April 2008 Water Quality Map |
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| Rainfall At Logan International Airport (inches) | |
| 3 days prior to sampling | 0.45 |
| 2 days prior to sampling | 0.01 |
| 1 day prior to sampling | 0.00 |
| Day of sampling | 0.00 |
The blue color represents river reaches that met the e. coli swimming standard of 126 colony forming units per 100 milliliters (about a teacup of water) (#/100ml). Yellow represents the reaches of the river that exceeded the swimming standard yet met the boating standard of 630/100ml. A violation of the boating standard is represented by the red color. Finally, any reaches of the river colored gray represent non-sampled areas.
Standards are set by the US Environmental Protection Agency to indicate level of health risk in freshwaters. US EPA recommends not swimming or fishing when the geometric mean of bacteria counts exceed 126/100ml, and not boating on days when the geometric mean of levels rise above 630/100ml.