The outdoor swimming season may be winding down, but volunteers with the nonprofit organization White River Partnership still have a couple of more weeks before wrapping up a 13th season of water quality testing at popular swimming holes. Volunteers have been testing water quality at swimming holes and the mouths of major tributaries around the White River Watershed every other Wednesday since May 29. Their last day of 2013 testing will be September 18.
The volunteer testers are measuring bacteria counts in the water. The EPA “swimmable” standard is 235 bacteria colonies/100 mL sample. The most recent posted data was collected on August 21. On that day, none of the 21 test sites had bacteria levels beyond the swimmable standard. However, Vermont had fair weather in the 24 hours preceding those tests.
On its website, the White River Partnership cautions:
As a rule of thumb, avoid swimming or tubing in the White River during and immediately after a rain event because there is an increased risk of exposure to bacterial contamination.
Why is this type of monitoring necessary? Here's what the White River Partnership has to say:
Bacterial monitoring is a practical method to determine the potential health risk of water exposure. Bacteria are microscopic, single-celled organisms that can be found in virtually any environment. Bacterial indicators of pollution are the species found in the intestines of warmblooded animals, including humans, where many pathogens also originate. Indicator bacteria in a waterway come from many sources, including animal droppings, faulty or leaking septic or sewage systems, stormwater runoff, and disturbed sediments.
According to data collected over the past few years, the swimming holes tested in the White River watershed generally had good water quality during dry weather, but some elevated levels of bacteria were detected during or immediately after rainfall.
In its 2012 Water Quality Report, the most recent report summarizing a full season of data, the White River Partnership concluded the effects of Tropical Storm Irene may still be influencing water quality.
Tropical Storm Irene may be impacting bacteria levels —At most sites, bacteria levels were a little higher than in previous years, especially on rainy sampling days. This may be due to the removal of vegetation along the riverbanks, which slows down and traps runoff, during and after Irene. Continued monitoring will reveal whether bacteria levels drop as riverbanks revegetate in coming years.
In addition to water quality testing, the White River Partnership also conducts riverbank restoration projects and river cleanups. September is River Cleanup Month in Vermont, and this year the White River Partnership is focusing on lingering trash deposited by floodwaters from Tropical Storm Irene. The groups says over 150,000 pounds of Irene-related trash has been removed from along the White River to date, yet more remains.