City of Duluth public water system did not meet treatment requirements

The City of Duluth water system recently violated a drinking water standard related to turbidity.

The City of Duluth routinely monitors water for turbidity (cloudiness). This tells the city whether it is effectively filtering the water supply. Water samples on October 28, 2017 showed turbidity measurements were in excess of 1.0 Nephelometric Turbidity Units (NTU) from approximately 2:15 a.m. this morning, with a peak of approximately 17NTU at 10:45 a.m., and are now falling steadily. At the time of this notice, the levels had decreased to 0.778NTU and the city anticipates it to continue to drop.

The standard is that no more than 5 percent of samples may exceed 0.3 NTU per month, and any reading above 1NTU is considered an exceedance. Normal daily turbidity levels at the city’s water plant are about 0.025 NTU.

What should you do?

You do not need to boil your water or take other actions. The city said it does not know of any contamination, and none of its testing has shown disease-causing organisms in the drinking water.

What does this mean?

Turbidity has no health effects. However, turbidity can interfere with disinfection and provide a medium for microbial growth. The city has been monitoring the disinfection process and making adjustments necessary to prevent the presence of bacteria.

What happened? What was done?

On October 27, a powerful storm churned Lake Superior with winds in excess of 50 mph, which created waves reaching 16′ to 18’. The high waves coupled with near-record high water in Lake Superior damaged shoreline infrastructure throughout Duluth and caused massive erosion. This wave action stirred up the sediments in a large portion of the lake and created unprecedented turbidity levels.

The Lakewood Water Treatment Plant has never experienced this level of turbidity. Operations staff were able to balance out the treatment process quickly and safely, but given the large volume of the Lakewood facility any changes take several hours to pass through the entire treatment system.

For more information, please contact the 24-hour emergency line 218.393.5395.

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