – 325.5; behind Lorden Plaza, Milford – 112.6; Amherst Country Club – 209.8; Amherst conservation land Fairway Road – 149.7; mouth of Beaver Brook – 260.3; Boston Post Road Canoeport, Amherst – 85.7; Seaverns Bridge, Merrimack – 81.3; Indian Ledges, Merrimack – 47.1; Turkey Hill Bridge, Merrimack – 57.6; and Watson Park, DW Hwy, Merrimack – 71.2.

Merrimack river sites: Goffs Falls, Litchfield – 63.8; Depot Street, Merrimack – 62.0; Thorntons Ferry, Merrimack – 108.1; Greeley Park, Nashua – 51.2; Taylors Falls Bridge, Nashua – 30.1; Sagamore Bridge, Hudson – 29.9; and upstream of Tyngsboro Bridge – 15.8.

Flow on Upper Souhegan was 16 cfs and expected flow for that date is 35; flow on Lower Souhegan was 32 cfs and historic flow for that date is 38. Flow on the Merrimack was 1,840 cfs and historic flow for that date is 1,429. Temperatures: Souhegan 16C; Merrimack 20C.

– Submitted by
George May

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