BRATTLEBORO -- After showing signs of improvement earlier in the month, E. coli levels were on the rise last week in some area waterways.
A volunteer group's latest survey showed E. coli numbers that exceeded governmental safe-swimming standards at nine of 16 tested sites.
Once again, administrators said rainfall may have washed the potentially harmful bacteria into rivers and streams.
"Elevated results may have been partly a result of the significant rainfall that occurred 24-48 hours prior to volunteers collecting samples," said Laurie Callahan of Southeastern Vermont Watershed Alliance.
The alliance's first two surveys in June showed that more than half of the sites tested had E. coli numbers exceeding 235 organisms per 100 milliliters of water. That's the maximum allowable for a site to be considered "suitable for swimming," since exposure to E. coli -- which is found in fecal matter -- can cause gastrointestinal illness and other health problems.
The alliance's initial survey of the season, conducted June 13, showed two sites with as many as 1,987 E. coli. That was outdone two weeks later when two sites on the Williams River had E. coli levels that were too high for accurate measurement.
Dry weather led to a big improvement on July 11, when only four of 22 samples showed unsuitable bacterial levels. And even those problem areas exceeded health standards by less than 100.
Last week, though, showed E.
-- On the West River, four out of seven test sites registered E. coli above government standards. Those were the Brattleboro Professional Center (1,047 E. coli), South Londonderry at Rowes Road (687), South Londonderry above the Route 100 bridge (771) and Londonderry below Mountain Marketplace (548).
That was a marked difference from the July 11 survey, when all West River sites were considered safe for swimming.
-- Three of four sites on the Williams River had high E. coli levels. The worst was in Rockingham at Bartonsville Bridge (687), followed by Chester above the confluence with the Middle Branch of the Williams River (489) and Chester at the Missing Link Road bridge (326).
-- Also exceeding government standards were the Middle Branch of the Williams River in Chester (299) and Saxtons River at the Bellows Falls/Westminster "sandy beach" (261).
There were no sites tested last week on Whetstone Brook in Brattleboro, which had been a problem area in earlier surveys.
Seven sites were labeled safe for swimming in last week's survey:
-- West River: Brattleboro, Milk House Meadows (69 E. coli); Brookline bridge (190); and Ellen Ware Road swimming hole (167).
-- Rock River: Indian Love Call above the Route 30 bridge (59 and 55 in two samples).
-- Williams River: Chester, below wastewater-treatment facility (225).
-- Saxtons River: Below wastewater-treatment facility (105) and at Stickney's field swimming hole (132).
Callahan said the alliance is halfway through its water-testing season. The organization's four 2012 E. coli reports are online at https://sites.google.com/site/vtsevwa.
Mike Faher can be reached at email@example.com or 802-254-2311, ext. 275.