The Flathead City-County Health Department conducted water tests on Echo Lake after residents shared concerns about the floodwaters carrying sewage into the lake from nearby septic systems.
County health officer Joe Russell said the water samples initially showed higher-than-average Escherichia coli (E. coli) levels in Causeway Bay, leading officials to declare the area unsuitable for recreational swimming on July 15.
The test results showed 158 E. coli organisms per 100 milliliter of water in Causeway Bay – located in the southern area of the lake – at that time. Samples from the rest of the lake found the bacteria as well, but in much lower levels.
However, subsequent tests from July 18 showed lower levels of the bacteria, Russell said this week, and the area is safe for recreational use again. The tests showed E. coli present in the water, but at safe levels.
“The new results would indicate that you can use that part (of the lake) for recreation,” Russell said.
E. coli is often the culprit behind travelers’ diarrhea and has been known to cause food-borne outbreaks in the United States, according to the U.S. Centers for Disease Control and Prevention.
The bacteria could come from multiple sources, Russell said, though it is usually associated with humans. It can be found in the intestines of any warm-blooded animal, he said, as well as the soil.
“You just have a lot of sources of bacteria,” Russell said. “And just because there’s bacteria doesn’t mean there’s disease.”
Echo Lake has experienced high floodwaters this spring due to unusually high snowpack levels, and Russell said the health department would keep watching the lake’s fill levels to determine if further tests are necessary.
“We think the whole process of filling is slowing down,” he said.
The fact that the test results showed low E. coli levels on July 18 means the high ratios found on July 14 were an acute incident instead of a chronic issue, Russell said.
In an acute incident, bacteria and other mechanical processes eat up the E. coli bacteria in a natural process, Russell said.
Septic systems and concern about leaking sewage compelled the health department to take the tests, Russell said, but those concerns were largely unfounded.
Since Echo Lake is located in a floodplain, permitted septic systems around the lake are located at least 50 feet from the lake’s high water mark. Some systems are 100 feet away from historic high water marks, Russell said.
“Most of the systems under permit won’t be inundated with floodwater,” he said.
However, there are unpermitted septic systems on Echo Lake, which also prompted the health department’s water testing.
“There are certainly old septic systems that may not meet today’s standards,” Russell said.
Along with the testing, Russell said the department completed surveillance of the lake and septic systems to ensure the high levels of bacteria are not a chronic problem.
Russell also stressed that bacteria can be found in almost every sample of lake water and the microorganisms are found everywhere. He discouraged consuming untreated lake water from anywhere at any time.
A map of the health department’s tests on Echo Lake water samples can be found on the department’s website, www.flatheadhealth.org.