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This layer displays the geometric mean of certain “metals” grab samples (mg/l) collected since 1991. Older data for metals were included in the calculations as metals are collected less frequently by WDNR, hence removing values >10 years old would significantly shrink the dataset. Data were downloaded from the WDNR’s Surface Water Integrated Monitoring System (SWIMS) database on July 23rd, 2018. Any “flagged” sample was removed from the dataset (e.g. holding time exceeded, etc.). Any result that was returned as below detection limit was set to 0.001 (mg/l or µg/l, depending on common reporting units for each parameter). NR 106.06(4)(e)(3) indicates that samples below detection limit should be set to zero, but a geometric means cannot be calculated with negative values or zeros, so these samples were set to a very small positive number. |