The score for each lake is based on the geometric mean number of Escherichia coli (E. coli) collected by the beach monitoring program (Table 1-1). Lakes with more than one beach were averaged together. EPA and Minnesota guidelines state that beaches should not exceed a geometric mean of 126 organisms per 100 mL during a 30-day time period. Lower numbers of organisms indicate less risk of illnesses for lake users.
Table 1-1. Scoring for the public health portion of LAURI.
E. coli, (CFU/100mL)* | Score |
<2 (ND) | 10 |
2-10 | 9 |
11-20 | 8 |
21-35 | 7 |
36-50 | 6 |
51-65 | 5 |
66-80 | 4 |
81-100 | 3 |
101-125 | 2 |
>126 | 1 |
* The value used is the running geometric mean for the year, averaged for all the beaches on a lake.