MARQUETTE - City officials said Monday they have been largely unable to identify the source of elevated E. coli levels on city beaches.
"I've been going through all the data and everything and, honestly, I cannot pinpoint a direct source," said Curt Goodman, head of the city's Water/Wastewater Department. "All I know is that the E. coli levels are elevated a little bit over the last 10 years."
Unusually high levels of E. coli, verified through regular testing of the lake water, have forced the closure of two city beaches this month.
Marquette’s South Beach, seen here, is one of two Marquette beaches clsoed this month due to unusually high levels of E. coli bacteria. City officials have been unable to identify a specific source for the contamination. (Journal photo by Matt Keiser)
Twice each week, city staff draws three water samples from each city beach. If the three samples average more than 300 parts E. coli per 100 ml of water, state regulations indicate a beach must be closed.
On July 20, the city closed South Beach when the results from the previous day's test showed an average of 552 parts E. coli; exactly one week later, North Beach closed after a reading of 484.
In each case, Goodman immediately ordered a new test, from which results typically take 24 hours.
The exceedances are clear outliers in the data, however. In the weeks leading up to the exceedance at North Beach, only one test showed an average in excess of 100 parts. Numbers are similar at South Beach.
Still, numbers across the board seem slightly higher this year, according to Goodman, who said E. coli can enter the water from a number of possible sources, including sewer overflow, animal waste or stormwater runoff. The city has been unable to link the test results to any of those possible scenarios, he said.
Carl Lindquist, the executive director of the Superior Watershed Partnership, told the city commission Monday both exceedances were recorded following rain.
At the start of Monday's regular meeting, the commission added a discussion of the recent test results to the agenda and later turned to Goodman and Lindquist for explanation.
"We've taken over 2,000 samples and I can count on one hand how many advisories we've put out," Goodman told the group.
Prior to the meeting, Goodman said he was looking into the possibility that unusually warm temperatures in Lake Superior may be contributing to the climbing numbers. Current water temperatures, he said, are about 5 degrees warmer than last year.
"We have looked at the characteristics of our beaches," he said. "None of those have proven to be a direct cause. We are looking at some of the beach characteristics a little bit more."
He said South Beach, for instance, is low and guarded against natural elements. Because of that, the sand is more likely to remain damp and stationary, providing a better environment for bacteria.
The beach testing done in Marquette is not mandated by the state, but is done in conjunction with a grant from the Michigan Department of Environmental Quality and Goodman said the city operates the only testing operation in Marquette County.
The city's historical beach testing data can be found online at www.deq.state.mi.us/ beach.
Goodman also said Marquette is one of eight communities in the state that is taking place in an upcoming rapid test pilot program. The new test, he said, would allow officials to get E. coli test results in about three hours.
Kyle Whitney can be reached at 906-228-2500, ext. 250.