The Metropolitan Pollution Control Agency (MPCA) uses E. coli as an indicator of bacteria in surface waters. E. coli is a subgroup of fecal coliform bacteria—a group of bacteria that generally originate in the intestines of warm-blooded animals. E. coli measured with standard testing will not necessarily cause illness in humans, nor does testing include all fecal pathogens that can cause illness. However, E. coli testing is an affordable method for identifying fecal contamination in surface waters. The MPCA standards for E. coli that apply to both a maximum of individual readings and a monthly geometric mean:
(1) Maximum values not to exceed 1,260 colony-forming units per 100 milliliters (cfu/100mL) in 10% or more of individual samples in a calendar month, or
(2) Monthly geometric means not to exceed 126 cfu/100mL in a calendar month
E. coli standards apply to the warmer months of April through October when people are more likely to be in contact with the water. The water quality standard refers to colony-forming units (cfu), while laboratories often report results as most-probable number (MPN). Cfu/100mL and MPN/100mL are used interchangeably. Water quality impairments are determined by calculating geometric means for aggregated data for each calendar month (e.g., calculating the geometric mean for combined June data from multiple years of monitoring). MPCA guidance places greater emphasis on monitoring during the months of June–September.
Both levels in Lake Elmo and Legion Pond are much lower than the MPCA’s standards.
Legion Pond and Lake Elmo E coli Results July 9, 2020
Legion Pond E.coli Results June 17, 2020
Lake Elmo E.coli Results June 30, 2020
Lake Elmo June and July 2020 Comparison to Previous Years: Other Water Quality Parameters
Lake Elmo Water Levels